reorg: cli/js/compiler/, move more API to cli/js/web/ (#4310)

- moves compiler implementation to "cli/js/compiler/" directory
- moves more APIs to "cli/js/web":
    * "console.ts"
    * "console_table.ts"
    * "performance.ts"
    * "timers.ts"
    * "workers.ts"
- removes some dead code from "cli/js/"

9 files changed, 1830 insertions, 0 deletions

diff --git a/cli/js/compiler/api.ts b/cli/js/compiler/api.ts
new file mode 100644
index 000000000..e6e1d5eee
--- /dev/null
+++ b/cli/js/compiler/api.ts
@@ -0,0 +1,409 @@
+// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
+
+// This file contains the runtime APIs which will dispatch work to the internal
+// compiler within Deno.
+
+import { DiagnosticItem } from "../diagnostics.ts";
+import * as util from "../util.ts";
+import * as runtimeCompilerOps from "../ops/runtime_compiler.ts";
+
+/** A specific subset TypeScript compiler options that can be supported by
+ * the Deno TypeScript compiler. */
+export interface CompilerOptions {
+  /** Allow JavaScript files to be compiled. Defaults to `true`. */
+  allowJs?: boolean;
+
+  /** Allow default imports from modules with no default export. This does not
+   * affect code emit, just typechecking. Defaults to `false`. */
+  allowSyntheticDefaultImports?: boolean;
+
+  /** Allow accessing UMD globals from modules. Defaults to `false`. */
+  allowUmdGlobalAccess?: boolean;
+
+  /** Do not report errors on unreachable code. Defaults to `false`. */
+  allowUnreachableCode?: boolean;
+
+  /** Do not report errors on unused labels. Defaults to `false` */
+  allowUnusedLabels?: boolean;
+
+  /** Parse in strict mode and emit `"use strict"` for each source file.
+   * Defaults to `true`. */
+  alwaysStrict?: boolean;
+
+  /** Base directory to resolve non-relative module names. Defaults to
+   * `undefined`. */
+  baseUrl?: string;
+
+  /** Report errors in `.js` files. Use in conjunction with `allowJs`. Defaults
+   * to `false`. */
+  checkJs?: boolean;
+
+  /** Generates corresponding `.d.ts` file. Defaults to `false`. */
+  declaration?: boolean;
+
+  /** Output directory for generated declaration files. */
+  declarationDir?: string;
+
+  /** Generates a source map for each corresponding `.d.ts` file. Defaults to
+   * `false`. */
+  declarationMap?: boolean;
+
+  /** Provide full support for iterables in `for..of`, spread and
+   * destructuring when targeting ES5 or ES3.  Defaults to `false`. */
+  downlevelIteration?: boolean;
+
+  /** Emit a UTF-8 Byte Order Mark (BOM) in the beginning of output files.
+   * Defaults to `false`. */
+  emitBOM?: boolean;
+
+  /** Only emit `.d.ts` declaration files. Defaults to `false`. */
+  emitDeclarationOnly?: boolean;
+
+  /** Emit design-type metadata for decorated declarations in source. See issue
+   * [microsoft/TypeScript#2577](https://github.com/Microsoft/TypeScript/issues/2577)
+   * for details. Defaults to `false`. */
+  emitDecoratorMetadata?: boolean;
+
+  /** Emit `__importStar` and `__importDefault` helpers for runtime babel
+   * ecosystem compatibility and enable `allowSyntheticDefaultImports` for type
+   * system compatibility. Defaults to `true`. */
+  esModuleInterop?: boolean;
+
+  /** Enables experimental support for ES decorators. Defaults to `false`. */
+  experimentalDecorators?: boolean;
+
+  /** Emit a single file with source maps instead of having a separate file.
+   * Defaults to `false`. */
+  inlineSourceMap?: boolean;
+
+  /** Emit the source alongside the source maps within a single file; requires
+   * `inlineSourceMap` or `sourceMap` to be set. Defaults to `false`. */
+  inlineSources?: boolean;
+
+  /** Perform additional checks to ensure that transpile only would be safe.
+   * Defaults to `false`. */
+  isolatedModules?: boolean;
+
+  /** Support JSX in `.tsx` files: `"react"`, `"preserve"`, `"react-native"`.
+   * Defaults to `"react"`. */
+  jsx?: "react" | "preserve" | "react-native";
+
+  /** Specify the JSX factory function to use when targeting react JSX emit,
+   * e.g. `React.createElement` or `h`. Defaults to `React.createElement`. */
+  jsxFactory?: string;
+
+  /** Resolve keyof to string valued property names only (no numbers or
+   * symbols). Defaults to `false`. */
+  keyofStringsOnly?: string;
+
+  /** Emit class fields with ECMAScript-standard semantics. Defaults to `false`.
+   * Does not apply to `"esnext"` target. */
+  useDefineForClassFields?: boolean;
+
+  /** List of library files to be included in the compilation.  If omitted,
+   * then the Deno main runtime libs are used. */
+  lib?: string[];
+
+  /** The locale to use to show error messages. */
+  locale?: string;
+
+  /** Specifies the location where debugger should locate map files instead of
+   * generated locations. Use this flag if the `.map` files will be located at
+   * run-time in a different location than the `.js` files. The location
+   * specified will be embedded in the source map to direct the debugger where
+   * the map files will be located. Defaults to `undefined`. */
+  mapRoot?: string;
+
+  /** Specify the module format for the emitted code.  Defaults to
+   * `"esnext"`. */
+  module?:
+    | "none"
+    | "commonjs"
+    | "amd"
+    | "system"
+    | "umd"
+    | "es6"
+    | "es2015"
+    | "esnext";
+
+  /** Do not generate custom helper functions like `__extends` in compiled
+   * output. Defaults to `false`. */
+  noEmitHelpers?: boolean;
+
+  /** Report errors for fallthrough cases in switch statement. Defaults to
+   * `false`. */
+  noFallthroughCasesInSwitch?: boolean;
+
+  /** Raise error on expressions and declarations with an implied any type.
+   * Defaults to `true`. */
+  noImplicitAny?: boolean;
+
+  /** Report an error when not all code paths in function return a value.
+   * Defaults to `false`. */
+  noImplicitReturns?: boolean;
+
+  /** Raise error on `this` expressions with an implied `any` type. Defaults to
+   * `true`. */
+  noImplicitThis?: boolean;
+
+  /** Do not emit `"use strict"` directives in module output. Defaults to
+   * `false`. */
+  noImplicitUseStrict?: boolean;
+
+  /** Do not add triple-slash references or module import targets to the list of
+   * compiled files. Defaults to `false`. */
+  noResolve?: boolean;
+
+  /** Disable strict checking of generic signatures in function types. Defaults
+   * to `false`. */
+  noStrictGenericChecks?: boolean;
+
+  /** Report errors on unused locals. Defaults to `false`. */
+  noUnusedLocals?: boolean;
+
+  /** Report errors on unused parameters. Defaults to `false`. */
+  noUnusedParameters?: boolean;
+
+  /** Redirect output structure to the directory. This only impacts
+   * `Deno.compile` and only changes the emitted file names.  Defaults to
+   * `undefined`. */
+  outDir?: string;
+
+  /** List of path mapping entries for module names to locations relative to the
+   * `baseUrl`. Defaults to `undefined`. */
+  paths?: Record<string, string[]>;
+
+  /** Do not erase const enum declarations in generated code. Defaults to
+   * `false`. */
+  preserveConstEnums?: boolean;
+
+  /** Remove all comments except copy-right header comments beginning with
+   * `/*!`. Defaults to `true`. */
+  removeComments?: boolean;
+
+  /** Include modules imported with `.json` extension. Defaults to `true`. */
+  resolveJsonModule?: boolean;
+
+  /** Specifies the root directory of input files. Only use to control the
+   * output directory structure with `outDir`. Defaults to `undefined`. */
+  rootDir?: string;
+
+  /** List of _root_ folders whose combined content represent the structure of
+   * the project at runtime. Defaults to `undefined`. */
+  rootDirs?: string[];
+
+  /** Generates corresponding `.map` file. Defaults to `false`. */
+  sourceMap?: boolean;
+
+  /** Specifies the location where debugger should locate TypeScript files
+   * instead of source locations. Use this flag if the sources will be located
+   * at run-time in a different location than that at design-time. The location
+   * specified will be embedded in the sourceMap to direct the debugger where
+   * the source files will be located. Defaults to `undefined`. */
+  sourceRoot?: string;
+
+  /** Enable all strict type checking options. Enabling `strict` enables
+   * `noImplicitAny`, `noImplicitThis`, `alwaysStrict`, `strictBindCallApply`,
+   * `strictNullChecks`, `strictFunctionTypes` and
+   * `strictPropertyInitialization`. Defaults to `true`. */
+  strict?: boolean;
+
+  /** Enable stricter checking of the `bind`, `call`, and `apply` methods on
+   * functions. Defaults to `true`. */
+  strictBindCallApply?: boolean;
+
+  /** Disable bivariant parameter checking for function types. Defaults to
+   * `true`. */
+  strictFunctionTypes?: boolean;
+
+  /** Ensure non-undefined class properties are initialized in the constructor.
+   * This option requires `strictNullChecks` be enabled in order to take effect.
+   * Defaults to `true`. */
+  strictPropertyInitialization?: boolean;
+
+  /** In strict null checking mode, the `null` and `undefined` values are not in
+   * the domain of every type and are only assignable to themselves and `any`
+   * (the one exception being that `undefined` is also assignable to `void`). */
+  strictNullChecks?: boolean;
+
+  /** Suppress excess property checks for object literals. Defaults to
+   * `false`. */
+  suppressExcessPropertyErrors?: boolean;
+
+  /** Suppress `noImplicitAny` errors for indexing objects lacking index
+   * signatures. */
+  suppressImplicitAnyIndexErrors?: boolean;
+
+  /** Specify ECMAScript target version. Defaults to `esnext`. */
+  target?:
+    | "es3"
+    | "es5"
+    | "es6"
+    | "es2015"
+    | "es2016"
+    | "es2017"
+    | "es2018"
+    | "es2019"
+    | "es2020"
+    | "esnext";
+
+  /** List of names of type definitions to include. Defaults to `undefined`.
+   *
+   * The type definitions are resolved according to the normal Deno resolution
+   * irrespective of if sources are provided on the call.  Like other Deno
+   * modules, there is no "magical" resolution.  For example:
+   *
+   *      Deno.compile(
+   *        "./foo.js",
+   *        undefined,
+   *        {
+   *          types: [ "./foo.d.ts", "https://deno.land/x/example/types.d.ts" ]
+   *        }
+   *      );
+   *
+   */
+  types?: string[];
+}
+
+/** Internal function to just validate that the specifier looks relative, that
+ * it starts with `./`. */
+function checkRelative(specifier: string): string {
+  return specifier.match(/^([\.\/\\]|https?:\/{2}|file:\/{2})/)
+    ? specifier
+    : `./${specifier}`;
+}
+
+/** The results of a transpile only command, where the `source` contains the
+ * emitted source, and `map` optionally contains the source map.
+ */
+export interface TranspileOnlyResult {
+  source: string;
+  map?: string;
+}
+
+/** Takes a set of TypeScript sources and resolves with a map where the key was
+ * the original file name provided in sources and the result contains the
+ * `source` and optionally the `map` from the transpile operation. This does no
+ * type checking and validation, it effectively "strips" the types from the
+ * file.
+ *
+ *      const results =  await Deno.transpileOnly({
+ *        "foo.ts": `const foo: string = "foo";`
+ *      });
+ *
+ * @param sources A map where the key is the filename and the value is the text
+ *                to transpile.  The filename is only used in the transpile and
+ *                not resolved, for example to fill in the source name in the
+ *                source map.
+ * @param options An option object of options to send to the compiler. This is
+ *                a subset of ts.CompilerOptions which can be supported by Deno.
+ *                Many of the options related to type checking and emitting
+ *                type declaration files will have no impact on the output.
+ */
+export async function transpileOnly(
+  sources: Record<string, string>,
+  options: CompilerOptions = {}
+): Promise<Record<string, TranspileOnlyResult>> {
+  util.log("Deno.transpileOnly", { sources: Object.keys(sources), options });
+  const payload = {
+    sources,
+    options: JSON.stringify(options)
+  };
+  const result = await runtimeCompilerOps.transpile(payload);
+  return JSON.parse(result);
+}
+
+/** Takes a root module name, any optionally a record set of sources. Resolves
+ * with a compiled set of modules.  If just a root name is provided, the modules
+ * will be resolved as if the root module had been passed on the command line.
+ *
+ * If sources are passed, all modules will be resolved out of this object, where
+ * the key is the module name and the value is the content.  The extension of
+ * the module name will be used to determine the media type of the module.
+ *
+ *      const [ maybeDiagnostics1, output1 ] = await Deno.compile("foo.ts");
+ *
+ *      const [ maybeDiagnostics2, output2 ] = await Deno.compile("/foo.ts", {
+ *        "/foo.ts": `export * from "./bar.ts";`,
+ *        "/bar.ts": `export const bar = "bar";`
+ *      });
+ *
+ * @param rootName The root name of the module which will be used as the
+ *                 "starting point".  If no `sources` is specified, Deno will
+ *                 resolve the module externally as if the `rootName` had been
+ *                 specified on the command line.
+ * @param sources An optional key/value map of sources to be used when resolving
+ *                modules, where the key is the module name, and the value is
+ *                the source content.  The extension of the key will determine
+ *                the media type of the file when processing.  If supplied,
+ *                Deno will not attempt to resolve any modules externally.
+ * @param options An optional object of options to send to the compiler. This is
+ *                a subset of ts.CompilerOptions which can be supported by Deno.
+ */
+export async function compile(
+  rootName: string,
+  sources?: Record<string, string>,
+  options: CompilerOptions = {}
+): Promise<[DiagnosticItem[] | undefined, Record<string, string>]> {
+  const payload = {
+    rootName: sources ? rootName : checkRelative(rootName),
+    sources,
+    options: JSON.stringify(options),
+    bundle: false
+  };
+  util.log("Deno.compile", {
+    rootName: payload.rootName,
+    sources: !!sources,
+    options
+  });
+  const result = await runtimeCompilerOps.compile(payload);
+  return JSON.parse(result);
+}
+
+/** Takes a root module name, and optionally a record set of sources. Resolves
+ * with a single JavaScript string that is like the output of a `deno bundle`
+ * command.  If just a root name is provided, the modules will be resolved as if
+ * the root module had been passed on the command line.
+ *
+ * If sources are passed, all modules will be resolved out of this object, where
+ * the key is the module name and the value is the content. The extension of the
+ * module name will be used to determine the media type of the module.
+ *
+ *      const [ maybeDiagnostics1, output1 ] = await Deno.bundle("foo.ts");
+ *
+ *      const [ maybeDiagnostics2, output2 ] = await Deno.bundle("/foo.ts", {
+ *        "/foo.ts": `export * from "./bar.ts";`,
+ *        "/bar.ts": `export const bar = "bar";`
+ *      });
+ *
+ * @param rootName The root name of the module which will be used as the
+ *                 "starting point".  If no `sources` is specified, Deno will
+ *                 resolve the module externally as if the `rootName` had been
+ *                 specified on the command line.
+ * @param sources An optional key/value map of sources to be used when resolving
+ *                modules, where the key is the module name, and the value is
+ *                the source content.  The extension of the key will determine
+ *                the media type of the file when processing.  If supplied,
+ *                Deno will not attempt to resolve any modules externally.
+ * @param options An optional object of options to send to the compiler. This is
+ *                a subset of ts.CompilerOptions which can be supported by Deno.
+ */
+export async function bundle(
+  rootName: string,
+  sources?: Record<string, string>,
+  options: CompilerOptions = {}
+): Promise<[DiagnosticItem[] | undefined, string]> {
+  const payload = {
+    rootName: sources ? rootName : checkRelative(rootName),
+    sources,
+    options: JSON.stringify(options),
+    bundle: true
+  };
+  util.log("Deno.bundle", {
+    rootName: payload.rootName,
+    sources: !!sources,
+    options
+  });
+  const result = await runtimeCompilerOps.compile(payload);
+  return JSON.parse(result);
+}
diff --git a/cli/js/compiler/bootstrap.ts b/cli/js/compiler/bootstrap.ts
new file mode 100644
index 000000000..d4642d041
--- /dev/null
+++ b/cli/js/compiler/bootstrap.ts
@@ -0,0 +1,52 @@
+// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
+
+import { CompilerHostTarget, Host } from "./host.ts";
+import { ASSETS } from "./sourcefile.ts";
+import { getAsset } from "./util.ts";
+
+// NOTE: target doesn't really matter here,
+// this is in fact a mock host created just to
+// load all type definitions and snapshot them.
+const host = new Host({
+  target: CompilerHostTarget.Main,
+  writeFile(): void {}
+});
+const options = host.getCompilationSettings();
+
+// This is a hacky way of adding our libs to the libs available in TypeScript()
+// as these are internal APIs of TypeScript which maintain valid libs
+ts.libs.push("deno.ns", "deno.window", "deno.worker", "deno.shared_globals");
+ts.libMap.set("deno.ns", "lib.deno.ns.d.ts");
+ts.libMap.set("deno.window", "lib.deno.window.d.ts");
+ts.libMap.set("deno.worker", "lib.deno.worker.d.ts");
+ts.libMap.set("deno.shared_globals", "lib.deno.shared_globals.d.ts");
+
+// this pre-populates the cache at snapshot time of our library files, so they
+// are available in the future when needed.
+host.getSourceFile(`${ASSETS}/lib.deno.ns.d.ts`, ts.ScriptTarget.ESNext);
+host.getSourceFile(`${ASSETS}/lib.deno.window.d.ts`, ts.ScriptTarget.ESNext);
+host.getSourceFile(`${ASSETS}/lib.deno.worker.d.ts`, ts.ScriptTarget.ESNext);
+host.getSourceFile(
+  `${ASSETS}/lib.deno.shared_globals.d.ts`,
+  ts.ScriptTarget.ESNext
+);
+
+/**
+ * This function spins up TS compiler and loads all available libraries
+ * into memory (including ones specified above).
+ *
+ * Used to generate the foundational AST for all other compilations, so it can
+ * be cached as part of the snapshot and available to speed up startup.
+ */
+export const TS_SNAPSHOT_PROGRAM = ts.createProgram({
+  rootNames: [`${ASSETS}/bootstrap.ts`],
+  options,
+  host
+});
+
+/** A module loader which is concatenated into bundle files.
+ *
+ * We read all static assets during the snapshotting process, which is
+ * why this is located in compiler_bootstrap.
+ */
+export const SYSTEM_LOADER = getAsset("system_loader.js");
diff --git a/cli/js/compiler/bundler.ts b/cli/js/compiler/bundler.ts
new file mode 100644
index 000000000..ab987a7fc
--- /dev/null
+++ b/cli/js/compiler/bundler.ts
@@ -0,0 +1,103 @@
+// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
+
+import { SYSTEM_LOADER } from "./bootstrap.ts";
+import { commonPath, normalizeString, CHAR_FORWARD_SLASH } from "./util.ts";
+import { assert } from "../util.ts";
+
+/** Local state of what the root exports are of a root module. */
+let rootExports: string[] | undefined;
+
+/** Take a URL and normalize it, resolving relative path parts. */
+function normalizeUrl(rootName: string): string {
+  const match = /^(\S+:\/{2,3})(.+)$/.exec(rootName);
+  if (match) {
+    const [, protocol, path] = match;
+    return `${protocol}${normalizeString(
+      path,
+      false,
+      "/",
+      code => code === CHAR_FORWARD_SLASH
+    )}`;
+  } else {
+    return rootName;
+  }
+}
+
+/** Given a root name, contents, and source files, enrich the data of the
+ * bundle with a loader and re-export the exports of the root name. */
+export function buildBundle(
+  rootName: string,
+  data: string,
+  sourceFiles: readonly ts.SourceFile[]
+): string {
+  // when outputting to AMD and a single outfile, TypeScript makes up the module
+  // specifiers which are used to define the modules, and doesn't expose them
+  // publicly, so we have to try to replicate
+  const sources = sourceFiles.map(sf => sf.fileName);
+  const sharedPath = commonPath(sources);
+  rootName = normalizeUrl(rootName)
+    .replace(sharedPath, "")
+    .replace(/\.\w+$/i, "");
+  // If one of the modules requires support for top-level-await, TypeScript will
+  // emit the execute function as an async function.  When this is the case we
+  // need to bubble up the TLA to the instantiation, otherwise we instantiate
+  // synchronously.
+  const hasTla = data.match(/execute:\sasync\sfunction\s/);
+  let instantiate: string;
+  if (rootExports && rootExports.length) {
+    instantiate = hasTla
+      ? `const __exp = await __instantiateAsync("${rootName}");\n`
+      : `const __exp = __instantiate("${rootName}");\n`;
+    for (const rootExport of rootExports) {
+      if (rootExport === "default") {
+        instantiate += `export default __exp["${rootExport}"];\n`;
+      } else {
+        instantiate += `export const ${rootExport} = __exp["${rootExport}"];\n`;
+      }
+    }
+  } else {
+    instantiate = hasTla
+      ? `await __instantiateAsync("${rootName}");\n`
+      : `__instantiate("${rootName}");\n`;
+  }
+  return `${SYSTEM_LOADER}\n${data}\n${instantiate}`;
+}
+
+/** Set the rootExports which will by the `emitBundle()` */
+export function setRootExports(program: ts.Program, rootModule: string): void {
+  // get a reference to the type checker, this will let us find symbols from
+  // the AST.
+  const checker = program.getTypeChecker();
+  // get a reference to the main source file for the bundle
+  const mainSourceFile = program.getSourceFile(rootModule);
+  assert(mainSourceFile);
+  // retrieve the internal TypeScript symbol for this AST node
+  const mainSymbol = checker.getSymbolAtLocation(mainSourceFile);
+  if (!mainSymbol) {
+    return;
+  }
+  rootExports = checker
+    .getExportsOfModule(mainSymbol)
+    // .getExportsOfModule includes type only symbols which are exported from
+    // the module, so we need to try to filter those out.  While not critical
+    // someone looking at the bundle would think there is runtime code behind
+    // that when there isn't.  There appears to be no clean way of figuring that
+    // out, so inspecting SymbolFlags that might be present that are type only
+    .filter(
+      sym =>
+        sym.flags & ts.SymbolFlags.Class ||
+        !(
+          sym.flags & ts.SymbolFlags.Interface ||
+          sym.flags & ts.SymbolFlags.TypeLiteral ||
+          sym.flags & ts.SymbolFlags.Signature ||
+          sym.flags & ts.SymbolFlags.TypeParameter ||
+          sym.flags & ts.SymbolFlags.TypeAlias ||
+          sym.flags & ts.SymbolFlags.Type ||
+          sym.flags & ts.SymbolFlags.Namespace ||
+          sym.flags & ts.SymbolFlags.InterfaceExcludes ||
+          sym.flags & ts.SymbolFlags.TypeParameterExcludes ||
+          sym.flags & ts.SymbolFlags.TypeAliasExcludes
+        )
+    )
+    .map(sym => sym.getName());
+}
diff --git a/cli/js/compiler/host.ts b/cli/js/compiler/host.ts
new file mode 100644
index 000000000..8032d83b3
--- /dev/null
+++ b/cli/js/compiler/host.ts
@@ -0,0 +1,329 @@
+// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
+
+import { ASSETS, MediaType, SourceFile } from "./sourcefile.ts";
+import { OUT_DIR, WriteFileCallback, getAsset } from "./util.ts";
+import { cwd } from "../ops/fs/dir.ts";
+import { assert, notImplemented } from "../util.ts";
+import * as util from "../util.ts";
+
+/** Specifies the target that the host should use to inform the TypeScript
+ * compiler of what types should be used to validate the program against. */
+export enum CompilerHostTarget {
+  /** The main isolate library, where the main program runs. */
+  Main = "main",
+  /** The runtime API library. */
+  Runtime = "runtime",
+  /** The worker isolate library, where worker programs run. */
+  Worker = "worker"
+}
+
+export interface CompilerHostOptions {
+  /** Flag determines if the host should assume a single bundle output. */
+  bundle?: boolean;
+
+  /** Determines what the default library that should be used when type checking
+   * TS code. */
+  target: CompilerHostTarget;
+
+  /** A function to be used when the program emit occurs to write out files. */
+  writeFile: WriteFileCallback;
+}
+
+export interface ConfigureResponse {
+  ignoredOptions?: string[];
+  diagnostics?: ts.Diagnostic[];
+}
+
+/** Options that need to be used when generating a bundle (either trusted or
+ * runtime). */
+export const defaultBundlerOptions: ts.CompilerOptions = {
+  allowJs: true,
+  inlineSourceMap: false,
+  module: ts.ModuleKind.System,
+  outDir: undefined,
+  outFile: `${OUT_DIR}/bundle.js`,
+  // disabled until we have effective way to modify source maps
+  sourceMap: false
+};
+
+/** Default options used by the compiler Host when compiling. */
+export const defaultCompileOptions: ts.CompilerOptions = {
+  allowJs: false,
+  allowNonTsExtensions: true,
+  checkJs: false,
+  esModuleInterop: true,
+  jsx: ts.JsxEmit.React,
+  module: ts.ModuleKind.ESNext,
+  outDir: OUT_DIR,
+  resolveJsonModule: true,
+  sourceMap: true,
+  strict: true,
+  stripComments: true,
+  target: ts.ScriptTarget.ESNext
+};
+
+/** Options that need to be used when doing a runtime (non bundled) compilation */
+export const defaultRuntimeCompileOptions: ts.CompilerOptions = {
+  outDir: undefined
+};
+
+/** Default options used when doing a transpile only. */
+export const defaultTranspileOptions: ts.CompilerOptions = {
+  esModuleInterop: true,
+  module: ts.ModuleKind.ESNext,
+  sourceMap: true,
+  scriptComments: true,
+  target: ts.ScriptTarget.ESNext
+};
+
+/** Options that either do nothing in Deno, or would cause undesired behavior
+ * if modified. */
+const ignoredCompilerOptions: readonly string[] = [
+  "allowSyntheticDefaultImports",
+  "baseUrl",
+  "build",
+  "composite",
+  "declaration",
+  "declarationDir",
+  "declarationMap",
+  "diagnostics",
+  "downlevelIteration",
+  "emitBOM",
+  "emitDeclarationOnly",
+  "esModuleInterop",
+  "extendedDiagnostics",
+  "forceConsistentCasingInFileNames",
+  "help",
+  "importHelpers",
+  "incremental",
+  "inlineSourceMap",
+  "inlineSources",
+  "init",
+  "isolatedModules",
+  "listEmittedFiles",
+  "listFiles",
+  "mapRoot",
+  "maxNodeModuleJsDepth",
+  "module",
+  "moduleResolution",
+  "newLine",
+  "noEmit",
+  "noEmitHelpers",
+  "noEmitOnError",
+  "noLib",
+  "noResolve",
+  "out",
+  "outDir",
+  "outFile",
+  "paths",
+  "preserveSymlinks",
+  "preserveWatchOutput",
+  "pretty",
+  "rootDir",
+  "rootDirs",
+  "showConfig",
+  "skipDefaultLibCheck",
+  "skipLibCheck",
+  "sourceMap",
+  "sourceRoot",
+  "stripInternal",
+  "target",
+  "traceResolution",
+  "tsBuildInfoFile",
+  "types",
+  "typeRoots",
+  "version",
+  "watch"
+];
+
+export class Host implements ts.CompilerHost {
+  private readonly _options = defaultCompileOptions;
+
+  private _target: CompilerHostTarget;
+
+  private _writeFile: WriteFileCallback;
+
+  private _getAsset(filename: string): SourceFile {
+    const lastSegment = filename.split("/").pop()!;
+    const url = ts.libMap.has(lastSegment)
+      ? ts.libMap.get(lastSegment)!
+      : lastSegment;
+    const sourceFile = SourceFile.get(url);
+    if (sourceFile) {
+      return sourceFile;
+    }
+    const name = url.includes(".") ? url : `${url}.d.ts`;
+    const sourceCode = getAsset(name);
+    return new SourceFile({
+      url,
+      filename: `${ASSETS}/${name}`,
+      mediaType: MediaType.TypeScript,
+      sourceCode
+    });
+  }
+
+  /* Deno specific APIs */
+
+  /** Provides the `ts.HostCompiler` interface for Deno. */
+  constructor({ bundle = false, target, writeFile }: CompilerHostOptions) {
+    this._target = target;
+    this._writeFile = writeFile;
+    if (bundle) {
+      // options we need to change when we are generating a bundle
+      Object.assign(this._options, defaultBundlerOptions);
+    }
+  }
+
+  /** Take a configuration string, parse it, and use it to merge with the
+   * compiler's configuration options.  The method returns an array of compiler
+   * options which were ignored, or `undefined`. */
+  configure(path: string, configurationText: string): ConfigureResponse {
+    util.log("compiler::host.configure", path);
+    assert(configurationText);
+    const { config, error } = ts.parseConfigFileTextToJson(
+      path,
+      configurationText
+    );
+    if (error) {
+      return { diagnostics: [error] };
+    }
+    const { options, errors } = ts.convertCompilerOptionsFromJson(
+      config.compilerOptions,
+      cwd()
+    );
+    const ignoredOptions: string[] = [];
+    for (const key of Object.keys(options)) {
+      if (
+        ignoredCompilerOptions.includes(key) &&
+        (!(key in this._options) || options[key] !== this._options[key])
+      ) {
+        ignoredOptions.push(key);
+        delete options[key];
+      }
+    }
+    Object.assign(this._options, options);
+    return {
+      ignoredOptions: ignoredOptions.length ? ignoredOptions : undefined,
+      diagnostics: errors.length ? errors : undefined
+    };
+  }
+
+  /** Merge options into the host's current set of compiler options and return
+   * the merged set. */
+  mergeOptions(...options: ts.CompilerOptions[]): ts.CompilerOptions {
+    Object.assign(this._options, ...options);
+    return Object.assign({}, this._options);
+  }
+
+  /* TypeScript CompilerHost APIs */
+
+  fileExists(_fileName: string): boolean {
+    return notImplemented();
+  }
+
+  getCanonicalFileName(fileName: string): string {
+    return fileName;
+  }
+
+  getCompilationSettings(): ts.CompilerOptions {
+    util.log("compiler::host.getCompilationSettings()");
+    return this._options;
+  }
+
+  getCurrentDirectory(): string {
+    return "";
+  }
+
+  getDefaultLibFileName(_options: ts.CompilerOptions): string {
+    util.log("compiler::host.getDefaultLibFileName()");
+    switch (this._target) {
+      case CompilerHostTarget.Main:
+      case CompilerHostTarget.Runtime:
+        return `${ASSETS}/lib.deno.window.d.ts`;
+      case CompilerHostTarget.Worker:
+        return `${ASSETS}/lib.deno.worker.d.ts`;
+    }
+  }
+
+  getNewLine(): string {
+    return "\n";
+  }
+
+  getSourceFile(
+    fileName: string,
+    languageVersion: ts.ScriptTarget,
+    onError?: (message: string) => void,
+    shouldCreateNewSourceFile?: boolean
+  ): ts.SourceFile | undefined {
+    util.log("compiler::host.getSourceFile", fileName);
+    try {
+      assert(!shouldCreateNewSourceFile);
+      const sourceFile = fileName.startsWith(ASSETS)
+        ? this._getAsset(fileName)
+        : SourceFile.get(fileName);
+      assert(sourceFile != null);
+      if (!sourceFile.tsSourceFile) {
+        assert(sourceFile.sourceCode != null);
+        sourceFile.tsSourceFile = ts.createSourceFile(
+          fileName.startsWith(ASSETS) ? sourceFile.filename : fileName,
+          sourceFile.sourceCode,
+          languageVersion
+        );
+        delete sourceFile.sourceCode;
+      }
+      return sourceFile.tsSourceFile;
+    } catch (e) {
+      if (onError) {
+        onError(String(e));
+      } else {
+        throw e;
+      }
+      return undefined;
+    }
+  }
+
+  readFile(_fileName: string): string | undefined {
+    return notImplemented();
+  }
+
+  resolveModuleNames(
+    moduleNames: string[],
+    containingFile: string
+  ): Array<ts.ResolvedModuleFull | undefined> {
+    util.log("compiler::host.resolveModuleNames", {
+      moduleNames,
+      containingFile
+    });
+    return moduleNames.map(specifier => {
+      const url = SourceFile.getUrl(specifier, containingFile);
+      const sourceFile = specifier.startsWith(ASSETS)
+        ? this._getAsset(specifier)
+        : url
+        ? SourceFile.get(url)
+        : undefined;
+      if (!sourceFile) {
+        return undefined;
+      }
+      return {
+        resolvedFileName: sourceFile.url,
+        isExternalLibraryImport: specifier.startsWith(ASSETS),
+        extension: sourceFile.extension
+      };
+    });
+  }
+
+  useCaseSensitiveFileNames(): boolean {
+    return true;
+  }
+
+  writeFile(
+    fileName: string,
+    data: string,
+    _writeByteOrderMark: boolean,
+    _onError?: (message: string) => void,
+    sourceFiles?: readonly ts.SourceFile[]
+  ): void {
+    util.log("compiler::host.writeFile", fileName);
+    this._writeFile(fileName, data, sourceFiles);
+  }
+}
diff --git a/cli/js/compiler/imports.ts b/cli/js/compiler/imports.ts
new file mode 100644
index 000000000..077303b61
--- /dev/null
+++ b/cli/js/compiler/imports.ts
@@ -0,0 +1,183 @@
+// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
+
+import { MediaType, SourceFile, SourceFileJson } from "./sourcefile.ts";
+import { normalizeString, CHAR_FORWARD_SLASH } from "./util.ts";
+import { cwd } from "../ops/fs/dir.ts";
+import { assert } from "../util.ts";
+import * as util from "../util.ts";
+import * as compilerOps from "../ops/compiler.ts";
+
+/** Resolve a path to the final path segment passed. */
+function resolvePath(...pathSegments: string[]): string {
+  let resolvedPath = "";
+  let resolvedAbsolute = false;
+
+  for (let i = pathSegments.length - 1; i >= -1 && !resolvedAbsolute; i--) {
+    let path: string;
+
+    if (i >= 0) path = pathSegments[i];
+    else path = cwd();
+
+    // Skip empty entries
+    if (path.length === 0) {
+      continue;
+    }
+
+    resolvedPath = `${path}/${resolvedPath}`;
+    resolvedAbsolute = path.charCodeAt(0) === CHAR_FORWARD_SLASH;
+  }
+
+  // At this point the path should be resolved to a full absolute path, but
+  // handle relative paths to be safe (might happen when cwd() fails)
+
+  // Normalize the path
+  resolvedPath = normalizeString(
+    resolvedPath,
+    !resolvedAbsolute,
+    "/",
+    code => code === CHAR_FORWARD_SLASH
+  );
+
+  if (resolvedAbsolute) {
+    if (resolvedPath.length > 0) return `/${resolvedPath}`;
+    else return "/";
+  } else if (resolvedPath.length > 0) return resolvedPath;
+  else return ".";
+}
+
+/** Resolve a relative specifier based on the referrer.  Used when resolving
+ * modules internally within the runtime compiler API. */
+function resolveSpecifier(specifier: string, referrer: string): string {
+  if (!specifier.startsWith(".")) {
+    return specifier;
+  }
+  const pathParts = referrer.split("/");
+  pathParts.pop();
+  let path = pathParts.join("/");
+  path = path.endsWith("/") ? path : `${path}/`;
+  return resolvePath(path, specifier);
+}
+
+/** Ops to Rust to resolve modules' URLs. */
+export function resolveModules(
+  specifiers: string[],
+  referrer?: string
+): string[] {
+  util.log("compiler_imports::resolveModules", { specifiers, referrer });
+  return compilerOps.resolveModules(specifiers, referrer);
+}
+
+/** Ops to Rust to fetch modules meta data. */
+function fetchSourceFiles(
+  specifiers: string[],
+  referrer?: string
+): Promise<SourceFileJson[]> {
+  util.log("compiler_imports::fetchSourceFiles", { specifiers, referrer });
+  return compilerOps.fetchSourceFiles(specifiers, referrer);
+}
+
+/** Given a filename, determine the media type based on extension.  Used when
+ * resolving modules internally in a runtime compile. */
+function getMediaType(filename: string): MediaType {
+  const maybeExtension = /\.([a-zA-Z]+)$/.exec(filename);
+  if (!maybeExtension) {
+    util.log(`!!! Could not identify valid extension: "${filename}"`);
+    return MediaType.Unknown;
+  }
+  const [, extension] = maybeExtension;
+  switch (extension.toLowerCase()) {
+    case "js":
+      return MediaType.JavaScript;
+    case "jsx":
+      return MediaType.JSX;
+    case "json":
+      return MediaType.Json;
+    case "ts":
+      return MediaType.TypeScript;
+    case "tsx":
+      return MediaType.TSX;
+    case "wasm":
+      return MediaType.Wasm;
+    default:
+      util.log(`!!! Unknown extension: "${extension}"`);
+      return MediaType.Unknown;
+  }
+}
+
+/** Recursively process the imports of modules from within the supplied sources,
+ * generating `SourceFile`s of any imported files.
+ *
+ * Specifiers are supplied in an array of tuples where the first is the
+ * specifier that will be requested in the code and the second is the specifier
+ * that should be actually resolved. */
+export function processLocalImports(
+  sources: Record<string, string>,
+  specifiers: Array<[string, string]>,
+  referrer?: string,
+  processJsImports = false
+): string[] {
+  if (!specifiers.length) {
+    return [];
+  }
+  const moduleNames = specifiers.map(
+    referrer
+      ? ([, specifier]): string => resolveSpecifier(specifier, referrer)
+      : ([, specifier]): string => specifier
+  );
+  for (let i = 0; i < moduleNames.length; i++) {
+    const moduleName = moduleNames[i];
+    assert(moduleName in sources, `Missing module in sources: "${moduleName}"`);
+    const sourceFile =
+      SourceFile.get(moduleName) ||
+      new SourceFile({
+        url: moduleName,
+        filename: moduleName,
+        sourceCode: sources[moduleName],
+        mediaType: getMediaType(moduleName)
+      });
+    sourceFile.cache(specifiers[i][0], referrer);
+    if (!sourceFile.processed) {
+      processLocalImports(
+        sources,
+        sourceFile.imports(processJsImports),
+        sourceFile.url,
+        processJsImports
+      );
+    }
+  }
+  return moduleNames;
+}
+
+/** Recursively process the imports of modules, generating `SourceFile`s of any
+ * imported files.
+ *
+ * Specifiers are supplied in an array of tuples where the first is the
+ * specifier that will be requested in the code and the second is the specifier
+ * that should be actually resolved. */
+export async function processImports(
+  specifiers: Array<[string, string]>,
+  referrer?: string,
+  processJsImports = false
+): Promise<string[]> {
+  if (!specifiers.length) {
+    return [];
+  }
+  const sources = specifiers.map(([, moduleSpecifier]) => moduleSpecifier);
+  const resolvedSources = resolveModules(sources, referrer);
+  const sourceFiles = await fetchSourceFiles(resolvedSources, referrer);
+  assert(sourceFiles.length === specifiers.length);
+  for (let i = 0; i < sourceFiles.length; i++) {
+    const sourceFileJson = sourceFiles[i];
+    const sourceFile =
+      SourceFile.get(sourceFileJson.url) || new SourceFile(sourceFileJson);
+    sourceFile.cache(specifiers[i][0], referrer);
+    if (!sourceFile.processed) {
+      await processImports(
+        sourceFile.imports(processJsImports),
+        sourceFile.url,
+        processJsImports
+      );
+    }
+  }
+  return resolvedSources;
+}
diff --git a/cli/js/compiler/sourcefile.ts b/cli/js/compiler/sourcefile.ts
new file mode 100644
index 000000000..cfa09cde3
--- /dev/null
+++ b/cli/js/compiler/sourcefile.ts
@@ -0,0 +1,189 @@
+// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
+
+import { getMappedModuleName, parseTypeDirectives } from "./type_directives.ts";
+import { assert, log } from "../util.ts";
+
+// Warning! The values in this enum are duplicated in `cli/msg.rs`
+// Update carefully!
+export enum MediaType {
+  JavaScript = 0,
+  JSX = 1,
+  TypeScript = 2,
+  TSX = 3,
+  Json = 4,
+  Wasm = 5,
+  Unknown = 6
+}
+
+/** The shape of the SourceFile that comes from the privileged side */
+export interface SourceFileJson {
+  url: string;
+  filename: string;
+  mediaType: MediaType;
+  sourceCode: string;
+}
+
+export const ASSETS = "$asset$";
+
+/** Returns the TypeScript Extension enum for a given media type. */
+function getExtension(fileName: string, mediaType: MediaType): ts.Extension {
+  switch (mediaType) {
+    case MediaType.JavaScript:
+      return ts.Extension.Js;
+    case MediaType.JSX:
+      return ts.Extension.Jsx;
+    case MediaType.TypeScript:
+      return fileName.endsWith(".d.ts") ? ts.Extension.Dts : ts.Extension.Ts;
+    case MediaType.TSX:
+      return ts.Extension.Tsx;
+    case MediaType.Json:
+      return ts.Extension.Json;
+    case MediaType.Wasm:
+      // Custom marker for Wasm type.
+      return ts.Extension.Js;
+    case MediaType.Unknown:
+    default:
+      throw TypeError(
+        `Cannot resolve extension for "${fileName}" with mediaType "${MediaType[mediaType]}".`
+      );
+  }
+}
+
+/** A self registering abstraction of source files. */
+export class SourceFile {
+  extension!: ts.Extension;
+  filename!: string;
+
+  /** An array of tuples which represent the imports for the source file.  The
+   * first element is the one that will be requested at compile time, the
+   * second is the one that should be actually resolved.  This provides the
+   * feature of type directives for Deno. */
+  importedFiles?: Array<[string, string]>;
+
+  mediaType!: MediaType;
+  processed = false;
+  sourceCode?: string;
+  tsSourceFile?: ts.SourceFile;
+  url!: string;
+
+  constructor(json: SourceFileJson) {
+    if (SourceFile._moduleCache.has(json.url)) {
+      throw new TypeError("SourceFile already exists");
+    }
+    Object.assign(this, json);
+    this.extension = getExtension(this.url, this.mediaType);
+    SourceFile._moduleCache.set(this.url, this);
+  }
+
+  /** Cache the source file to be able to be retrieved by `moduleSpecifier` and
+   * `containingFile`. */
+  cache(moduleSpecifier: string, containingFile?: string): void {
+    containingFile = containingFile || "";
+    let innerCache = SourceFile._specifierCache.get(containingFile);
+    if (!innerCache) {
+      innerCache = new Map();
+      SourceFile._specifierCache.set(containingFile, innerCache);
+    }
+    innerCache.set(moduleSpecifier, this);
+  }
+
+  /** Process the imports for the file and return them. */
+  imports(processJsImports: boolean): Array<[string, string]> {
+    if (this.processed) {
+      throw new Error("SourceFile has already been processed.");
+    }
+    assert(this.sourceCode != null);
+    // we shouldn't process imports for files which contain the nocheck pragma
+    // (like bundles)
+    if (this.sourceCode.match(/\/{2}\s+@ts-nocheck/)) {
+      log(`Skipping imports for "${this.filename}"`);
+      return [];
+    }
+
+    const preProcessedFileInfo = ts.preProcessFile(
+      this.sourceCode,
+      true,
+      this.mediaType === MediaType.JavaScript ||
+        this.mediaType === MediaType.JSX
+    );
+    this.processed = true;
+    const files = (this.importedFiles = [] as Array<[string, string]>);
+
+    function process(references: Array<{ fileName: string }>): void {
+      for (const { fileName } of references) {
+        files.push([fileName, fileName]);
+      }
+    }
+
+    const {
+      importedFiles,
+      referencedFiles,
+      libReferenceDirectives,
+      typeReferenceDirectives
+    } = preProcessedFileInfo;
+    const typeDirectives = parseTypeDirectives(this.sourceCode);
+    if (typeDirectives) {
+      for (const importedFile of importedFiles) {
+        files.push([
+          importedFile.fileName,
+          getMappedModuleName(importedFile, typeDirectives)
+        ]);
+      }
+    } else if (
+      !(
+        !processJsImports &&
+        (this.mediaType === MediaType.JavaScript ||
+          this.mediaType === MediaType.JSX)
+      )
+    ) {
+      process(importedFiles);
+    }
+    process(referencedFiles);
+    // built in libs comes across as `"dom"` for example, and should be filtered
+    // out during pre-processing as they are either already cached or they will
+    // be lazily fetched by the compiler host.  Ones that contain full files are
+    // not filtered out and will be fetched as normal.
+    process(
+      libReferenceDirectives.filter(
+        ({ fileName }) => !ts.libMap.has(fileName.toLowerCase())
+      )
+    );
+    process(typeReferenceDirectives);
+    return files;
+  }
+
+  /** A cache of all the source files which have been loaded indexed by the
+   * url. */
+  private static _moduleCache: Map<string, SourceFile> = new Map();
+
+  /** A cache of source files based on module specifiers and containing files
+   * which is used by the TypeScript compiler to resolve the url */
+  private static _specifierCache: Map<
+    string,
+    Map<string, SourceFile>
+  > = new Map();
+
+  /** Retrieve a `SourceFile` based on a `moduleSpecifier` and `containingFile`
+   * or return `undefined` if not preset. */
+  static getUrl(
+    moduleSpecifier: string,
+    containingFile: string
+  ): string | undefined {
+    const containingCache = this._specifierCache.get(containingFile);
+    if (containingCache) {
+      const sourceFile = containingCache.get(moduleSpecifier);
+      return sourceFile && sourceFile.url;
+    }
+    return undefined;
+  }
+
+  /** Retrieve a `SourceFile` based on a `url` */
+  static get(url: string): SourceFile | undefined {
+    return this._moduleCache.get(url);
+  }
+
+  /** Determine if a source file exists or not */
+  static has(url: string): boolean {
+    return this._moduleCache.has(url);
+  }
+}
diff --git a/cli/js/compiler/ts_global.d.ts b/cli/js/compiler/ts_global.d.ts
new file mode 100644
index 000000000..7b9d84c7a
--- /dev/null
+++ b/cli/js/compiler/ts_global.d.ts
@@ -0,0 +1,26 @@
+// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
+
+// This scopes the `ts` namespace globally, which is where it exists at runtime
+// when building Deno, but the `typescript/lib/typescript.d.ts` is defined as a
+// module.
+
+// Warning! This is a magical import. We don't want to have multiple copies of
+// typescript.d.ts around the repo, there's already one in
+// deno_typescript/typescript/lib/typescript.d.ts. Ideally we could simply point
+// to that in this import specifier, but "cargo package" is very strict and
+// requires all files to be present in a crate's subtree.
+// eslint-disable-next-line @typescript-eslint/no-unused-vars
+import * as ts_ from "$asset$/typescript.d.ts";
+
+declare global {
+  namespace ts {
+    export = ts_;
+  }
+
+  namespace ts {
+    // this are marked @internal in TypeScript, but we need to access them,
+    // there is a risk these could change in future versions of TypeScript
+    export const libs: string[];
+    export const libMap: Map<string, string>;
+  }
+}
diff --git a/cli/js/compiler/type_directives.ts b/cli/js/compiler/type_directives.ts
new file mode 100644
index 000000000..0f4ce932c
--- /dev/null
+++ b/cli/js/compiler/type_directives.ts
@@ -0,0 +1,91 @@
+// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
+
+interface FileReference {
+  fileName: string;
+  pos: number;
+  end: number;
+}
+
+/** Remap the module name based on any supplied type directives passed. */
+export function getMappedModuleName(
+  source: FileReference,
+  typeDirectives: Map<FileReference, string>
+): string {
+  const { fileName: sourceFileName, pos: sourcePos } = source;
+  for (const [{ fileName, pos }, value] of typeDirectives.entries()) {
+    if (sourceFileName === fileName && sourcePos === pos) {
+      return value;
+    }
+  }
+  return source.fileName;
+}
+
+/** Matches directives that look something like this and parses out the value
+ * of the directive:
+ *
+ *      // @deno-types="./foo.d.ts"
+ *
+ * [See Diagram](http://bit.ly/31nZPCF)
+ */
+const typeDirectiveRegEx = /@deno-types\s*=\s*(["'])((?:(?=(\\?))\3.)*?)\1/gi;
+
+/** Matches `import`, `import from` or `export from` statements and parses out the value of the
+ * module specifier in the second capture group:
+ *
+ *      import "./foo.js"
+ *      import * as foo from "./foo.js"
+ *      export { a, b, c } from "./bar.js"
+ *
+ * [See Diagram](http://bit.ly/2lOsp0K)
+ */
+const importExportRegEx = /(?:import|export)(?:\s+|\s+[\s\S]*?from\s+)?(["'])((?:(?=(\\?))\3.)*?)\1/;
+
+/** Parses out any Deno type directives that are part of the source code, or
+ * returns `undefined` if there are not any.
+ */
+export function parseTypeDirectives(
+  sourceCode: string | undefined
+): Map<FileReference, string> | undefined {
+  if (!sourceCode) {
+    return;
+  }
+
+  // collect all the directives in the file and their start and end positions
+  const directives: FileReference[] = [];
+  let maybeMatch: RegExpExecArray | null = null;
+  while ((maybeMatch = typeDirectiveRegEx.exec(sourceCode))) {
+    const [matchString, , fileName] = maybeMatch;
+    const { index: pos } = maybeMatch;
+    directives.push({
+      fileName,
+      pos,
+      end: pos + matchString.length
+    });
+  }
+  if (!directives.length) {
+    return;
+  }
+
+  // work from the last directive backwards for the next `import`/`export`
+  // statement
+  directives.reverse();
+  const results = new Map<FileReference, string>();
+  for (const { end, fileName, pos } of directives) {
+    const searchString = sourceCode.substring(end);
+    const maybeMatch = importExportRegEx.exec(searchString);
+    if (maybeMatch) {
+      const [matchString, , targetFileName] = maybeMatch;
+      const targetPos =
+        end + maybeMatch.index + matchString.indexOf(targetFileName) - 1;
+      const target: FileReference = {
+        fileName: targetFileName,
+        pos: targetPos,
+        end: targetPos + targetFileName.length
+      };
+      results.set(target, fileName);
+    }
+    sourceCode = sourceCode.substring(0, pos);
+  }
+
+  return results;
+}
diff --git a/cli/js/compiler/util.ts b/cli/js/compiler/util.ts
new file mode 100644
index 000000000..c1afbd581
--- /dev/null
+++ b/cli/js/compiler/util.ts
@@ -0,0 +1,448 @@
+// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
+
+import { bold, cyan, yellow } from "../colors.ts";
+import { CompilerOptions } from "./api.ts";
+import { buildBundle } from "./bundler.ts";
+import { ConfigureResponse, Host } from "./host.ts";
+import { SourceFile } from "./sourcefile.ts";
+import { atob, TextEncoder } from "../web/text_encoding.ts";
+import * as compilerOps from "../ops/compiler.ts";
+import * as util from "../util.ts";
+import { assert } from "../util.ts";
+import { writeFileSync } from "../write_file.ts";
+
+/** Type for the write fall callback that allows delegation from the compiler
+ * host on writing files. */
+export type WriteFileCallback = (
+  fileName: string,
+  data: string,
+  sourceFiles?: readonly ts.SourceFile[]
+) => void;
+
+/** An object which is passed to `createWriteFile` to be used to read and set
+ * state related to the emit of a program. */
+export interface WriteFileState {
+  type: CompilerRequestType;
+  bundle?: boolean;
+  host?: Host;
+  outFile?: string;
+  rootNames: string[];
+  emitMap?: Record<string, string>;
+  emitBundle?: string;
+  sources?: Record<string, string>;
+}
+
+// Warning! The values in this enum are duplicated in `cli/msg.rs`
+// Update carefully!
+export enum CompilerRequestType {
+  Compile = 0,
+  RuntimeCompile = 1,
+  RuntimeTranspile = 2
+}
+
+export const OUT_DIR = "$deno$";
+
+/** Cache the contents of a file on the trusted side. */
+function cache(
+  moduleId: string,
+  emittedFileName: string,
+  contents: string,
+  checkJs = false
+): void {
+  util.log("compiler::cache", { moduleId, emittedFileName, checkJs });
+  const sf = SourceFile.get(moduleId);
+
+  if (sf) {
+    // NOTE: If it's a `.json` file we don't want to write it to disk.
+    // JSON files are loaded and used by TS compiler to check types, but we don't want
+    // to emit them to disk because output file is the same as input file.
+    if (sf.extension === ts.Extension.Json) {
+      return;
+    }
+
+    // NOTE: JavaScript files are only cached to disk if `checkJs`
+    // option in on
+    if (sf.extension === ts.Extension.Js && !checkJs) {
+      return;
+    }
+  }
+
+  if (emittedFileName.endsWith(".map")) {
+    // Source Map
+    compilerOps.cache(".map", moduleId, contents);
+  } else if (
+    emittedFileName.endsWith(".js") ||
+    emittedFileName.endsWith(".json")
+  ) {
+    // Compiled JavaScript
+    compilerOps.cache(".js", moduleId, contents);
+  } else {
+    assert(false, `Trying to cache unhandled file type "${emittedFileName}"`);
+  }
+}
+
+/** Retrieve an asset from Rust. */
+export function getAsset(name: string): string {
+  return compilerOps.getAsset(name);
+}
+
+/** Generates a `writeFile` function which can be passed to the compiler `Host`
+ * to use when emitting files. */
+export function createWriteFile(state: WriteFileState): WriteFileCallback {
+  const encoder = new TextEncoder();
+  if (state.type === CompilerRequestType.Compile) {
+    return function writeFile(
+      fileName: string,
+      data: string,
+      sourceFiles?: readonly ts.SourceFile[]
+    ): void {
+      assert(
+        sourceFiles != null,
+        `Unexpected emit of "${fileName}" which isn't part of a program.`
+      );
+      assert(state.host);
+      if (!state.bundle) {
+        assert(sourceFiles.length === 1);
+        cache(
+          sourceFiles[0].fileName,
+          fileName,
+          data,
+          state.host.getCompilationSettings().checkJs
+        );
+      } else {
+        // if the fileName is set to an internal value, just noop, this is
+        // used in the Rust unit tests.
+        if (state.outFile && state.outFile.startsWith(OUT_DIR)) {
+          return;
+        }
+        // we only support single root names for bundles
+        assert(
+          state.rootNames.length === 1,
+          `Only one root name supported.  Got "${JSON.stringify(
+            state.rootNames
+          )}"`
+        );
+        // this enriches the string with the loader and re-exports the
+        // exports of the root module
+        const content = buildBundle(state.rootNames[0], data, sourceFiles);
+        if (state.outFile) {
+          const encodedData = encoder.encode(content);
+          console.warn(`Emitting bundle to "${state.outFile}"`);
+          writeFileSync(state.outFile, encodedData);
+          console.warn(`${humanFileSize(encodedData.length)} emitted.`);
+        } else {
+          console.log(content);
+        }
+      }
+    };
+  }
+
+  return function writeFile(
+    fileName: string,
+    data: string,
+    sourceFiles?: readonly ts.SourceFile[]
+  ): void {
+    assert(sourceFiles != null);
+    assert(state.host);
+    assert(state.emitMap);
+    if (!state.bundle) {
+      assert(sourceFiles.length === 1);
+      state.emitMap[fileName] = data;
+      // we only want to cache the compiler output if we are resolving
+      // modules externally
+      if (!state.sources) {
+        cache(
+          sourceFiles[0].fileName,
+          fileName,
+          data,
+          state.host.getCompilationSettings().checkJs
+        );
+      }
+    } else {
+      // we only support single root names for bundles
+      assert(state.rootNames.length === 1);
+      state.emitBundle = buildBundle(state.rootNames[0], data, sourceFiles);
+    }
+  };
+}
+
+export interface ConvertCompilerOptionsResult {
+  files?: string[];
+  options: ts.CompilerOptions;
+}
+
+/** Take a runtime set of compiler options as stringified JSON and convert it
+ * to a set of TypeScript compiler options. */
+export function convertCompilerOptions(
+  str: string
+): ConvertCompilerOptionsResult {
+  const options: CompilerOptions = JSON.parse(str);
+  const out: Record<string, unknown> = {};
+  const keys = Object.keys(options) as Array<keyof CompilerOptions>;
+  const files: string[] = [];
+  for (const key of keys) {
+    switch (key) {
+      case "jsx":
+        const value = options[key];
+        if (value === "preserve") {
+          out[key] = ts.JsxEmit.Preserve;
+        } else if (value === "react") {
+          out[key] = ts.JsxEmit.React;
+        } else {
+          out[key] = ts.JsxEmit.ReactNative;
+        }
+        break;
+      case "module":
+        switch (options[key]) {
+          case "amd":
+            out[key] = ts.ModuleKind.AMD;
+            break;
+          case "commonjs":
+            out[key] = ts.ModuleKind.CommonJS;
+            break;
+          case "es2015":
+          case "es6":
+            out[key] = ts.ModuleKind.ES2015;
+            break;
+          case "esnext":
+            out[key] = ts.ModuleKind.ESNext;
+            break;
+          case "none":
+            out[key] = ts.ModuleKind.None;
+            break;
+          case "system":
+            out[key] = ts.ModuleKind.System;
+            break;
+          case "umd":
+            out[key] = ts.ModuleKind.UMD;
+            break;
+          default:
+            throw new TypeError("Unexpected module type");
+        }
+        break;
+      case "target":
+        switch (options[key]) {
+          case "es3":
+            out[key] = ts.ScriptTarget.ES3;
+            break;
+          case "es5":
+            out[key] = ts.ScriptTarget.ES5;
+            break;
+          case "es6":
+          case "es2015":
+            out[key] = ts.ScriptTarget.ES2015;
+            break;
+          case "es2016":
+            out[key] = ts.ScriptTarget.ES2016;
+            break;
+          case "es2017":
+            out[key] = ts.ScriptTarget.ES2017;
+            break;
+          case "es2018":
+            out[key] = ts.ScriptTarget.ES2018;
+            break;
+          case "es2019":
+            out[key] = ts.ScriptTarget.ES2019;
+            break;
+          case "es2020":
+            out[key] = ts.ScriptTarget.ES2020;
+            break;
+          case "esnext":
+            out[key] = ts.ScriptTarget.ESNext;
+            break;
+          default:
+            throw new TypeError("Unexpected emit target.");
+        }
+        break;
+      case "types":
+        const types = options[key];
+        assert(types);
+        files.push(...types);
+        break;
+      default:
+        out[key] = options[key];
+    }
+  }
+  return {
+    options: out as ts.CompilerOptions,
+    files: files.length ? files : undefined
+  };
+}
+
+/** An array of TypeScript diagnostic types we ignore. */
+export const ignoredDiagnostics = [
+  // TS2306: File 'file:///Users/rld/src/deno/cli/tests/subdir/amd_like.js' is
+  // not a module.
+  2306,
+  // TS1375: 'await' expressions are only allowed at the top level of a file
+  // when that file is a module, but this file has no imports or exports.
+  // Consider adding an empty 'export {}' to make this file a module.
+  1375,
+  // TS1103: 'for-await-of' statement is only allowed within an async function
+  // or async generator.
+  1103,
+  // TS2691: An import path cannot end with a '.ts' extension. Consider
+  // importing 'bad-module' instead.
+  2691,
+  // TS5009: Cannot find the common subdirectory path for the input files.
+  5009,
+  // TS5055: Cannot write file
+  // 'http://localhost:4545/cli/tests/subdir/mt_application_x_javascript.j4.js'
+  // because it would overwrite input file.
+  5055,
+  // TypeScript is overly opinionated that only CommonJS modules kinds can
+  // support JSON imports.  Allegedly this was fixed in
+  // Microsoft/TypeScript#26825 but that doesn't seem to be working here,
+  // so we will ignore complaints about this compiler setting.
+  5070,
+  // TS7016: Could not find a declaration file for module '...'. '...'
+  // implicitly has an 'any' type.  This is due to `allowJs` being off by
+  // default but importing of a JavaScript module.
+  7016
+];
+
+/** When doing a host configuration, processing the response and logging out
+ * and options which were ignored. */
+export function processConfigureResponse(
+  configResult: ConfigureResponse,
+  configPath: string
+): ts.Diagnostic[] | undefined {
+  const { ignoredOptions, diagnostics } = configResult;
+  if (ignoredOptions) {
+    console.warn(
+      yellow(`Unsupported compiler options in "${configPath}"\n`) +
+        cyan(`  The following options were ignored:\n`) +
+        `    ${ignoredOptions.map((value): string => bold(value)).join(", ")}`
+    );
+  }
+  return diagnostics;
+}
+
+// Constants used by `normalizeString` and `resolvePath`
+export const CHAR_DOT = 46; /* . */
+export const CHAR_FORWARD_SLASH = 47; /* / */
+
+/** Resolves `.` and `..` elements in a path with directory names */
+export function normalizeString(
+  path: string,
+  allowAboveRoot: boolean,
+  separator: string,
+  isPathSeparator: (code: number) => boolean
+): string {
+  let res = "";
+  let lastSegmentLength = 0;
+  let lastSlash = -1;
+  let dots = 0;
+  let code: number;
+  for (let i = 0, len = path.length; i <= len; ++i) {
+    if (i < len) code = path.charCodeAt(i);
+    else if (isPathSeparator(code!)) break;
+    else code = CHAR_FORWARD_SLASH;
+
+    if (isPathSeparator(code)) {
+      if (lastSlash === i - 1 || dots === 1) {
+        // NOOP
+      } else if (lastSlash !== i - 1 && dots === 2) {
+        if (
+          res.length < 2 ||
+          lastSegmentLength !== 2 ||
+          res.charCodeAt(res.length - 1) !== CHAR_DOT ||
+          res.charCodeAt(res.length - 2) !== CHAR_DOT
+        ) {
+          if (res.length > 2) {
+            const lastSlashIndex = res.lastIndexOf(separator);
+            if (lastSlashIndex === -1) {
+              res = "";
+              lastSegmentLength = 0;
+            } else {
+              res = res.slice(0, lastSlashIndex);
+              lastSegmentLength = res.length - 1 - res.lastIndexOf(separator);
+            }
+            lastSlash = i;
+            dots = 0;
+            continue;
+          } else if (res.length === 2 || res.length === 1) {
+            res = "";
+            lastSegmentLength = 0;
+            lastSlash = i;
+            dots = 0;
+            continue;
+          }
+        }
+        if (allowAboveRoot) {
+          if (res.length > 0) res += `${separator}..`;
+          else res = "..";
+          lastSegmentLength = 2;
+        }
+      } else {
+        if (res.length > 0) res += separator + path.slice(lastSlash + 1, i);
+        else res = path.slice(lastSlash + 1, i);
+        lastSegmentLength = i - lastSlash - 1;
+      }
+      lastSlash = i;
+      dots = 0;
+    } else if (code === CHAR_DOT && dots !== -1) {
+      ++dots;
+    } else {
+      dots = -1;
+    }
+  }
+  return res;
+}
+
+/** Return the common path shared by the `paths`.
+ *
+ * @param paths The set of paths to compare.
+ * @param sep An optional separator to use. Defaults to `/`.
+ * @internal
+ */
+export function commonPath(paths: string[], sep = "/"): string {
+  const [first = "", ...remaining] = paths;
+  if (first === "" || remaining.length === 0) {
+    return first.substring(0, first.lastIndexOf(sep) + 1);
+  }
+  const parts = first.split(sep);
+
+  let endOfPrefix = parts.length;
+  for (const path of remaining) {
+    const compare = path.split(sep);
+    for (let i = 0; i < endOfPrefix; i++) {
+      if (compare[i] !== parts[i]) {
+        endOfPrefix = i;
+      }
+    }
+
+    if (endOfPrefix === 0) {
+      return "";
+    }
+  }
+  const prefix = parts.slice(0, endOfPrefix).join(sep);
+  return prefix.endsWith(sep) ? prefix : `${prefix}${sep}`;
+}
+
+/** Utility function to turn the number of bytes into a human readable
+ * unit */
+function humanFileSize(bytes: number): string {
+  const thresh = 1000;
+  if (Math.abs(bytes) < thresh) {
+    return bytes + " B";
+  }
+  const units = ["kB", "MB", "GB", "TB", "PB", "EB", "ZB", "YB"];
+  let u = -1;
+  do {
+    bytes /= thresh;
+    ++u;
+  } while (Math.abs(bytes) >= thresh && u < units.length - 1);
+  return `${bytes.toFixed(1)} ${units[u]}`;
+}
+
+// @internal
+export function base64ToUint8Array(data: string): Uint8Array {
+  const binString = atob(data);
+  const size = binString.length;
+  const bytes = new Uint8Array(size);
+  for (let i = 0; i < size; i++) {
+    bytes[i] = binString.charCodeAt(i);
+  }
+  return bytes;
+}