18 files changed, 1154 insertions, 396 deletions

diff --git a/BUILD.gn b/BUILD.gn
index 38b194b9a..c7251981d 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -162,6 +162,7 @@ executable("snapshot_creator") {
 run_node("gen_declarations") {
   out_dir = target_gen_dir
   sources = [
+    "js/compiler.ts",
     "js/console.ts",
     "js/deno.ts",
     "js/globals.ts",
@@ -171,6 +172,7 @@ run_node("gen_declarations") {
     "js/util.ts",
   ]
   outputs = [
+    out_dir + "/js/compiler.d.ts",
     out_dir + "/js/console.d.ts",
     out_dir + "/js/deno.d.ts",
     out_dir + "/js/globals.d.ts",
@@ -196,6 +198,7 @@ run_node("bundle") {
   out_dir = "$target_gen_dir/bundle/"
   sources = [
     "js/assets.ts",
+    "js/compiler.ts",
     "js/console.ts",
     "js/fetch.ts",
     "js/fetch_types.d.ts",
@@ -204,7 +207,6 @@ run_node("bundle") {
     "js/main.ts",
     "js/os.ts",
     "js/plugins.d.ts",
-    "js/runtime.ts",
     "js/text_encoding.ts",
     "js/timers.ts",
     "js/types.d.ts",
diff --git a/js/assets.ts b/js/assets.ts
index 425ef3fc2..3b5691bc7 100644
--- a/js/assets.ts
+++ b/js/assets.ts
@@ -7,6 +7,7 @@
 // tslint:disable:max-line-length
 
 // Generated definitions
+import compilerDts from "gen/js/compiler.d.ts!string";
 import consoleDts from "gen/js/console.d.ts!string";
 import denoDts from "gen/js/deno.d.ts!string";
 import globalsDts from "gen/js/globals.d.ts!string";
@@ -55,6 +56,7 @@ import fetchTypesDts from "/js/fetch_types.d.ts!string";
 // prettier-ignore
 export const assetSourceCode: { [key: string]: string } = {
   // Generated definitions
+  "compiler.d.ts": compilerDts,
   "console.d.ts": consoleDts,
   "deno.d.ts": denoDts,
   "globals.d.ts": globalsDts,
diff --git a/js/compiler.ts b/js/compiler.ts
new file mode 100644
index 000000000..84330490f
--- /dev/null
+++ b/js/compiler.ts
@@ -0,0 +1,595 @@
+// Copyright 2018 the Deno authors. All rights reserved. MIT license.
+import * as ts from "typescript";
+import { assetSourceCode } from "./assets";
+import * as deno from "./deno";
+import { libdeno, window, globalEval } from "./globals";
+import * as os from "./os";
+import { RawSourceMap } from "./types";
+import { assert, log, notImplemented } from "./util";
+import * as sourceMaps from "./v8_source_maps";
+
+const EOL = "\n";
+const ASSETS = "$asset$";
+
+// tslint:disable:no-any
+type AmdCallback = (...args: any[]) => void;
+type AmdErrback = (err: any) => void;
+export type AmdFactory = (...args: any[]) => object | void;
+// tslint:enable:no-any
+export type AmdDefine = (deps: string[], factory: AmdFactory) => void;
+type AmdRequire = (
+  deps: string[],
+  callback: AmdCallback,
+  errback?: AmdErrback
+) => void;
+
+// The location that a module is being loaded from. This could be a directory,
+// like ".", or it could be a module specifier like
+// "http://gist.github.com/somefile.ts"
+type ContainingFile = string;
+// The internal local filename of a compiled module. It will often be something
+// like "/home/ry/.deno/gen/f7b4605dfbc4d3bb356e98fda6ceb1481e4a8df5.js"
+type ModuleFileName = string;
+// The external name of a module - could be a URL or could be a relative path.
+// Examples "http://gist.github.com/somefile.ts" or "./somefile.ts"
+type ModuleSpecifier = string;
+// The compiled source code which is cached in .deno/gen/
+type OutputCode = string;
+
+/**
+ * Abstraction of the APIs required from the `os` module so they can be
+ * easily mocked.
+ */
+export interface Os {
+  codeCache: typeof os.codeCache;
+  codeFetch: typeof os.codeFetch;
+  exit: typeof os.exit;
+}
+
+/**
+ * Abstraction of the APIs required from the `typescript` module so they can
+ * be easily mocked.
+ */
+export interface Ts {
+  createLanguageService: typeof ts.createLanguageService;
+  /* tslint:disable-next-line:max-line-length */
+  formatDiagnosticsWithColorAndContext: typeof ts.formatDiagnosticsWithColorAndContext;
+}
+
+/**
+ * A simple object structure for caching resolved modules and their contents.
+ *
+ * Named `ModuleMetaData` to clarify it is just a representation of meta data of
+ * the module, not the actual module instance.
+ */
+export class ModuleMetaData {
+  public readonly exports = {};
+  public scriptSnapshot?: ts.IScriptSnapshot;
+  public scriptVersion = "";
+
+  constructor(
+    public readonly fileName: string,
+    public readonly sourceCode = "",
+    public outputCode = ""
+  ) {
+    if (outputCode !== "" || fileName.endsWith(".d.ts")) {
+      this.scriptVersion = "1";
+    }
+  }
+}
+
+/**
+ * The required minimal API to allow formatting of TypeScript compiler
+ * diagnostics.
+ */
+const formatDiagnosticsHost: ts.FormatDiagnosticsHost = {
+  getCurrentDirectory: () => ".",
+  getCanonicalFileName: (fileName: string) => fileName,
+  getNewLine: () => EOL
+};
+
+/**
+ * Throw a module resolution error, when a module is unsuccessfully resolved.
+ */
+function throwResolutionError(
+  message: string,
+  moduleSpecifier: ModuleSpecifier,
+  containingFile: ContainingFile
+): never {
+  throw new Error(
+    // tslint:disable-next-line:max-line-length
+    `Cannot resolve module "${moduleSpecifier}" from "${containingFile}".\n  ${message}`
+  );
+}
+
+// ts.ScriptKind is not available at runtime, so local enum definition
+enum ScriptKind {
+  JS = 1,
+  TS = 3,
+  JSON = 6
+}
+
+/**
+ * A singleton class that combines the TypeScript Language Service host API
+ * with Deno specific APIs to provide an interface for compiling and running
+ * TypeScript and JavaScript modules.
+ */
+export class DenoCompiler implements ts.LanguageServiceHost {
+  // Modules are usually referenced by their ModuleSpecifier and ContainingFile,
+  // and keeping a map of the resolved module file name allows more efficient
+  // future resolution
+  private readonly _fileNamesMap = new Map<
+    ContainingFile,
+    Map<ModuleSpecifier, ModuleFileName>
+  >();
+  // A reference to global eval, so it can be monkey patched during testing
+  private _globalEval = globalEval;
+  // A reference to the log utility, so it can be monkey patched during testing
+  private _log = log;
+  // A map of module file names to module meta data
+  private readonly _moduleMetaDataMap = new Map<
+    ModuleFileName,
+    ModuleMetaData
+  >();
+  // TODO ideally this are not static and can be influenced by command line
+  // arguments
+  private readonly _options: Readonly<ts.CompilerOptions> = {
+    allowJs: true,
+    module: ts.ModuleKind.AMD,
+    outDir: "$deno$",
+    // TODO https://github.com/denoland/deno/issues/23
+    inlineSourceMap: true,
+    inlineSources: true,
+    stripComments: true,
+    target: ts.ScriptTarget.ESNext
+  };
+  // A reference to the `./os.ts` module, so it can be monkey patched during
+  // testing
+  private _os: Os = os;
+  // Used to contain the script file we are currently running
+  private _scriptFileNames: string[] = [];
+  // A reference to the TypeScript LanguageService instance so it can be
+  // monkey patched during testing
+  private _service: ts.LanguageService;
+  // A reference to `typescript` module so it can be monkey patched during
+  // testing
+  private _ts: Ts = ts;
+  // A reference to the global scope so it can be monkey patched during
+  // testing
+  private _window = window;
+
+  /**
+   * The TypeScript language service often refers to the resolved fileName of
+   * a module, this is a shortcut to avoid unnecessary module resolution logic
+   * for modules that may have been initially resolved by a `moduleSpecifier`
+   * and `containingFile`.  Also, `resolveModule()` throws when the module
+   * cannot be resolved, which isn't always valid when dealing with the
+   * TypeScript compiler, but the TypeScript compiler shouldn't be asking about
+   * external modules that we haven't told it about yet.
+   */
+  private _getModuleMetaData(
+    fileName: ModuleFileName
+  ): ModuleMetaData | undefined {
+    return this._moduleMetaDataMap.has(fileName)
+      ? this._moduleMetaDataMap.get(fileName)
+      : fileName.startsWith(ASSETS)
+        ? this.resolveModule(fileName, "")
+        : undefined;
+  }
+
+  /**
+   * Setup being able to map back source references back to their source
+   *
+   * TODO is this the best place for this?  It is tightly coupled to how the
+   * compiler works, but it is also tightly coupled to how the whole runtime
+   * environment is bootstrapped.  It also needs efficient access to the
+   * `outputCode` of the module information, which exists inside of the
+   * compiler instance.
+   */
+  private _setupSourceMaps(): void {
+    sourceMaps.install({
+      installPrepareStackTrace: true,
+      getGeneratedContents: (fileName: string): string | RawSourceMap => {
+        this._log("getGeneratedContents", fileName);
+        if (fileName === "gen/bundle/main.js") {
+          assert(libdeno.mainSource.length > 0);
+          return libdeno.mainSource;
+        } else if (fileName === "main.js.map") {
+          return libdeno.mainSourceMap;
+        } else if (fileName === "deno_main.js") {
+          return "";
+        } else {
+          const moduleMetaData = this._moduleMetaDataMap.get(fileName);
+          if (!moduleMetaData) {
+            this._log("getGeneratedContents cannot find", fileName);
+            return "";
+          }
+          return moduleMetaData.outputCode;
+        }
+      }
+    });
+  }
+
+  private constructor() {
+    if (DenoCompiler._instance) {
+      throw new TypeError("Attempt to create an additional compiler.");
+    }
+    this._service = this._ts.createLanguageService(this);
+    this._setupSourceMaps();
+  }
+
+  // Deno specific compiler API
+
+  /**
+   * Retrieve the output of the TypeScript compiler for a given `fileName`.
+   */
+  compile(fileName: ModuleFileName): OutputCode {
+    const service = this._service;
+    const output = service.getEmitOutput(fileName);
+
+    // Get the relevant diagnostics - this is 3x faster than
+    // `getPreEmitDiagnostics`.
+    const diagnostics = [
+      ...service.getCompilerOptionsDiagnostics(),
+      ...service.getSyntacticDiagnostics(fileName),
+      ...service.getSemanticDiagnostics(fileName)
+    ];
+    if (diagnostics.length > 0) {
+      const errMsg = this._ts.formatDiagnosticsWithColorAndContext(
+        diagnostics,
+        formatDiagnosticsHost
+      );
+      console.log(errMsg);
+      // All TypeScript errors are terminal for deno
+      this._os.exit(1);
+    }
+
+    assert(!output.emitSkipped, "The emit was skipped for an unknown reason.");
+
+    // Currently we are inlining source maps, there should be only 1 output file
+    // See: https://github.com/denoland/deno/issues/23
+    assert(
+      output.outputFiles.length === 1,
+      "Only single file should be output."
+    );
+
+    const [outputFile] = output.outputFiles;
+    return outputFile.text;
+  }
+
+  /**
+   * Create a localized AMD `define` function and return it.
+   */
+  makeDefine(moduleMetaData: ModuleMetaData): AmdDefine {
+    const localDefine = (deps: string[], factory: AmdFactory): void => {
+      // TypeScript will emit a local require dependency when doing dynamic
+      // `import()`
+      const localRequire: AmdRequire = (
+        deps: string[],
+        callback: AmdCallback,
+        errback?: AmdErrback
+      ): void => {
+        this._log("localRequire", deps);
+        try {
+          const args = deps.map(dep => {
+            if (dep in DenoCompiler._builtins) {
+              return DenoCompiler._builtins[dep];
+            } else {
+              const depModuleMetaData = this.run(dep, moduleMetaData.fileName);
+              return depModuleMetaData.exports;
+            }
+          });
+          callback(...args);
+        } catch (e) {
+          if (errback) {
+            errback(e);
+          } else {
+            throw e;
+          }
+        }
+      };
+      const localExports = moduleMetaData.exports;
+      this._log("localDefine", moduleMetaData.fileName, deps, localExports);
+      const args = deps.map(dep => {
+        if (dep === "require") {
+          return localRequire;
+        } else if (dep === "exports") {
+          return localExports;
+        } else if (dep in DenoCompiler._builtins) {
+          return DenoCompiler._builtins[dep];
+        } else {
+          const depModuleMetaData = this.run(dep, moduleMetaData.fileName);
+          return depModuleMetaData.exports;
+        }
+      });
+      factory(...args);
+    };
+    return localDefine;
+  }
+
+  /**
+   * Given a `moduleSpecifier` and `containingFile` retrieve the cached
+   * `fileName` for a given module.  If the module has yet to be resolved
+   * this will return `undefined`.
+   */
+  resolveFileName(
+    moduleSpecifier: ModuleSpecifier,
+    containingFile: ContainingFile
+  ): ModuleFileName | undefined {
+    this._log("resolveFileName", { moduleSpecifier, containingFile });
+    const innerMap = this._fileNamesMap.get(containingFile);
+    if (innerMap) {
+      return innerMap.get(moduleSpecifier);
+    }
+    return undefined;
+  }
+
+  /**
+   * Given a `moduleSpecifier` and `containingFile`, resolve the module and
+   * return the `ModuleMetaData`.
+   */
+  resolveModule(
+    moduleSpecifier: ModuleSpecifier,
+    containingFile: ContainingFile
+  ): ModuleMetaData {
+    this._log("resolveModule", { moduleSpecifier, containingFile });
+    assert(moduleSpecifier != null && moduleSpecifier.length > 0);
+    let fileName = this.resolveFileName(moduleSpecifier, containingFile);
+    if (fileName && this._moduleMetaDataMap.has(fileName)) {
+      return this._moduleMetaDataMap.get(fileName)!;
+    }
+    let sourceCode: string | undefined;
+    let outputCode: string | undefined;
+    if (
+      moduleSpecifier.startsWith(ASSETS) ||
+      containingFile.startsWith(ASSETS)
+    ) {
+      // Assets are compiled into the runtime javascript bundle.
+      // we _know_ `.pop()` will return a string, but TypeScript doesn't so
+      // not null assertion
+      const moduleId = moduleSpecifier.split("/").pop()!;
+      const assetName = moduleId.includes(".") ? moduleId : `${moduleId}.d.ts`;
+      assert(assetName in assetSourceCode, `No such asset "${assetName}"`);
+      sourceCode = assetSourceCode[assetName];
+      fileName = `${ASSETS}/${assetName}`;
+    } else {
+      // We query Rust with a CodeFetch message. It will load the sourceCode,
+      // and if there is any outputCode cached, will return that as well.
+      let fetchResponse;
+      try {
+        fetchResponse = this._os.codeFetch(moduleSpecifier, containingFile);
+      } catch (e) {
+        return throwResolutionError(
+          `os.codeFetch message: ${e.message}`,
+          moduleSpecifier,
+          containingFile
+        );
+      }
+      fileName = fetchResponse.filename || undefined;
+      sourceCode = fetchResponse.sourceCode || undefined;
+      outputCode = fetchResponse.outputCode || undefined;
+    }
+    if (!sourceCode || sourceCode.length === 0 || !fileName) {
+      return throwResolutionError(
+        "Invalid source code or file name.",
+        moduleSpecifier,
+        containingFile
+      );
+    }
+    this._log("resolveModule sourceCode length ", sourceCode.length);
+    this.setFileName(moduleSpecifier, containingFile, fileName);
+    if (fileName && this._moduleMetaDataMap.has(fileName)) {
+      return this._moduleMetaDataMap.get(fileName)!;
+    }
+    const moduleMetaData = new ModuleMetaData(fileName, sourceCode, outputCode);
+    this._moduleMetaDataMap.set(fileName, moduleMetaData);
+    return moduleMetaData;
+  }
+
+  /**
+   * Resolve the `fileName` for a given `moduleSpecifier` and `containingFile`
+   */
+  resolveModuleName(
+    moduleSpecifier: ModuleSpecifier,
+    containingFile: ContainingFile
+  ): ModuleFileName | undefined {
+    const moduleMetaData = this.resolveModule(moduleSpecifier, containingFile);
+    return moduleMetaData ? moduleMetaData.fileName : undefined;
+  }
+
+  /* tslint:disable-next-line:no-any */
+  /**
+   * Execute a module based on the `moduleSpecifier` and the `containingFile`
+   * and return the resulting `FileModule`.
+   */
+  run(
+    moduleSpecifier: ModuleSpecifier,
+    containingFile: ContainingFile
+  ): ModuleMetaData {
+    this._log("run", { moduleSpecifier, containingFile });
+    const moduleMetaData = this.resolveModule(moduleSpecifier, containingFile);
+    const fileName = moduleMetaData.fileName;
+    this._scriptFileNames = [fileName];
+    const sourceCode = moduleMetaData.sourceCode;
+    let outputCode = moduleMetaData.outputCode;
+    if (!outputCode) {
+      outputCode = moduleMetaData.outputCode = `${this.compile(
+        fileName
+      )}\n//# sourceURL=${fileName}`;
+      moduleMetaData!.scriptVersion = "1";
+      this._os.codeCache(fileName, sourceCode, outputCode);
+    }
+    this._window.define = this.makeDefine(moduleMetaData);
+    this._globalEval(moduleMetaData.outputCode);
+    this._window.define = undefined;
+    return moduleMetaData!;
+  }
+
+  /**
+   * Caches the resolved `fileName` in relationship to the `moduleSpecifier`
+   * and `containingFile` in order to reduce calls to the privileged side
+   * to retrieve the contents of a module.
+   */
+  setFileName(
+    moduleSpecifier: ModuleSpecifier,
+    containingFile: ContainingFile,
+    fileName: ModuleFileName
+  ): void {
+    this._log("setFileName", { moduleSpecifier, containingFile });
+    let innerMap = this._fileNamesMap.get(containingFile);
+    if (!innerMap) {
+      innerMap = new Map();
+      this._fileNamesMap.set(containingFile, innerMap);
+    }
+    innerMap.set(moduleSpecifier, fileName);
+  }
+
+  // TypeScript Language Service API
+
+  getCompilationSettings(): ts.CompilerOptions {
+    this._log("getCompilationSettings()");
+    return this._options;
+  }
+
+  getNewLine(): string {
+    return EOL;
+  }
+
+  getScriptFileNames(): string[] {
+    // This is equal to `"files"` in the `tsconfig.json`, therefore we only need
+    // to include the actual base source files we are evaluating at the moment,
+    // which would be what is set during the `.run()`
+    return this._scriptFileNames;
+  }
+
+  getScriptKind(fileName: ModuleFileName): ts.ScriptKind {
+    this._log("getScriptKind()", fileName);
+    const suffix = fileName.substr(fileName.lastIndexOf(".") + 1);
+    switch (suffix) {
+      case "ts":
+        return ScriptKind.TS;
+      case "js":
+        return ScriptKind.JS;
+      case "json":
+        return ScriptKind.JSON;
+      default:
+        return this._options.allowJs ? ScriptKind.JS : ScriptKind.TS;
+    }
+  }
+
+  getScriptVersion(fileName: ModuleFileName): string {
+    this._log("getScriptVersion()", fileName);
+    const moduleMetaData = this._getModuleMetaData(fileName);
+    return (moduleMetaData && moduleMetaData.scriptVersion) || "";
+  }
+
+  getScriptSnapshot(fileName: ModuleFileName): ts.IScriptSnapshot | undefined {
+    this._log("getScriptSnapshot()", fileName);
+    const moduleMetaData = this._getModuleMetaData(fileName);
+    if (moduleMetaData) {
+      return (
+        moduleMetaData.scriptSnapshot ||
+        (moduleMetaData.scriptSnapshot = {
+          getText(start, end) {
+            return moduleMetaData.sourceCode.substring(start, end);
+          },
+          getLength() {
+            return moduleMetaData.sourceCode.length;
+          },
+          getChangeRange() {
+            return undefined;
+          }
+        })
+      );
+    } else {
+      return undefined;
+    }
+  }
+
+  getCurrentDirectory(): string {
+    this._log("getCurrentDirectory()");
+    return "";
+  }
+
+  getDefaultLibFileName(): string {
+    this._log("getDefaultLibFileName()");
+    const moduleSpecifier = "lib.globals.d.ts";
+    const moduleMetaData = this.resolveModule(moduleSpecifier, ASSETS);
+    return moduleMetaData.fileName;
+  }
+
+  useCaseSensitiveFileNames(): boolean {
+    this._log("useCaseSensitiveFileNames");
+    return true;
+  }
+
+  readFile(path: string): string | undefined {
+    this._log("readFile", path);
+    return notImplemented();
+  }
+
+  fileExists(fileName: string): boolean {
+    const moduleMetaData = this._getModuleMetaData(fileName);
+    const exists = moduleMetaData != null;
+    this._log("fileExists", fileName, exists);
+    return exists;
+  }
+
+  resolveModuleNames(
+    moduleNames: ModuleSpecifier[],
+    containingFile: ContainingFile
+  ): ts.ResolvedModule[] {
+    this._log("resolveModuleNames", { moduleNames, containingFile });
+    return moduleNames.map(name => {
+      let resolvedFileName;
+      if (name === "deno") {
+        resolvedFileName = this.resolveModuleName("deno.d.ts", ASSETS);
+      } else if (name === "compiler") {
+        resolvedFileName = this.resolveModuleName("compiler.d.ts", ASSETS);
+      } else if (name === "typescript") {
+        resolvedFileName = this.resolveModuleName("typescript.d.ts", ASSETS);
+      } else {
+        resolvedFileName = this.resolveModuleName(name, containingFile);
+      }
+      // According to the interface we shouldn't return `undefined` but if we
+      // fail to return the same length of modules to those we cannot resolve
+      // then TypeScript fails on an assertion that the lengths can't be
+      // different, so we have to return an "empty" resolved module
+      // TODO: all this does is push the problem downstream, and TypeScript
+      // will complain it can't identify the type of the file and throw
+      // a runtime exception, so we need to handle missing modules better
+      resolvedFileName = resolvedFileName || "";
+      // This flags to the compiler to not go looking to transpile functional
+      // code, anything that is in `/$asset$/` is just library code
+      const isExternalLibraryImport = resolvedFileName.startsWith(ASSETS);
+      // TODO: we should be returning a ts.ResolveModuleFull
+      return { resolvedFileName, isExternalLibraryImport };
+    });
+  }
+
+  // Deno specific static properties and methods
+
+  /**
+   * Built in modules which can be returned to external modules
+   *
+   * Placed as a private static otherwise we get use before
+   * declared with the `DenoCompiler`
+   */
+  // tslint:disable-next-line:no-any
+  private static _builtins: { [mid: string]: any } = {
+    typescript: ts,
+    deno,
+    compiler: { DenoCompiler, ModuleMetaData }
+  };
+
+  private static _instance: DenoCompiler | undefined;
+
+  /**
+   * Returns the instance of `DenoCompiler` or creates a new instance.
+   */
+  static instance(): DenoCompiler {
+    return (
+      DenoCompiler._instance || (DenoCompiler._instance = new DenoCompiler())
+    );
+  }
+}
diff --git a/js/compiler_test.ts b/js/compiler_test.ts
new file mode 100644
index 000000000..d8861e2a9
--- /dev/null
+++ b/js/compiler_test.ts
@@ -0,0 +1,471 @@
+// Copyright 2018 the Deno authors. All rights reserved. MIT license.
+import { test, assert, assertEqual } from "./testing/testing.ts";
+import * as compiler from "compiler";
+import * as ts from "typescript";
+
+// We use a silly amount of `any` in these tests...
+// tslint:disable:no-any
+
+const { DenoCompiler, ModuleMetaData } = compiler;
+
+// Enums like this don't exist at runtime, so local copy
+enum ScriptKind {
+  JS = 1,
+  TS = 3,
+  JSON = 6
+}
+
+interface ModuleInfo {
+  moduleName: string | null;
+  filename: string | null;
+  sourceCode: string | null;
+  outputCode: string | null;
+}
+
+const compilerInstance = DenoCompiler.instance();
+
+// References to orignal items we are going to mock
+const originals = {
+  _globalEval: (compilerInstance as any)._globalEval,
+  _log: (compilerInstance as any)._log,
+  _os: (compilerInstance as any)._os,
+  _ts: (compilerInstance as any)._ts,
+  _service: (compilerInstance as any)._service,
+  _window: (compilerInstance as any)._window
+};
+
+function mockModuleInfo(
+  moduleName: string | null,
+  filename: string | null,
+  sourceCode: string | null,
+  outputCode: string | null
+): ModuleInfo {
+  return {
+    moduleName,
+    filename,
+    sourceCode,
+    outputCode
+  };
+}
+
+// Some fixtures we will us in testing
+const fooBarTsSource = `import * as compiler from "compiler";
+console.log(compiler);
+export const foo = "bar";
+`;
+
+const fooBazTsSource = `import { foo } from "./bar.ts";
+console.log(foo);
+`;
+
+// TODO(#23) Remove source map strings from fooBarTsOutput.
+// tslint:disable:max-line-length
+const fooBarTsOutput = `define(["require", "exports", "compiler"], function (require, exports, compiler) {
+    "use strict";
+    Object.defineProperty(exports, "__esModule", { value: true });
+    console.log(compiler);
+    exports.foo = "bar";
+});
+//# sourceMappingURL=data:application/json;base64,eyJ2ZXJzaW9uIjozLCJmaWxlIjoiYmFyLmpzIiwic291cmNlUm9vdCI6IiIsInNvdXJjZXMiOlsiZmlsZTovLy9yb290L3Byb2plY3QvZm9vL2Jhci50cyJdLCJuYW1lcyI6W10sIm1hcHBpbmdzIjoiOzs7SUFDQSxPQUFPLENBQUMsR0FBRyxDQUFDLFFBQVEsQ0FBQyxDQUFDO0lBQ1QsUUFBQSxHQUFHLEdBQUcsS0FBSyxDQUFDIiwic291cmNlc0NvbnRlbnQiOlsiaW1wb3J0ICogYXMgY29tcGlsZXIgZnJvbSBcImNvbXBpbGVyXCI7XG5jb25zb2xlLmxvZyhjb21waWxlcik7XG5leHBvcnQgY29uc3QgZm9vID0gXCJiYXJcIjtcbiJdfQ==
+//# sourceURL=/root/project/foo/bar.ts`;
+
+// TODO(#23) Remove source map strings from fooBazTsOutput.
+const fooBazTsOutput = `define(["require", "exports", "./bar.ts"], function (require, exports, bar_ts_1) {
+  "use strict";
+  Object.defineProperty(exports, "__esModule", { value: true });
+  console.log(bar_ts_1.foo);
+});
+//# sourceMappingURL=data:application/json;base64,eyJ2ZXJzaW9uIjozLCJmaWxlIjoiYmF6LmpzIiwic291cmNlUm9vdCI6IiIsInNvdXJjZXMiOlsiZmlsZTovLy9yb290L3Byb2plY3QvZm9vL2Jhei50cyJdLCJuYW1lcyI6W10sIm1hcHBpbmdzIjoiOzs7SUFDQSxPQUFPLENBQUMsR0FBRyxDQUFDLFlBQUcsQ0FBQyxDQUFDIiwic291cmNlc0NvbnRlbnQiOlsiaW1wb3J0IHsgZm9vIH0gZnJvbSBcIi4vYmFyLnRzXCI7XG5jb25zb2xlLmxvZyhmb28pO1xuIl19
+//# sourceURL=/root/project/foo/baz.ts`;
+// tslint:enable:max-line-length
+
+const moduleMap: {
+  [containFile: string]: { [moduleSpecifier: string]: ModuleInfo };
+} = {
+  "/root/project": {
+    "foo/bar.ts": mockModuleInfo(
+      "foo/bar",
+      "/root/project/foo/bar.ts",
+      fooBarTsSource,
+      null
+    ),
+    "foo/baz.ts": mockModuleInfo(
+      "foo/baz",
+      "/root/project/foo/baz.ts",
+      fooBazTsSource,
+      null
+    ),
+    "foo/qat.ts": mockModuleInfo(
+      "foo/qat",
+      "/root/project/foo/qat.ts",
+      null,
+      null
+    )
+  },
+  "/root/project/foo/baz.ts": {
+    "./bar.ts": mockModuleInfo(
+      "foo/bar",
+      "/root/project/foo/bar.ts",
+      fooBarTsSource,
+      fooBarTsOutput
+    )
+  }
+};
+
+const emittedFiles = {
+  "/root/project/foo/qat.ts": "console.log('foo');"
+};
+
+let globalEvalStack: string[] = [];
+let getEmitOutputStack: string[] = [];
+let logStack: any[][] = [];
+let codeCacheStack: Array<{
+  fileName: string;
+  sourceCode: string;
+  outputCode: string;
+}> = [];
+let codeFetchStack: Array<{
+  moduleSpecifier: string;
+  containingFile: string;
+}> = [];
+
+function reset() {
+  codeFetchStack = [];
+  codeCacheStack = [];
+  logStack = [];
+  getEmitOutputStack = [];
+  globalEvalStack = [];
+}
+
+let mockDeps: string[] | undefined;
+let mockFactory: compiler.AmdFactory;
+
+function globalEvalMock(x: string): void {
+  globalEvalStack.push(x);
+  if (windowMock.define && mockDeps && mockFactory) {
+    windowMock.define(mockDeps, mockFactory);
+  }
+}
+function logMock(...args: any[]): void {
+  logStack.push(args);
+}
+const osMock: compiler.Os = {
+  codeCache(fileName: string, sourceCode: string, outputCode: string): void {
+    codeCacheStack.push({ fileName, sourceCode, outputCode });
+  },
+  codeFetch(moduleSpecifier: string, containingFile: string): ModuleInfo {
+    codeFetchStack.push({ moduleSpecifier, containingFile });
+    if (containingFile in moduleMap) {
+      if (moduleSpecifier in moduleMap[containingFile]) {
+        return moduleMap[containingFile][moduleSpecifier];
+      }
+    }
+    return mockModuleInfo(null, null, null, null);
+  },
+  exit(code: number): never {
+    throw new Error(`os.exit(${code})`);
+  }
+};
+const tsMock: compiler.Ts = {
+  createLanguageService(host: ts.LanguageServiceHost): ts.LanguageService {
+    return {} as ts.LanguageService;
+  },
+  formatDiagnosticsWithColorAndContext(
+    diagnostics: ReadonlyArray<ts.Diagnostic>,
+    host: ts.FormatDiagnosticsHost
+  ): string {
+    return "";
+  }
+};
+
+const getEmitOutputPassThrough = true;
+
+const serviceMock = {
+  getCompilerOptionsDiagnostics(): ts.Diagnostic[] {
+    return originals._service.getCompilerOptionsDiagnostics.call(
+      originals._service
+    );
+  },
+  getEmitOutput(fileName: string): ts.EmitOutput {
+    getEmitOutputStack.push(fileName);
+    if (getEmitOutputPassThrough) {
+      return originals._service.getEmitOutput.call(
+        originals._service,
+        fileName
+      );
+    }
+    if (fileName in emittedFiles) {
+      return {
+        outputFiles: [{ text: emittedFiles[fileName] }] as any,
+        emitSkipped: false
+      };
+    }
+    return { outputFiles: [], emitSkipped: false };
+  },
+  getSemanticDiagnostics(fileName: string): ts.Diagnostic[] {
+    return originals._service.getSemanticDiagnostics.call(
+      originals._service,
+      fileName
+    );
+  },
+  getSyntacticDiagnostics(fileName: string): ts.Diagnostic[] {
+    return originals._service.getSyntacticDiagnostics.call(
+      originals._service,
+      fileName
+    );
+  }
+};
+const windowMock: { define?: compiler.AmdDefine } = {};
+const mocks = {
+  _globalEval: globalEvalMock,
+  _log: logMock,
+  _os: osMock,
+  _ts: tsMock,
+  _service: serviceMock,
+  _window: windowMock
+};
+
+// Setup the mocks
+test(function compilerTestsSetup() {
+  assert("_globalEval" in compilerInstance);
+  assert("_log" in compilerInstance);
+  assert("_os" in compilerInstance);
+  assert("_ts" in compilerInstance);
+  assert("_service" in compilerInstance);
+  assert("_window" in compilerInstance);
+  Object.assign(compilerInstance, mocks);
+});
+
+test(function compilerInstance() {
+  assert(DenoCompiler != null);
+  assert(DenoCompiler.instance() != null);
+});
+
+// Testing the internal APIs
+
+test(function compilerMakeDefine() {
+  const moduleMetaData = new ModuleMetaData(
+    "/root/project/foo/bar.ts",
+    fooBarTsSource,
+    fooBarTsOutput
+  );
+  const localDefine = compilerInstance.makeDefine(moduleMetaData);
+  let factoryCalled = false;
+  localDefine(
+    ["require", "exports", "compiler"],
+    (_require, _exports, _compiler): void => {
+      factoryCalled = true;
+      assertEqual(
+        typeof _require,
+        "function",
+        "localRequire should be a function"
+      );
+      assert(_exports != null);
+      assert(
+        Object.keys(_exports).length === 0,
+        "exports should have no properties"
+      );
+      assert(compiler === _compiler, "compiler should be passed to factory");
+    }
+  );
+  assert(factoryCalled, "Factory expected to be called");
+});
+
+// TODO testMakeDefineExternalModule - testing that make define properly runs
+// external modules, this is implicitly tested though in
+// `compilerRunMultiModule`
+
+test(function compilerRun() {
+  // equal to `deno foo/bar.ts`
+  reset();
+  const result = compilerInstance.run("foo/bar.ts", "/root/project");
+  assert(result instanceof ModuleMetaData);
+  assertEqual(codeFetchStack.length, 1);
+  assertEqual(codeCacheStack.length, 1);
+  assertEqual(globalEvalStack.length, 1);
+
+  const lastGlobalEval = globalEvalStack.pop();
+  assertEqual(lastGlobalEval, fooBarTsOutput);
+  const lastCodeFetch = codeFetchStack.pop();
+  assertEqual(lastCodeFetch, {
+    moduleSpecifier: "foo/bar.ts",
+    containingFile: "/root/project"
+  });
+  const lastCodeCache = codeCacheStack.pop();
+  assertEqual(lastCodeCache, {
+    fileName: "/root/project/foo/bar.ts",
+    sourceCode: fooBarTsSource,
+    outputCode: fooBarTsOutput
+  });
+});
+
+test(function compilerRunMultiModule() {
+  // equal to `deno foo/baz.ts`
+  reset();
+  let factoryRun = false;
+  mockDeps = ["require", "exports", "compiler"];
+  mockFactory = (...deps: any[]) => {
+    const [_require, _exports, _compiler] = deps;
+    assertEqual(typeof _require, "function");
+    assertEqual(typeof _exports, "object");
+    assertEqual(_compiler, compiler);
+    factoryRun = true;
+    Object.defineProperty(_exports, "__esModule", { value: true });
+    _exports.foo = "bar";
+    // it is too complicated to test the outer factory, because the localised
+    // make define already has a reference to this factory and it can't really
+    // be easily unwound.  So we will do what we can with the inner one and
+    // then just clear it...
+    mockDeps = undefined;
+    mockFactory = undefined;
+  };
+
+  const result = compilerInstance.run("foo/baz.ts", "/root/project");
+  assert(result instanceof ModuleMetaData);
+  // we have mocked that foo/bar.ts is already cached, so two fetches,
+  // but only a single cache
+  assertEqual(codeFetchStack.length, 2);
+  assertEqual(codeCacheStack.length, 1);
+  // because of the challenges with the way the module factories are generated
+  // we only get one invocation of the `globalEval` mock.
+  assertEqual(globalEvalStack.length, 1);
+  assert(factoryRun);
+});
+
+// TypeScript LanguageServiceHost APIs
+
+test(function compilerGetCompilationSettings() {
+  const result = compilerInstance.getCompilationSettings();
+  for (const key of [
+    "allowJs",
+    "module",
+    "outDir",
+    "inlineSourceMap",
+    "inlineSources",
+    "stripComments",
+    "target"
+  ]) {
+    assert(key in result, `Expected "${key}" in compiler options.`);
+  }
+});
+
+test(function compilerGetNewLine() {
+  const result = compilerInstance.getNewLine();
+  assertEqual(result, "\n", "Expected newline value of '\\n'.");
+});
+
+test(function compilerGetScriptFileNames() {
+  compilerInstance.run("foo/bar.ts", "/root/project");
+  const result = compilerInstance.getScriptFileNames();
+  assertEqual(result.length, 1, "Expected only a single filename.");
+  assertEqual(result[0], "/root/project/foo/bar.ts");
+});
+
+test(function compilerGetScriptKind() {
+  assertEqual(compilerInstance.getScriptKind("foo.ts"), ScriptKind.TS);
+  assertEqual(compilerInstance.getScriptKind("foo.d.ts"), ScriptKind.TS);
+  assertEqual(compilerInstance.getScriptKind("foo.js"), ScriptKind.JS);
+  assertEqual(compilerInstance.getScriptKind("foo.json"), ScriptKind.JSON);
+  assertEqual(compilerInstance.getScriptKind("foo.txt"), ScriptKind.JS);
+});
+
+test(function compilerGetScriptVersion() {
+  const moduleMetaData = compilerInstance.resolveModule(
+    "foo/bar.ts",
+    "/root/project"
+  );
+  assertEqual(
+    compilerInstance.getScriptVersion(moduleMetaData.fileName),
+    "1",
+    "Expected known module to have script version of 1"
+  );
+});
+
+test(function compilerGetScriptVersionUnknown() {
+  assertEqual(
+    compilerInstance.getScriptVersion("/root/project/unknown_module.ts"),
+    "",
+    "Expected unknown module to have an empty script version"
+  );
+});
+
+test(function compilerGetScriptSnapshot() {
+  const moduleMetaData = compilerInstance.resolveModule(
+    "foo/bar.ts",
+    "/root/project"
+  );
+  const result = compilerInstance.getScriptSnapshot(moduleMetaData.fileName);
+  assert(result != null, "Expected snapshot to be defined.");
+  assertEqual(result.getLength(), fooBarTsSource.length);
+  assertEqual(
+    result.getText(0, 6),
+    "import",
+    "Expected .getText() to equal 'import'"
+  );
+  assertEqual(result.getChangeRange(result), undefined);
+  assert(!("dispose" in result));
+});
+
+test(function compilerGetCurrentDirectory() {
+  assertEqual(compilerInstance.getCurrentDirectory(), "");
+});
+
+test(function compilerGetDefaultLibFileName() {
+  assertEqual(
+    compilerInstance.getDefaultLibFileName(),
+    "$asset$/lib.globals.d.ts"
+  );
+});
+
+test(function compilerUseCaseSensitiveFileNames() {
+  assertEqual(compilerInstance.useCaseSensitiveFileNames(), true);
+});
+
+test(function compilerReadFile() {
+  let doesThrow = false;
+  try {
+    compilerInstance.readFile("foobar.ts");
+  } catch (e) {
+    doesThrow = true;
+    assert(e.message.includes("Not implemented") === true);
+  }
+  assert(doesThrow);
+});
+
+test(function compilerFileExists() {
+  const moduleMetaData = compilerInstance.resolveModule(
+    "foo/bar.ts",
+    "/root/project"
+  );
+  assert(compilerInstance.fileExists(moduleMetaData.fileName));
+  assert(compilerInstance.fileExists("$asset$/compiler.d.ts"));
+  assertEqual(
+    compilerInstance.fileExists("/root/project/unknown-module.ts"),
+    false
+  );
+});
+
+test(function compilerResolveModuleNames() {
+  const results = compilerInstance.resolveModuleNames(
+    ["foo/bar.ts", "foo/baz.ts", "$asset$/lib.globals.d.ts", "deno"],
+    "/root/project"
+  );
+  assertEqual(results.length, 4);
+  const fixtures: Array<[string, boolean]> = [
+    ["/root/project/foo/bar.ts", false],
+    ["/root/project/foo/baz.ts", false],
+    ["$asset$/lib.globals.d.ts", true],
+    ["$asset$/deno.d.ts", true]
+  ];
+  for (let i = 0; i < results.length; i++) {
+    const result = results[i];
+    const [resolvedFileName, isExternalLibraryImport] = fixtures[i];
+    assertEqual(result.resolvedFileName, resolvedFileName);
+    assertEqual(result.isExternalLibraryImport, isExternalLibraryImport);
+  }
+});
+
+// Remove the mocks
+test(function compilerTestsTeardown() {
+  Object.assign(compilerInstance, originals);
+});
diff --git a/js/globals.ts b/js/globals.ts
index ebfd3d265..beecbf58d 100644
--- a/js/globals.ts
+++ b/js/globals.ts
@@ -1,6 +1,7 @@
 // Copyright 2018 the Deno authors. All rights reserved. MIT license.
 
 import { Console } from "./console";
+import { exit } from "./os";
 import { RawSourceMap } from "./types";
 import * as timers from "./timers";
 import { TextEncoder, TextDecoder } from "./text_encoding";
@@ -9,6 +10,14 @@ import * as fetch_ from "./fetch";
 declare global {
   interface Window {
     console: Console;
+    define: Readonly<unknown>;
+    onerror?: (
+      message: string,
+      source: string,
+      lineno: number,
+      colno: number,
+      error: Error
+    ) => void;
   }
 
   const clearTimeout: typeof timers.clearTimer;
@@ -58,6 +67,22 @@ window.clearTimeout = timers.clearTimer;
 window.clearInterval = timers.clearTimer;
 
 window.console = new Console(libdeno.print);
+// Uncaught exceptions are sent to window.onerror by the privileged binding.
+window.onerror = (
+  message: string,
+  source: string,
+  lineno: number,
+  colno: number,
+  error: Error
+) => {
+  // TODO Currently there is a bug in v8_source_maps.ts that causes a
+  // segfault if it is used within window.onerror. To workaround we
+  // uninstall the Error.prepareStackTrace handler. Users will get unmapped
+  // stack traces on uncaught exceptions until this issue is fixed.
+  //Error.prepareStackTrace = null;
+  console.log(error.stack);
+  exit(1);
+};
 window.TextEncoder = TextEncoder;
 window.TextDecoder = TextDecoder;
 
diff --git a/js/main.ts b/js/main.ts
index d035f9ba6..740003049 100644
--- a/js/main.ts
+++ b/js/main.ts
@@ -1,10 +1,9 @@
 // Copyright 2018 the Deno authors. All rights reserved. MIT license.
 import { flatbuffers } from "flatbuffers";
 import { deno as fbs } from "gen/msg_generated";
-import { assert, log, assignCmdId } from "./util";
-import * as util from "./util";
+import { assert, assignCmdId, log, setLogDebug } from "./util";
 import * as os from "./os";
-import * as runtime from "./runtime";
+import { DenoCompiler } from "./compiler";
 import { libdeno } from "./globals";
 import * as timers from "./timers";
 import { onFetchRes } from "./fetch";
@@ -47,7 +46,7 @@ function onMessage(ui8: Uint8Array) {
 /* tslint:disable-next-line:no-default-export */
 export default function denoMain() {
   libdeno.recv(onMessage);
-  runtime.setup();
+  const compiler = DenoCompiler.instance();
 
   // First we send an empty "Start" message to let the privlaged side know we
   // are ready. The response should be a "StartRes" message containing the CLI
@@ -69,7 +68,7 @@ export default function denoMain() {
   const startResMsg = new fbs.StartRes();
   assert(base.msg(startResMsg) != null);
 
-  util.setLogDebug(startResMsg.debugFlag());
+  setLogDebug(startResMsg.debugFlag());
 
   const cwd = startResMsg.cwd();
   log("cwd", cwd);
@@ -86,8 +85,5 @@ export default function denoMain() {
     os.exit(1);
   }
 
-  const mod = runtime.resolveModule(inputFn, `${cwd}/`);
-  assert(mod != null);
-  // TypeScript does not track assert, therefore not null assertion
-  mod!.compileAndRun();
+  compiler.run(inputFn, `${cwd}/`);
 }
diff --git a/js/runtime.ts b/js/runtime.ts
deleted file mode 100644
index 93649e11c..000000000
--- a/js/runtime.ts
+++ /dev/null
@@ -1,376 +0,0 @@
-// Copyright 2018 the Deno authors. All rights reserved. MIT license.
-// Glossary
-// outputCode = generated javascript code
-// sourceCode = typescript code (or input javascript code)
-// moduleName = a resolved module name
-// fileName = an unresolved raw fileName.
-//            for http modules , its the path to the locally downloaded
-//            version.
-
-import * as ts from "typescript";
-import * as util from "./util";
-import { log } from "./util";
-import { assetSourceCode } from "./assets";
-import * as os from "./os";
-import * as sourceMaps from "./v8_source_maps";
-import { libdeno, window, globalEval } from "./globals";
-import * as deno from "./deno";
-import { RawSourceMap } from "./types";
-
-const EOL = "\n";
-const ASSETS = "/$asset$/";
-
-// tslint:disable-next-line:no-any
-export type AmdFactory = (...args: any[]) => undefined | object;
-export type AmdDefine = (deps: string[], factory: AmdFactory) => void;
-
-// Uncaught exceptions are sent to window.onerror by the privlaged binding.
-window.onerror = (
-  message: string,
-  source: string,
-  lineno: number,
-  colno: number,
-  error: Error
-) => {
-  // TODO Currently there is a bug in v8_source_maps.ts that causes a segfault
-  // if it is used within window.onerror. To workaround we uninstall the
-  // Error.prepareStackTrace handler. Users will get unmapped stack traces on
-  // uncaught exceptions until this issue is fixed.
-  //Error.prepareStackTrace = null;
-  console.log(error.stack);
-  os.exit(1);
-};
-
-export function setup(): void {
-  sourceMaps.install({
-    installPrepareStackTrace: true,
-    getGeneratedContents: (filename: string): string | RawSourceMap => {
-      util.log("getGeneratedContents", filename);
-      if (filename === "gen/bundle/main.js") {
-        util.assert(libdeno.mainSource.length > 0);
-        return libdeno.mainSource;
-      } else if (filename === "main.js.map") {
-        return libdeno.mainSourceMap;
-      } else if (filename === "deno_main.js") {
-        return "";
-      } else {
-        const mod = FileModule.load(filename);
-        if (!mod) {
-          util.log("getGeneratedContents cannot find", filename);
-          return "";
-        }
-        return mod.outputCode;
-      }
-    }
-  });
-}
-
-// This class represents a module. We call it FileModule to make it explicit
-// that each module represents a single file.
-// Access to FileModule instances should only be done thru the static method
-// FileModule.load(). FileModules are NOT executed upon first load, only when
-// compileAndRun is called.
-export class FileModule {
-  scriptVersion = "";
-  readonly exports = {};
-
-  private static readonly map = new Map<string, FileModule>();
-  constructor(
-    readonly fileName: string,
-    readonly sourceCode = "",
-    public outputCode = ""
-  ) {
-    util.assert(
-      !FileModule.map.has(fileName),
-      `FileModule.map already has ${fileName}`
-    );
-    FileModule.map.set(fileName, this);
-    if (outputCode !== "") {
-      this.scriptVersion = "1";
-    }
-  }
-
-  compileAndRun(): void {
-    util.log("compileAndRun", this.sourceCode);
-    if (!this.outputCode) {
-      // If there is no cached outputCode, then compile the code.
-      util.assert(
-        this.sourceCode != null && this.sourceCode.length > 0,
-        `Have no source code from ${this.fileName}`
-      );
-      const compiler = Compiler.instance();
-      this.outputCode = compiler.compile(this.fileName);
-      os.codeCache(this.fileName, this.sourceCode, this.outputCode);
-    }
-    execute(this.fileName, this.outputCode);
-  }
-
-  static load(fileName: string): FileModule | undefined {
-    return this.map.get(fileName);
-  }
-
-  static getScriptsWithSourceCode(): string[] {
-    const out = [];
-    for (const fn of this.map.keys()) {
-      const m = this.map.get(fn);
-      if (m && m.sourceCode) {
-        out.push(fn);
-      }
-    }
-    return out;
-  }
-}
-
-export function makeDefine(fileName: string): AmdDefine {
-  const localDefine = (deps: string[], factory: AmdFactory): void => {
-    const localRequire = (x: string) => {
-      log("localRequire", x);
-    };
-    const currentModule = FileModule.load(fileName);
-    util.assert(currentModule != null);
-    const localExports = currentModule!.exports;
-    log("localDefine", fileName, deps, localExports);
-    const args = deps.map(dep => {
-      if (dep === "require") {
-        return localRequire;
-      } else if (dep === "exports") {
-        return localExports;
-      } else if (dep === "typescript") {
-        return ts;
-      } else if (dep === "deno") {
-        return deno;
-      } else {
-        const resolved = resolveModuleName(dep, fileName);
-        util.assert(resolved != null);
-        const depModule = FileModule.load(resolved!);
-        if (depModule) {
-          depModule.compileAndRun();
-          return depModule.exports;
-        }
-        return undefined;
-      }
-    });
-    factory(...args);
-  };
-  return localDefine;
-}
-
-export function resolveModule(
-  moduleSpecifier: string,
-  containingFile: string
-): null | FileModule {
-  util.log("resolveModule", { moduleSpecifier, containingFile });
-  util.assert(moduleSpecifier != null && moduleSpecifier.length > 0);
-  let filename: string | null;
-  let sourceCode: string | null;
-  let outputCode: string | null;
-  if (moduleSpecifier.startsWith(ASSETS) || containingFile.startsWith(ASSETS)) {
-    // Assets are compiled into the runtime javascript bundle.
-    // we _know_ `.pop()` will return a string, but TypeScript doesn't so
-    // not null assertion
-    const moduleId = moduleSpecifier.split("/").pop()!;
-    const assetName = moduleId.includes(".") ? moduleId : `${moduleId}.d.ts`;
-    util.assert(assetName in assetSourceCode, `No such asset "${assetName}"`);
-    sourceCode = assetSourceCode[assetName];
-    filename = ASSETS + assetName;
-  } else {
-    // We query Rust with a CodeFetch message. It will load the sourceCode, and
-    // if there is any outputCode cached, will return that as well.
-    const fetchResponse = os.codeFetch(moduleSpecifier, containingFile);
-    filename = fetchResponse.filename;
-    sourceCode = fetchResponse.sourceCode;
-    outputCode = fetchResponse.outputCode;
-  }
-  if (sourceCode == null || sourceCode.length === 0 || filename == null) {
-    return null;
-  }
-  util.log("resolveModule sourceCode length ", sourceCode.length);
-  const m = FileModule.load(filename);
-  if (m != null) {
-    return m;
-  } else {
-    // null and undefined are incompatible in strict mode, but outputCode being
-    // null here has no runtime behavior impact, therefore not null assertion
-    return new FileModule(filename, sourceCode, outputCode!);
-  }
-}
-
-function resolveModuleName(
-  moduleSpecifier: string,
-  containingFile: string
-): string | undefined {
-  const mod = resolveModule(moduleSpecifier, containingFile);
-  if (mod) {
-    return mod.fileName;
-  } else {
-    return undefined;
-  }
-}
-
-function execute(fileName: string, outputCode: string): void {
-  util.assert(outputCode != null && outputCode.length > 0);
-  window["define"] = makeDefine(fileName);
-  outputCode += `\n//# sourceURL=${fileName}`;
-  globalEval(outputCode);
-  window["define"] = null;
-}
-
-// This is a singleton class. Use Compiler.instance() to access.
-class Compiler {
-  options: ts.CompilerOptions = {
-    allowJs: true,
-    module: ts.ModuleKind.AMD,
-    outDir: "$deno$",
-    inlineSourceMap: true,
-    inlineSources: true,
-    target: ts.ScriptTarget.ESNext
-  };
-  /*
-  allowJs: true,
-  module: ts.ModuleKind.AMD,
-  noEmit: false,
-  outDir: '$deno$',
-  */
-  private service: ts.LanguageService;
-
-  private constructor() {
-    const host = new TypeScriptHost(this.options);
-    this.service = ts.createLanguageService(host);
-  }
-
-  private static _instance: Compiler;
-  static instance(): Compiler {
-    return this._instance || (this._instance = new this());
-  }
-
-  compile(fileName: string): string {
-    const output = this.service.getEmitOutput(fileName);
-
-    // Get the relevant diagnostics - this is 3x faster than
-    // `getPreEmitDiagnostics`.
-    const diagnostics = this.service
-      .getCompilerOptionsDiagnostics()
-      .concat(this.service.getSyntacticDiagnostics(fileName))
-      .concat(this.service.getSemanticDiagnostics(fileName));
-    if (diagnostics.length > 0) {
-      const errMsg = ts.formatDiagnosticsWithColorAndContext(
-        diagnostics,
-        formatDiagnosticsHost
-      );
-      console.log(errMsg);
-      os.exit(1);
-    }
-
-    util.assert(!output.emitSkipped);
-
-    const outputCode = output.outputFiles[0].text;
-    // let sourceMapCode = output.outputFiles[0].text;
-    return outputCode;
-  }
-}
-
-// Create the compiler host for type checking.
-class TypeScriptHost implements ts.LanguageServiceHost {
-  constructor(readonly options: ts.CompilerOptions) {}
-
-  getScriptFileNames(): string[] {
-    const keys = FileModule.getScriptsWithSourceCode();
-    util.log("getScriptFileNames", keys);
-    return keys;
-  }
-
-  getScriptVersion(fileName: string): string {
-    util.log("getScriptVersion", fileName);
-    const m = FileModule.load(fileName);
-    return (m && m.scriptVersion) || "";
-  }
-
-  getScriptSnapshot(fileName: string): ts.IScriptSnapshot | undefined {
-    util.log("getScriptSnapshot", fileName);
-    const m = resolveModule(fileName, ".");
-    if (m == null) {
-      util.log("getScriptSnapshot", fileName, "NOT FOUND");
-      return undefined;
-    }
-    //const m = resolveModule(fileName, ".");
-    util.assert(m.sourceCode.length > 0);
-    return ts.ScriptSnapshot.fromString(m.sourceCode);
-  }
-
-  fileExists(fileName: string): boolean {
-    const m = resolveModule(fileName, ".");
-    const exists = m != null;
-    util.log("fileExist", fileName, exists);
-    return exists;
-  }
-
-  readFile(path: string, encoding?: string): string | undefined {
-    util.log("readFile", path);
-    return util.notImplemented();
-  }
-
-  getNewLine() {
-    return EOL;
-  }
-
-  getCurrentDirectory() {
-    util.log("getCurrentDirectory");
-    return ".";
-  }
-
-  getCompilationSettings() {
-    util.log("getCompilationSettings");
-    return this.options;
-  }
-
-  getDefaultLibFileName(options: ts.CompilerOptions): string {
-    const fn = "lib.globals.d.ts"; // ts.getDefaultLibFileName(options);
-    util.log("getDefaultLibFileName", fn);
-    const m = resolveModule(fn, ASSETS);
-    util.assert(m != null);
-    // TypeScript cannot track assertions, therefore not null assertion
-    return m!.fileName;
-  }
-
-  resolveModuleNames(
-    moduleNames: string[],
-    containingFile: string
-  ): ts.ResolvedModule[] {
-    //util.log("resolveModuleNames", { moduleNames, reusedNames });
-    return moduleNames.map(name => {
-      let resolvedFileName;
-      if (name === "deno") {
-        resolvedFileName = resolveModuleName("deno.d.ts", ASSETS);
-      } else if (name === "typescript") {
-        resolvedFileName = resolveModuleName("typescript.d.ts", ASSETS);
-      } else {
-        resolvedFileName = resolveModuleName(name, containingFile);
-      }
-      // According to the interface we shouldn't return `undefined` but if we
-      // fail to return the same length of modules to those we cannot resolve
-      // then TypeScript fails on an assertion that the lengths can't be
-      // different, so we have to return an "empty" resolved module
-      // TODO: all this does is push the problem downstream, and TypeScript
-      // will complain it can't identify the type of the file and throw
-      // a runtime exception, so we need to handle missing modules better
-      resolvedFileName = resolvedFileName || "";
-      // This flags to the compiler to not go looking to transpile functional
-      // code, anything that is in `/$asset$/` is just library code
-      const isExternalLibraryImport = resolvedFileName.startsWith(ASSETS);
-      // TODO: we should be returning a ts.ResolveModuleFull
-      return { resolvedFileName, isExternalLibraryImport };
-    });
-  }
-}
-
-const formatDiagnosticsHost: ts.FormatDiagnosticsHost = {
-  getCurrentDirectory(): string {
-    return ".";
-  },
-  getCanonicalFileName(fileName: string): string {
-    return fileName;
-  },
-  getNewLine(): string {
-    return EOL;
-  }
-};
diff --git a/js/tsconfig.generated.json b/js/tsconfig.generated.json
index 4d76dd98f..d3cacd73e 100644
--- a/js/tsconfig.generated.json
+++ b/js/tsconfig.generated.json
@@ -11,6 +11,7 @@
   },
   "files": [
     "../node_modules/typescript/lib/lib.esnext.d.ts",
+    "./compiler.ts",
     "./deno.ts",
     "./globals.ts"
   ]
diff --git a/js/unit_tests.ts b/js/unit_tests.ts
index ef65519f6..f203444fa 100644
--- a/js/unit_tests.ts
+++ b/js/unit_tests.ts
@@ -6,6 +6,8 @@
 import { test, assert, assertEqual } from "./testing/testing.ts";
 import { readFileSync } from "deno";
 
+import "./compiler_test.ts";
+
 test(async function tests_test() {
   assert(true);
 });
diff --git a/tests/013_dynamic_import.ts b/tests/013_dynamic_import.ts
new file mode 100644
index 000000000..0812623f6
--- /dev/null
+++ b/tests/013_dynamic_import.ts
@@ -0,0 +1,17 @@
+(async () => {
+  const {
+    returnsHi,
+    returnsFoo2,
+    printHello3
+  } = await import("./subdir/mod1.ts");
+
+  printHello3();
+
+  if (returnsHi() !== "Hi") {
+    throw Error("Unexpected");
+  }
+
+  if (returnsFoo2() !== "Foo") {
+    throw Error("Unexpected");
+  }
+})();
diff --git a/tests/013_dynamic_import.ts.out b/tests/013_dynamic_import.ts.out
new file mode 100644
index 000000000..e965047ad
--- /dev/null
+++ b/tests/013_dynamic_import.ts.out
@@ -0,0 +1 @@
+Hello
diff --git a/tests/async_error.ts.out b/tests/async_error.ts.out
index c98c79bfc..f282f6c3e 100644
--- a/tests/async_error.ts.out
+++ b/tests/async_error.ts.out
@@ -3,8 +3,7 @@ before error
 Error: error
     at foo ([WILDCARD]tests/async_error.ts:4:9)
     at eval ([WILDCARD]tests/async_error.ts:7:1)
-    at eval (<anonymous>)
-    at execute (deno/js/runtime.ts:[WILDCARD])
-    at FileModule.compileAndRun (deno/js/runtime.ts:[WILDCARD])
+    at DenoCompiler.eval [as _globalEval] (<anonymous>)
+    at DenoCompiler.run (deno/js/compiler.ts:[WILDCARD])
     at denoMain (deno/js/main.ts:[WILDCARD])
     at deno_main.js:1:1
diff --git a/tests/error_001.ts.out b/tests/error_001.ts.out
index 237af9d57..04d9abb96 100644
--- a/tests/error_001.ts.out
+++ b/tests/error_001.ts.out
@@ -2,8 +2,7 @@ Error: bad
     at foo (file://[WILDCARD]tests/error_001.ts:2:9)
     at bar (file://[WILDCARD]tests/error_001.ts:6:3)
     at eval (file://[WILDCARD]tests/error_001.ts:9:1)
-    at eval (<anonymous>)
-    at execute (deno/js/runtime.ts:[WILDCARD])
-    at FileModule.compileAndRun (deno/js/runtime.ts:[WILDCARD])
+    at DenoCompiler.eval [as _globalEval] (<anonymous>)
+    at DenoCompiler.run (deno/js/compiler.ts:[WILDCARD])
     at denoMain (deno/js/main.ts:[WILDCARD])
     at deno_main.js:1:1
diff --git a/tests/error_002.ts.out b/tests/error_002.ts.out
index f245ab7c0..20eb0c842 100644
--- a/tests/error_002.ts.out
+++ b/tests/error_002.ts.out
@@ -2,10 +2,9 @@ Error: exception from mod1
     at Object.throwsError (file://[WILDCARD]tests/subdir/mod1.ts:16:9)
     at foo (file://[WILDCARD]tests/error_002.ts:4:3)
     at eval (file://[WILDCARD]tests/error_002.ts:7:1)
-    at localDefine (deno/js/runtime.ts:[WILDCARD])
+    at localDefine (deno/js/compiler.ts:[WILDCARD])
     at eval ([WILDCARD]tests/error_002.ts, <anonymous>)
-    at eval (<anonymous>)
-    at execute (deno/js/runtime.ts:[WILDCARD])
-    at FileModule.compileAndRun (deno/js/runtime.ts:[WILDCARD])
+    at DenoCompiler.eval [as _globalEval] (<anonymous>)
+    at DenoCompiler.run (deno/js/compiler.ts:[WILDCARD])
     at denoMain (deno/js/main.ts:[WILDCARD])
     at deno_main.js:1:1
diff --git a/tests/error_003_typescript.ts b/tests/error_003_typescript.ts
new file mode 100644
index 000000000..ebd9fcbe6
--- /dev/null
+++ b/tests/error_003_typescript.ts
@@ -0,0 +1,2 @@
+// console.log intentionally misspelled to trigger TypeScript error
+consol.log("hello world!");
diff --git a/tests/error_003_typescript.ts.out b/tests/error_003_typescript.ts.out
new file mode 100644
index 000000000..f04be363b
--- /dev/null
+++ b/tests/error_003_typescript.ts.out
@@ -0,0 +1,10 @@
+[WILDCARD]tests/error_003_typescript.tsILDCARD] - error TS2552: Cannot find name 'consol'. Did you mean 'console'?
+
+[WILDCARD][0m consol.log("hello world!");
+  ~~~~~~
+
+  $asset$/globals.d.tsILDCARD]
+    [WILDCARD][0m     const console: Console;
+                 ~~~~~~~
+    'console' is declared here.
+
diff --git a/tests/error_004_missing_module.ts b/tests/error_004_missing_module.ts
new file mode 100644
index 000000000..48623320b
--- /dev/null
+++ b/tests/error_004_missing_module.ts
@@ -0,0 +1 @@
+import * as badModule from "bad-module.ts";
diff --git a/tests/error_004_missing_module.ts.out b/tests/error_004_missing_module.ts.out
new file mode 100644
index 000000000..dda14d25e
--- /dev/null
+++ b/tests/error_004_missing_module.ts.out
@@ -0,0 +1,12 @@
+Error: Cannot resolve module "bad-module.ts" from "[WILDCARD]error_004_missing_module.ts".
+  os.codeFetch message: [WILDCARD] (os error 2)
+    at throwResolutionError (deno/js/compiler.ts:[WILDCARD])
+    at DenoCompiler.resolveModule (deno/js/compiler.ts:[WILDCARD])
+    at DenoCompiler.resolveModuleName (deno/js/compiler.ts:[WILDCARD])
+    at moduleNames.map.name (deno/js/compiler.ts:[WILDCARD])
+    at Array.map (<anonymous>)
+    at DenoCompiler.resolveModuleNames (deno/js/compiler.ts:[WILDCARD])
+    at Object.compilerHost.resolveModuleNames (deno/third_party/node_modules/typescript/lib/typescript.js:[WILDCARD])
+    at resolveModuleNamesWorker (deno/third_party/node_modules/typescript/lib/typescript.js:[WILDCARD])
+    at resolveModuleNamesReusingOldState (deno/third_party/node_modules/typescript/lib/typescript.js:[WILDCARD])
+    at processImportedModules (deno/third_party/node_modules/typescript/lib/typescript.js:[WILDCARD])