reorg: move JS ops implementations to cli/js/ops/, part 1 (#4264)

Following JS ops were moved to separate files in cli/js/ops directory:
- compiler
- dispatch_json
- dispatch_minimal
- errors
- fetch
- fs_events
- os
- random
- repl
- resources
- runtime_compiler
- runtime
- tty

13 files changed, 790 insertions, 0 deletions

diff --git a/cli/js/ops/compiler.ts b/cli/js/ops/compiler.ts
new file mode 100644
index 000000000..b45ad42b2
--- /dev/null
+++ b/cli/js/ops/compiler.ts
@@ -0,0 +1,55 @@
+// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
+
+import { sendAsync, sendSync } from "./dispatch_json.ts";
+import { TextDecoder, TextEncoder } from "../web/text_encoding.ts";
+import { core } from "../core.ts";
+
+/** Ops to Rust to resolve modules' URLs. */
+export function resolveModules(
+  specifiers: string[],
+  referrer?: string
+): string[] {
+  return sendSync("op_resolve_modules", { specifiers, referrer });
+}
+
+/** Ops to Rust to fetch modules meta data. */
+export function fetchSourceFiles(
+  specifiers: string[],
+  referrer?: string
+): Promise<
+  Array<{
+    url: string;
+    filename: string;
+    mediaType: number;
+    sourceCode: string;
+  }>
+> {
+  return sendAsync("op_fetch_source_files", {
+    specifiers,
+    referrer
+  });
+}
+
+const encoder = new TextEncoder();
+const decoder = new TextDecoder();
+
+/** This op is also used during snapshotting */
+export function getAsset(name: string): string {
+  const opId = core.ops()["op_fetch_asset"];
+  // We really don't want to depend on JSON dispatch during snapshotting, so
+  // this op exchanges strings with Rust as raw byte arrays.
+  const sourceCodeBytes = core.dispatch(opId, encoder.encode(name));
+  return decoder.decode(sourceCodeBytes!);
+}
+
+export function cache(
+  extension: string,
+  moduleId: string,
+  contents: string
+): void {
+  sendSync("op_cache", {
+    extension,
+    moduleId,
+    contents
+  });
+}
diff --git a/cli/js/ops/dispatch_json.ts b/cli/js/ops/dispatch_json.ts
new file mode 100644
index 000000000..6fb9007df
--- /dev/null
+++ b/cli/js/ops/dispatch_json.ts
@@ -0,0 +1,97 @@
+// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
+import * as util from "../util.ts";
+import { TextEncoder, TextDecoder } from "../web/text_encoding.ts";
+import { core } from "../core.ts";
+import { OPS_CACHE } from "../runtime.ts";
+import { ErrorKind, getErrorClass } from "../errors.ts";
+
+// eslint-disable-next-line @typescript-eslint/no-explicit-any
+type Ok = any;
+
+interface JsonError {
+  kind: ErrorKind;
+  message: string;
+}
+
+interface JsonResponse {
+  ok?: Ok;
+  err?: JsonError;
+  promiseId?: number; // Only present in async messages.
+}
+
+const promiseTable = new Map<number, util.Resolvable<JsonResponse>>();
+let _nextPromiseId = 1;
+
+function nextPromiseId(): number {
+  return _nextPromiseId++;
+}
+
+function decode(ui8: Uint8Array): JsonResponse {
+  const s = new TextDecoder().decode(ui8);
+  return JSON.parse(s) as JsonResponse;
+}
+
+function encode(args: object): Uint8Array {
+  const s = JSON.stringify(args);
+  return new TextEncoder().encode(s);
+}
+
+function unwrapResponse(res: JsonResponse): Ok {
+  if (res.err != null) {
+    throw new (getErrorClass(res.err.kind))(res.err.message);
+  }
+  util.assert(res.ok != null);
+  return res.ok;
+}
+
+export function asyncMsgFromRust(resUi8: Uint8Array): void {
+  const res = decode(resUi8);
+  util.assert(res.promiseId != null);
+
+  const promise = promiseTable.get(res.promiseId!);
+  util.assert(promise != null);
+  promiseTable.delete(res.promiseId!);
+  promise.resolve(res);
+}
+
+export function sendSync(
+  opName: string,
+  args: object = {},
+  zeroCopy?: Uint8Array
+): Ok {
+  const opId = OPS_CACHE[opName];
+  util.log("sendSync", opName, opId);
+  const argsUi8 = encode(args);
+  const resUi8 = core.dispatch(opId, argsUi8, zeroCopy);
+  util.assert(resUi8 != null);
+
+  const res = decode(resUi8);
+  util.assert(res.promiseId == null);
+  return unwrapResponse(res);
+}
+
+export async function sendAsync(
+  opName: string,
+  args: object = {},
+  zeroCopy?: Uint8Array
+): Promise<Ok> {
+  const opId = OPS_CACHE[opName];
+  util.log("sendAsync", opName, opId);
+  const promiseId = nextPromiseId();
+  args = Object.assign(args, { promiseId });
+  const promise = util.createResolvable<Ok>();
+
+  const argsUi8 = encode(args);
+  const buf = core.dispatch(opId, argsUi8, zeroCopy);
+  if (buf) {
+    // Sync result.
+    const res = decode(buf);
+    promise.resolve(res);
+  } else {
+    // Async result.
+    promiseTable.set(promiseId, promise);
+  }
+
+  const res = await promise;
+  return unwrapResponse(res);
+}
diff --git a/cli/js/ops/dispatch_minimal.ts b/cli/js/ops/dispatch_minimal.ts
new file mode 100644
index 000000000..7aec4683c
--- /dev/null
+++ b/cli/js/ops/dispatch_minimal.ts
@@ -0,0 +1,115 @@
+// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
+import * as util from "../util.ts";
+import { core } from "../core.ts";
+import { TextDecoder } from "../web/text_encoding.ts";
+import { ErrorKind, errors, getErrorClass } from "../errors.ts";
+
+const promiseTableMin = new Map<number, util.Resolvable<RecordMinimal>>();
+// Note it's important that promiseId starts at 1 instead of 0, because sync
+// messages are indicated with promiseId 0. If we ever add wrap around logic for
+// overflows, this should be taken into account.
+let _nextPromiseId = 1;
+
+const decoder = new TextDecoder();
+
+function nextPromiseId(): number {
+  return _nextPromiseId++;
+}
+
+export interface RecordMinimal {
+  promiseId: number;
+  arg: number;
+  result: number;
+  err?: {
+    kind: ErrorKind;
+    message: string;
+  };
+}
+
+export function recordFromBufMinimal(ui8: Uint8Array): RecordMinimal {
+  const header = ui8.subarray(0, 12);
+  const buf32 = new Int32Array(
+    header.buffer,
+    header.byteOffset,
+    header.byteLength / 4
+  );
+  const promiseId = buf32[0];
+  const arg = buf32[1];
+  const result = buf32[2];
+  let err;
+
+  if (arg < 0) {
+    const kind = result as ErrorKind;
+    const message = decoder.decode(ui8.subarray(12));
+    err = { kind, message };
+  } else if (ui8.length != 12) {
+    throw new errors.InvalidData("BadMessage");
+  }
+
+  return {
+    promiseId,
+    arg,
+    result,
+    err
+  };
+}
+
+function unwrapResponse(res: RecordMinimal): number {
+  if (res.err != null) {
+    throw new (getErrorClass(res.err.kind))(res.err.message);
+  }
+  return res.result;
+}
+
+const scratch32 = new Int32Array(3);
+const scratchBytes = new Uint8Array(
+  scratch32.buffer,
+  scratch32.byteOffset,
+  scratch32.byteLength
+);
+util.assert(scratchBytes.byteLength === scratch32.length * 4);
+
+export function asyncMsgFromRust(ui8: Uint8Array): void {
+  const record = recordFromBufMinimal(ui8);
+  const { promiseId } = record;
+  const promise = promiseTableMin.get(promiseId);
+  promiseTableMin.delete(promiseId);
+  util.assert(promise);
+  promise.resolve(record);
+}
+
+export async function sendAsyncMinimal(
+  opId: number,
+  arg: number,
+  zeroCopy: Uint8Array
+): Promise<number> {
+  const promiseId = nextPromiseId(); // AKA cmdId
+  scratch32[0] = promiseId;
+  scratch32[1] = arg;
+  scratch32[2] = 0; // result
+  const promise = util.createResolvable<RecordMinimal>();
+  const buf = core.dispatch(opId, scratchBytes, zeroCopy);
+  if (buf) {
+    const record = recordFromBufMinimal(buf);
+    // Sync result.
+    promise.resolve(record);
+  } else {
+    // Async result.
+    promiseTableMin.set(promiseId, promise);
+  }
+
+  const res = await promise;
+  return unwrapResponse(res);
+}
+
+export function sendSyncMinimal(
+  opId: number,
+  arg: number,
+  zeroCopy: Uint8Array
+): number {
+  scratch32[0] = 0; // promiseId 0 indicates sync
+  scratch32[1] = arg;
+  const res = core.dispatch(opId, scratchBytes, zeroCopy)!;
+  const resRecord = recordFromBufMinimal(res);
+  return unwrapResponse(resRecord);
+}
diff --git a/cli/js/ops/errors.ts b/cli/js/ops/errors.ts
new file mode 100644
index 000000000..f96e376d6
--- /dev/null
+++ b/cli/js/ops/errors.ts
@@ -0,0 +1,61 @@
+// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
+import { DiagnosticItem } from "../diagnostics.ts";
+import { sendSync } from "./dispatch_json.ts";
+
+/**
+ * Format an array of diagnostic items and return them as a single string.
+ * @param items An array of diagnostic items to format
+ */
+export function formatDiagnostics(items: DiagnosticItem[]): string {
+  return sendSync("op_format_diagnostic", { items });
+}
+
+export interface Location {
+  /** The full url for the module, e.g. `file://some/file.ts` or
+   * `https://some/file.ts`. */
+  filename: string;
+
+  /** The line number in the file.  It is assumed to be 1-indexed. */
+  line: number;
+
+  /** The column number in the file.  It is assumed to be 1-indexed. */
+  column: number;
+}
+
+/** Given a current location in a module, lookup the source location and
+ * return it.
+ *
+ * When Deno transpiles code, it keep source maps of the transpiled code.  This
+ * function can be used to lookup the original location.  This is automatically
+ * done when accessing the `.stack` of an error, or when an uncaught error is
+ * logged.  This function can be used to perform the lookup for creating better
+ * error handling.
+ *
+ * **Note:** `line` and `column` are 1 indexed, which matches display
+ * expectations, but is not typical of most index numbers in Deno.
+ *
+ * An example:
+ *
+ *       const orig = Deno.applySourceMap({
+ *         location: "file://my/module.ts",
+ *         line: 5,
+ *         column: 15
+ *       });
+ *       console.log(`${orig.filename}:${orig.line}:${orig.column}`);
+ *
+ */
+export function applySourceMap(location: Location): Location {
+  const { filename, line, column } = location;
+  // On this side, line/column are 1 based, but in the source maps, they are
+  // 0 based, so we have to convert back and forth
+  const res = sendSync("op_apply_source_map", {
+    filename,
+    line: line - 1,
+    column: column - 1
+  });
+  return {
+    filename: res.filename,
+    line: res.line + 1,
+    column: res.column + 1
+  };
+}
diff --git a/cli/js/ops/fetch.ts b/cli/js/ops/fetch.ts
new file mode 100644
index 000000000..c5c0cb883
--- /dev/null
+++ b/cli/js/ops/fetch.ts
@@ -0,0 +1,28 @@
+// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
+
+import { sendAsync } from "./dispatch_json.ts";
+
+interface FetchRequest {
+  url: string;
+  method: string | null;
+  headers: Array<[string, string]>;
+}
+
+export interface FetchResponse {
+  bodyRid: number;
+  status: number;
+  statusText: string;
+  headers: Array<[string, string]>;
+}
+
+export async function fetch(
+  args: FetchRequest,
+  body: ArrayBufferView | undefined
+): Promise<FetchResponse> {
+  let zeroCopy = undefined;
+  if (body) {
+    zeroCopy = new Uint8Array(body.buffer, body.byteOffset, body.byteLength);
+  }
+
+  return await sendAsync("op_fetch", args, zeroCopy);
+}
diff --git a/cli/js/ops/fs_events.ts b/cli/js/ops/fs_events.ts
new file mode 100644
index 000000000..09e82c515
--- /dev/null
+++ b/cli/js/ops/fs_events.ts
@@ -0,0 +1,39 @@
+// Copyright 2019 the Deno authors. All rights reserved. MIT license.
+import { sendSync, sendAsync } from "./dispatch_json.ts";
+import { close } from "./resources.ts";
+
+export interface FsEvent {
+  kind: "any" | "access" | "create" | "modify" | "remove";
+  paths: string[];
+}
+
+class FsEvents implements AsyncIterableIterator<FsEvent> {
+  readonly rid: number;
+
+  constructor(paths: string[], options: { recursive: boolean }) {
+    const { recursive } = options;
+    this.rid = sendSync("op_fs_events_open", { recursive, paths });
+  }
+
+  async next(): Promise<IteratorResult<FsEvent>> {
+    return await sendAsync("op_fs_events_poll", {
+      rid: this.rid
+    });
+  }
+
+  async return(value?: FsEvent): Promise<IteratorResult<FsEvent>> {
+    close(this.rid);
+    return { value, done: true };
+  }
+
+  [Symbol.asyncIterator](): AsyncIterableIterator<FsEvent> {
+    return this;
+  }
+}
+
+export function fsEvents(
+  paths: string | string[],
+  options = { recursive: true }
+): AsyncIterableIterator<FsEvent> {
+  return new FsEvents(Array.isArray(paths) ? paths : [paths], options);
+}
diff --git a/cli/js/ops/get_random_values.ts b/cli/js/ops/get_random_values.ts
new file mode 100644
index 000000000..0e384c259
--- /dev/null
+++ b/cli/js/ops/get_random_values.ts
@@ -0,0 +1,30 @@
+// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
+import { sendSync } from "./dispatch_json.ts";
+import { assert } from "../util.ts";
+
+/** Synchronously collects cryptographically secure random values. The
+ * underlying CSPRNG in use is Rust's `rand::rngs::ThreadRng`.
+ *
+ *       const arr = new Uint8Array(32);
+ *       crypto.getRandomValues(arr);
+ */
+export function getRandomValues<
+  T extends
+    | Int8Array
+    | Uint8Array
+    | Uint8ClampedArray
+    | Int16Array
+    | Uint16Array
+    | Int32Array
+    | Uint32Array
+>(typedArray: T): T {
+  assert(typedArray !== null, "Input must not be null");
+  assert(typedArray.length <= 65536, "Input must not be longer than 65536");
+  const ui8 = new Uint8Array(
+    typedArray.buffer,
+    typedArray.byteOffset,
+    typedArray.byteLength
+  );
+  sendSync("op_get_random_values", {}, ui8);
+  return typedArray;
+}
diff --git a/cli/js/ops/os.ts b/cli/js/ops/os.ts
new file mode 100644
index 000000000..2d27f7ef5
--- /dev/null
+++ b/cli/js/ops/os.ts
@@ -0,0 +1,227 @@
+// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
+import { sendSync } from "./dispatch_json.ts";
+import { errors } from "../errors.ts";
+import * as util from "../util.ts";
+
+/** Get the loadavg.
+ * Requires the `--allow-env` flag.
+ *
+ *       console.log(Deno.loadavg());
+ */
+export function loadavg(): number[] {
+  return sendSync("op_loadavg");
+}
+
+/** Get the hostname.
+ * Requires the `--allow-env` flag.
+ *
+ *       console.log(Deno.hostname());
+ */
+export function hostname(): string {
+  return sendSync("op_hostname");
+}
+
+/** Get OS release.
+ * Requires the `--allow-env` flag.
+ *
+ *       console.log(Deno.osRelease());
+ */
+export function osRelease(): string {
+  return sendSync("op_os_release");
+}
+
+/** Exit the Deno process with optional exit code. */
+export function exit(code = 0): never {
+  sendSync("op_exit", { code });
+  return util.unreachable();
+}
+
+function setEnv(key: string, value: string): void {
+  sendSync("op_set_env", { key, value });
+}
+
+function getEnv(key: string): string | undefined {
+  return sendSync("op_get_env", { key })[0];
+}
+
+/** Returns a snapshot of the environment variables at invocation. Mutating a
+ * property in the object will set that variable in the environment for
+ * the process. The environment object will only accept `string`s
+ * as values.
+ *
+ *       console.log(Deno.env("SHELL"));
+ *       const myEnv = Deno.env();
+ *       console.log(myEnv.SHELL);
+ *       myEnv.TEST_VAR = "HELLO";
+ *       const newEnv = Deno.env();
+ *       console.log(myEnv.TEST_VAR == newEnv.TEST_VAR);
+ */
+export function env(): { [index: string]: string };
+export function env(key: string): string | undefined;
+export function env(
+  key?: string
+): { [index: string]: string } | string | undefined {
+  if (key) {
+    return getEnv(key);
+  }
+  const env = sendSync("op_env");
+  return new Proxy(env, {
+    set(obj, prop: string, value: string): boolean {
+      setEnv(prop, value);
+      return Reflect.set(obj, prop, value);
+    }
+  });
+}
+
+type DirKind =
+  | "home"
+  | "cache"
+  | "config"
+  | "executable"
+  | "data"
+  | "data_local"
+  | "audio"
+  | "desktop"
+  | "document"
+  | "download"
+  | "font"
+  | "picture"
+  | "public"
+  | "template"
+  | "tmp"
+  | "video";
+
+/**
+ * Returns the user and platform specific directories.
+ * Requires the `--allow-env` flag.
+ * Returns null if there is no applicable directory or if any other error
+ * occurs.
+ *
+ * Argument values: "home", "cache", "config", "executable", "data",
+ * "data_local", "audio", "desktop", "document", "download", "font", "picture",
+ * "public", "template", "video"
+ *
+ * "cache"
+ * |Platform | Value                               | Example                      |
+ * | ------- | ----------------------------------- | ---------------------------- |
+ * | Linux   | `$XDG_CACHE_HOME` or `$HOME`/.cache | /home/alice/.cache           |
+ * | macOS   | `$HOME`/Library/Caches              | /Users/Alice/Library/Caches  |
+ * | Windows | `{FOLDERID_LocalAppData}`           | C:\Users\Alice\AppData\Local |
+ *
+ * "config"
+ * |Platform | Value                                 | Example                          |
+ * | ------- | ------------------------------------- | -------------------------------- |
+ * | Linux   | `$XDG_CONFIG_HOME` or `$HOME`/.config | /home/alice/.config              |
+ * | macOS   | `$HOME`/Library/Preferences           | /Users/Alice/Library/Preferences |
+ * | Windows | `{FOLDERID_RoamingAppData}`           | C:\Users\Alice\AppData\Roaming   |
+ *
+ * "executable"
+ * |Platform | Value                                                           | Example                |
+ * | ------- | --------------------------------------------------------------- | -----------------------|
+ * | Linux   | `XDG_BIN_HOME` or `$XDG_DATA_HOME`/../bin or `$HOME`/.local/bin | /home/alice/.local/bin |
+ * | macOS   | -                                                               | -                      |
+ * | Windows | -                                                               | -                      |
+ *
+ * "data"
+ * |Platform | Value                                    | Example                                  |
+ * | ------- | ---------------------------------------- | ---------------------------------------- |
+ * | Linux   | `$XDG_DATA_HOME` or `$HOME`/.local/share | /home/alice/.local/share                 |
+ * | macOS   | `$HOME`/Library/Application Support      | /Users/Alice/Library/Application Support |
+ * | Windows | `{FOLDERID_RoamingAppData}`              | C:\Users\Alice\AppData\Roaming           |
+ *
+ * "data_local"
+ * |Platform | Value                                    | Example                                  |
+ * | ------- | ---------------------------------------- | ---------------------------------------- |
+ * | Linux   | `$XDG_DATA_HOME` or `$HOME`/.local/share | /home/alice/.local/share                 |
+ * | macOS   | `$HOME`/Library/Application Support      | /Users/Alice/Library/Application Support |
+ * | Windows | `{FOLDERID_LocalAppData}`                | C:\Users\Alice\AppData\Local             |
+ *
+ * "audio"
+ * |Platform | Value              | Example              |
+ * | ------- | ------------------ | -------------------- |
+ * | Linux   | `XDG_MUSIC_DIR`    | /home/alice/Music    |
+ * | macOS   | `$HOME`/Music      | /Users/Alice/Music   |
+ * | Windows | `{FOLDERID_Music}` | C:\Users\Alice\Music |
+ *
+ * "desktop"
+ * |Platform | Value                | Example                |
+ * | ------- | -------------------- | ---------------------- |
+ * | Linux   | `XDG_DESKTOP_DIR`    | /home/alice/Desktop    |
+ * | macOS   | `$HOME`/Desktop      | /Users/Alice/Desktop   |
+ * | Windows | `{FOLDERID_Desktop}` | C:\Users\Alice\Desktop |
+ *
+ * "document"
+ * |Platform | Value                  | Example                  |
+ * | ------- | ---------------------- | ------------------------ |
+ * | Linux   | `XDG_DOCUMENTS_DIR`    | /home/alice/Documents    |
+ * | macOS   | `$HOME`/Documents      | /Users/Alice/Documents   |
+ * | Windows | `{FOLDERID_Documents}` | C:\Users\Alice\Documents |
+ *
+ * "download"
+ * |Platform | Value                  | Example                  |
+ * | ------- | ---------------------- | ------------------------ |
+ * | Linux   | `XDG_DOWNLOAD_DIR`     | /home/alice/Downloads    |
+ * | macOS   | `$HOME`/Downloads      | /Users/Alice/Downloads   |
+ * | Windows | `{FOLDERID_Downloads}` | C:\Users\Alice\Downloads |
+ *
+ * "font"
+ * |Platform | Value                                                | Example                        |
+ * | ------- | ---------------------------------------------------- | ------------------------------ |
+ * | Linux   | `$XDG_DATA_HOME`/fonts or `$HOME`/.local/share/fonts | /home/alice/.local/share/fonts |
+ * | macOS   | `$HOME/Library/Fonts`                                | /Users/Alice/Library/Fonts     |
+ * | Windows | –                                                    | –                              |
+ *
+ * "picture"
+ * |Platform | Value                 | Example                 |
+ * | ------- | --------------------- | ----------------------- |
+ * | Linux   | `XDG_PICTURES_DIR`    | /home/alice/Pictures    |
+ * | macOS   | `$HOME`/Pictures      | /Users/Alice/Pictures   |
+ * | Windows | `{FOLDERID_Pictures}` | C:\Users\Alice\Pictures |
+ *
+ * "public"
+ * |Platform | Value                 | Example             |
+ * | ------- | --------------------- | ------------------- |
+ * | Linux   | `XDG_PUBLICSHARE_DIR` | /home/alice/Public  |
+ * | macOS   | `$HOME`/Public        | /Users/Alice/Public |
+ * | Windows | `{FOLDERID_Public}`   | C:\Users\Public     |
+ *
+ * "template"
+ * |Platform | Value                  | Example                                                    |
+ * | ------- | ---------------------- | ---------------------------------------------------------- |
+ * | Linux   | `XDG_TEMPLATES_DIR`    | /home/alice/Templates                                      |
+ * | macOS   | –                      | –                                                          |
+ * | Windows | `{FOLDERID_Templates}` | C:\Users\Alice\AppData\Roaming\Microsoft\Windows\Templates |
+ *
+ * "tmp"
+ *
+ * |Platform | Value                  | Example                                                    |
+ * | ------- | ---------------------- | ---------------------------------------------------------- |
+ * | Linux   | `TMPDIR`               | /tmp                                                       |
+ * | macOS   | `TMPDIR`               | /tmp                                                       |
+ * | Windows | `{TMP}`                | C:\Users\Alice\AppData\Local\Temp                          |
+ *
+ * "video"
+ * |Platform | Value               | Example               |
+ * | ------- | ------------------- | --------------------- |
+ * | Linux   | `XDG_VIDEOS_DIR`    | /home/alice/Videos    |
+ * | macOS   | `$HOME`/Movies      | /Users/Alice/Movies   |
+ * | Windows | `{FOLDERID_Videos}` | C:\Users\Alice\Videos |
+ */
+export function dir(kind: DirKind): string | null {
+  try {
+    return sendSync("op_get_dir", { kind });
+  } catch (error) {
+    if (error instanceof errors.PermissionDenied) {
+      throw error;
+    }
+    return null;
+  }
+}
+
+/**
+ * Returns the path to the current deno executable.
+ * Requires the `--allow-env` flag.
+ */
+export function execPath(): string {
+  return sendSync("op_exec_path");
+}
diff --git a/cli/js/ops/repl.ts b/cli/js/ops/repl.ts
new file mode 100644
index 000000000..3f40f4456
--- /dev/null
+++ b/cli/js/ops/repl.ts
@@ -0,0 +1,11 @@
+// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
+
+import { sendSync, sendAsync } from "./dispatch_json.ts";
+
+export function startRepl(historyFile: string): number {
+  return sendSync("op_repl_start", { historyFile });
+}
+
+export async function readline(rid: number, prompt: string): Promise<string> {
+  return sendAsync("op_repl_readline", { rid, prompt });
+}
diff --git a/cli/js/ops/resources.ts b/cli/js/ops/resources.ts
new file mode 100644
index 000000000..b04810989
--- /dev/null
+++ b/cli/js/ops/resources.ts
@@ -0,0 +1,23 @@
+// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
+import { sendSync } from "./dispatch_json.ts";
+
+export interface ResourceMap {
+  [rid: number]: string;
+}
+
+/** Returns a map of open _file like_ resource ids along with their string
+ * representation.
+ */
+export function resources(): ResourceMap {
+  const res = sendSync("op_resources") as Array<[number, string]>;
+  const resources: ResourceMap = {};
+  for (const resourceTuple of res) {
+    resources[resourceTuple[0]] = resourceTuple[1];
+  }
+  return resources;
+}
+
+/** Close the given resource ID. */
+export function close(rid: number): void {
+  sendSync("op_close", { rid });
+}
diff --git a/cli/js/ops/runtime.ts b/cli/js/ops/runtime.ts
new file mode 100644
index 000000000..7538ce12f
--- /dev/null
+++ b/cli/js/ops/runtime.ts
@@ -0,0 +1,67 @@
+// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
+
+import { sendSync } from "./dispatch_json.ts";
+
+// TODO(bartlomieju): these two types are duplicated
+// in `cli/js/build.ts` - deduplicate
+export type OperatingSystem = "mac" | "win" | "linux";
+export type Arch = "x64" | "arm64";
+
+export interface Start {
+  cwd: string;
+  pid: number;
+  args: string[];
+  location: string; // Absolute URL.
+  repl: boolean;
+  debugFlag: boolean;
+  depsFlag: boolean;
+  typesFlag: boolean;
+  versionFlag: boolean;
+  denoVersion: string;
+  v8Version: string;
+  tsVersion: string;
+  noColor: boolean;
+  os: OperatingSystem;
+  arch: Arch;
+}
+
+export function start(): Start {
+  return sendSync("op_start");
+}
+
+export interface Metrics {
+  opsDispatched: number;
+  opsDispatchedSync: number;
+  opsDispatchedAsync: number;
+  opsDispatchedAsyncUnref: number;
+  opsCompleted: number;
+  opsCompletedSync: number;
+  opsCompletedAsync: number;
+  opsCompletedAsyncUnref: number;
+  bytesSentControl: number;
+  bytesSentData: number;
+  bytesReceived: number;
+}
+
+/** Receive metrics from the privileged side of Deno.
+ *
+ *      > console.table(Deno.metrics())
+ *      ┌─────────────────────────┬────────┐
+ *      │         (index)         │ Values │
+ *      ├─────────────────────────┼────────┤
+ *      │      opsDispatched      │   3    │
+ *      │    opsDispatchedSync    │   2    │
+ *      │   opsDispatchedAsync    │   1    │
+ *      │ opsDispatchedAsyncUnref │   0    │
+ *      │      opsCompleted       │   3    │
+ *      │    opsCompletedSync     │   2    │
+ *      │    opsCompletedAsync    │   1    │
+ *      │ opsCompletedAsyncUnref  │   0    │
+ *      │    bytesSentControl     │   73   │
+ *      │      bytesSentData      │   0    │
+ *      │      bytesReceived      │  375   │
+ *      └─────────────────────────┴────────┘
+ */
+export function metrics(): Metrics {
+  return sendSync("op_metrics");
+}
diff --git a/cli/js/ops/runtime_compiler.ts b/cli/js/ops/runtime_compiler.ts
new file mode 100644
index 000000000..035a4ef59
--- /dev/null
+++ b/cli/js/ops/runtime_compiler.ts
@@ -0,0 +1,23 @@
+// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
+
+import { sendAsync } from "./dispatch_json.ts";
+
+interface CompileRequest {
+  rootName: string;
+  sources?: Record<string, string>;
+  options?: string;
+  bundle: boolean;
+}
+
+export async function compile(request: CompileRequest): Promise<string> {
+  return sendAsync("op_compile", request);
+}
+
+interface TranspileRequest {
+  sources: Record<string, string>;
+  options?: string;
+}
+
+export async function transpile(request: TranspileRequest): Promise<string> {
+  return sendAsync("op_transpile", request);
+}
diff --git a/cli/js/ops/tty.ts b/cli/js/ops/tty.ts
new file mode 100644
index 000000000..2ad44d025
--- /dev/null
+++ b/cli/js/ops/tty.ts
@@ -0,0 +1,14 @@
+import { sendSync } from "./dispatch_json.ts";
+
+/** Check if a given resource is TTY. */
+export function isatty(rid: number): boolean {
+  return sendSync("op_isatty", { rid });
+}
+
+/** Set TTY to be under raw mode or not. */
+export function setRaw(rid: number, mode: boolean): void {
+  sendSync("op_set_raw", {
+    rid,
+    mode
+  });
+}