Add WebChannel API for JS source code fetching

Implement browser communication to fetch JS source code using
GlobalJSSourceId. This enables the profiler to retrieve original
source content directly from the browser's JavaScript engine.

Backend bug: https://bugzilla.mozilla.org/show_bug.cgi?id=1916785

Author: canova

src/app-logic/browser-connection.ts

@@ -12,6 +12,7 @@ import {
   querySymbolicationApiViaWebChannel,
   getPageFaviconsViaWebChannel,
   showFunctionInDevtoolsViaWebChannel,
+  getJSSourcesViaWebChannel,
 } from './web-channel';
 import type {
   Milliseconds,
@@ -83,6 +84,8 @@ export interface BrowserConnection {
     line: number | null,
     column: number | null
   ): Promise<void>;
+
+  getJSSource(sourceUuid: string): Promise<string | null>;
 }
 
 /**
@@ -98,6 +101,7 @@ class BrowserConnectionImpl implements BrowserConnection {
   _webChannelSupportsGetExternalMarkers: boolean;
   _webChannelSupportsGetPageFavicons: boolean;
   _webChannelSupportsOpenDebuggerInTab: boolean;
+  _webChannelSupportsGetJSSource: boolean;
   _geckoProfiler: $GeckoProfiler | undefined;
 
   constructor(webChannelVersion: number) {
@@ -106,6 +110,7 @@ class BrowserConnectionImpl implements BrowserConnection {
     this._webChannelSupportsGetExternalMarkers = webChannelVersion >= 3;
     this._webChannelSupportsGetPageFavicons = webChannelVersion >= 4;
     this._webChannelSupportsOpenDebuggerInTab = webChannelVersion >= 5;
+    this._webChannelSupportsGetJSSource = webChannelVersion >= 6;
   }
 
   // Only called when we must obtain the profile from the browser, i.e. if we
@@ -226,6 +231,26 @@ class BrowserConnectionImpl implements BrowserConnection {
 
     return [];
   }
+
+  /**
+   * Fetches JavaScript source code from the browser using the source UUID.
+   * This method requires WebChannel version 6 or higher (Firefox 145+).
+   */
+  async getJSSource(sourceUuid: string): Promise<string | null> {
+    if (!this._webChannelSupportsGetJSSource) {
+      throw new Error(
+        "Can't use getJSSource in Firefox versions with the old WebChannel."
+      );
+    }
+
+    // Even though the WebChannel request for fetching JS sources supports
+    // fetching multiple sources, we only fetch one at a time currently.
+    // TODO: Change this to fetch multiple JS sources at the load time or while
+    // we share the profile.
+    return getJSSourcesViaWebChannel([sourceUuid]).then(
+      (sources) => sources[0]
+    );
+  }
 }
 
 // Should work with:

src/app-logic/web-channel.ts

@@ -28,7 +28,8 @@ export type Request =
   | GetSymbolTableRequest
   | QuerySymbolicationApiRequest
   | GetPageFaviconsRequest
-  | OpenScriptInTabDebuggerRequest;
+  | OpenScriptInTabDebuggerRequest
+  | GetJSSourcesRequest;
 
 type StatusQueryRequest = { type: 'STATUS_QUERY' };
 type EnableMenuButtonRequest = { type: 'ENABLE_MENU_BUTTON' };
@@ -64,6 +65,10 @@ type OpenScriptInTabDebuggerRequest = {
   line: number | null;
   column: number | null;
 };
+type GetJSSourcesRequest = {
+  type: 'GET_JS_SOURCES';
+  sourceUuids: Array<string>;
+};
 
 export type MessageFromBrowser<R extends ResponseFromBrowser> =
   | OutOfBandErrorMessageFromBrowser
@@ -128,6 +133,10 @@ type StatusQueryResponse = {
   //  Shipped in Firefox 136.
   //  Adds support for showing the JS script in DevTools debugger.
   //    - OPEN_SCRIPT_IN_DEBUGGER
+  // Version 6:
+  //  Shipped in Firefox 145.
+  //  Adds support for fetching JS sources.
+  //    - GET_JS_SOURCES
   version?: number;
 };
 type EnableMenuButtonResponse = void;
@@ -138,6 +147,7 @@ type GetSymbolTableResponse = SymbolTableAsTuple;
 type QuerySymbolicationApiResponse = string;
 type GetPageFaviconsResponse = Array<FaviconData | null>;
 type OpenScriptInTabDebuggerResponse = void;
+type GetJSSourcesResponse = Array<string | null>;
 
 // TypeScript function overloads for request/response pairs.
 function _sendMessageWithResponse(
@@ -167,6 +177,10 @@ function _sendMessageWithResponse(
 function _sendMessageWithResponse(
   request: OpenScriptInTabDebuggerRequest
 ): Promise<OpenScriptInTabDebuggerResponse>;
+function _sendMessageWithResponse(
+  request: GetJSSourcesRequest
+): Promise<GetJSSourcesResponse>;
+
 function _sendMessageWithResponse(request: Request): Promise<any> {
   const requestId = _requestId++;
   const type = request.type;
@@ -371,6 +385,15 @@ export async function showFunctionInDevtoolsViaWebChannel(
   });
 }
 
+export async function getJSSourcesViaWebChannel(
+  sourceUuids: Array<string>
+): Promise<Array<string | null>> {
+  return _sendMessageWithResponse({
+    type: 'GET_JS_SOURCES',
+    sourceUuids,
+  });
+}
+
 /**
  * -----------------------------------------------------------------------------
  *

src/test/unit/query-api.test.ts

@@ -271,6 +271,7 @@ describe('RegularExternalCommunicationDelegate', function () {
             getSymbolTable: jest.fn(bcOverrides.getSymbolTable),
             getPageFavicons: jest.fn(bcOverrides.getPageFavicons),
             showFunctionInDevtools: jest.fn(bcOverrides.showFunctionInDevtools),
+            getJSSource: jest.fn(bcOverrides.getJSSource),
           }
         : null;