feat: option to disable source maps (#2628)

allowing to disable DevTools source maps similar to what DevTools
settings allow in the UI.

docs/configuration.md

@@ -180,6 +180,11 @@ The Chrome DevTools MCP server supports the following configuration option:
   - **Type:** boolean
   - **Default:** `true`
 
+- **`--sourceMaps`/ `--source-maps`**
+  Whether to enable source maps in DevTools. Use --no-source-maps to disable.
+  - **Type:** boolean
+  - **Default:** `true`
+
 - **`--screenshotFormat`/ `--screenshot-format`**
   Override the default output format used by take_screenshot when the caller does not specify one. JPEG and WebP are ~3-5x smaller than PNG, which reduces transfer and storage size. To reduce context size use --screenshotMaxWidth / --screenshotMaxHeight, since image tokens scale with dimensions rather than encoded bytes. Unset preserves the existing default ("png").
   - **Type:** string

src/McpContext.ts

@@ -58,6 +58,8 @@ interface McpContextOptions {
   experimentalIncludeAllPages?: boolean;
   // Whether CrUX data should be fetched.
   performanceCrux: boolean;
+  // Whether source maps are enabled in DevTools.
+  sourceMaps?: boolean;
   // The allow list of URL patterns to allow loading resources.
   allowList?: string[];
   // The block list of URL patterns to block loading resources.
@@ -567,6 +569,7 @@ export class McpContext implements Context {
           page.browserContext(),
         ),
         navigationTimeout: this.#options.navigationTimeout,
+        sourceMaps: this.#options.sourceMaps,
       });
       this.#mcpPages.set(page, mcpPage);
       await mcpPage.init();

src/McpPage.ts

@@ -138,6 +138,7 @@ export class McpPage implements ContextPage {
   #hasNetworkBlockOrAllowlist: boolean;
   #locatorClass: typeof Locator;
   #navigationTimeout: number;
+  #sourceMaps: boolean;
 
   constructor(
     page: Page,
@@ -147,11 +148,13 @@ export class McpPage implements ContextPage {
       locatorClass: typeof Locator;
       isolatedContextName?: string;
       navigationTimeout?: number;
+      sourceMaps?: boolean;
     },
   ) {
     this.#hasNetworkBlockOrAllowlist = options.hasNetworkBlockOrAllowlist;
     this.#locatorClass = options.locatorClass;
     this.#navigationTimeout = options.navigationTimeout ?? NAVIGATION_TIMEOUT;
+    this.#sourceMaps = options.sourceMaps ?? true;
     this.pptrPage = page;
     this.id = id;
     this.isolatedContextName = options.isolatedContextName;
@@ -196,7 +199,9 @@ export class McpPage implements ContextPage {
     }
     try {
       const session = await this.pptrPage.createCDPSession();
-      this.#devtoolsUniverse = await createTargetUniverse(session);
+      this.#devtoolsUniverse = await createTargetUniverse(session, {
+        sourceMaps: this.#sourceMaps,
+      });
     } catch (e) {
       logger?.('Failed to initialize DevTools universe', e);
     }

src/config/mcp-options.ts

@@ -269,6 +269,12 @@ export const mcpOptions = {
     describe:
       'Set to false to disable JavaScript execution. When disabled, evaluation tools (evaluate_script and slim evaluate) are disabled, the initScript parameter in navigate_page is turned off, and navigating to javascript:, data:, or vbscript: URLs is disallowed.',
   },
+  sourceMaps: {
+    type: 'boolean',
+    default: true,
+    describe:
+      'Whether to enable source maps in DevTools. Use --no-source-maps to disable.',
+  },
   clearcutEndpoint: {
     type: 'string',
     hidden: true,
@@ -535,6 +541,7 @@ export function parser(
         '$0 --no-performance-crux',
         'Disable CrUX (field data) integration in performance tools.',
       ],
+      ['$0 --no-source-maps', 'Disable source maps in DevTools.'],
       [
         '$0 --no-javascript-evaluation',
         'Disable JavaScript execution (disables evaluation tools, initScript in navigate_page, and navigating to javascript:, data:, or vbscript: URLs).',

src/devtools/DevtoolsUtils.ts

@@ -137,8 +137,13 @@ export interface TargetUniverse {
   session: CDPSession;
 }
 
+export interface CreateTargetUniverseOptions {
+  sourceMaps?: boolean;
+}
+
 export async function createTargetUniverse(
   session: CDPSession,
+  options?: CreateTargetUniverseOptions,
 ): Promise<TargetUniverse> {
   const settingStorage = new DevTools.Common.Settings.SettingsStorage({});
   const universe = new DevTools.Foundation.Universe.Universe({
@@ -156,6 +161,17 @@ export async function createTargetUniverse(
     supportsEmulation: false,
   });
 
+  const sourceMaps = options?.sourceMaps ?? true;
+  const jsSourceMapsSetting = universe.settings.resolve(
+    DevTools.SDKSettings.jsSourceMapsEnabledSettingDescriptor,
+  );
+  jsSourceMapsSetting.set(sourceMaps);
+
+  const cssSourceMapsSetting = universe.settings.resolve(
+    DevTools.SDKSettings.cssSourceMapsEnabledSettingDescriptor,
+  );
+  cssSourceMapsSetting.set(sourceMaps);
+
   const setting = universe.settings.resolve(
     DevTools.SourceMapManager.lazyLoadingSettingDescriptor,
   );

src/index.ts

@@ -259,6 +259,7 @@ export class McpServer {
         experimentalIncludeAllPages:
           this.#serverArgs.experimentalIncludeAllPages,
         performanceCrux: this.#serverArgs.performanceCrux,
+        sourceMaps: this.#serverArgs.sourceMaps,
         allowList: allowlist,
         blocklist: blocklist,
         allowUnrestrictedPaths: this.#serverArgs.allowUnrestrictedPaths,

src/telemetry/flag_usage_metrics.json

@@ -437,5 +437,13 @@
   {
     "name": "category_memory",
     "flagType": "boolean"
+  },
+  {
+    "name": "source_maps_present",
+    "flagType": "boolean"
+  },
+  {
+    "name": "source_maps",
+    "flagType": "boolean"
   }
 ]

tests/cli.test.ts

@@ -38,6 +38,7 @@ describe('cli args parsing', () => {
     memoryDebugging: false,
     experimentalStructuredContent: false,
     pageIdRouting: true,
+    sourceMaps: true,
   };
 
   it('parses with default args', async () => {
@@ -415,4 +416,18 @@ describe('cli args parsing', () => {
       'https://b.com/*',
     ]);
   });
+
+  it('parses source-maps flag', async () => {
+    const defaultParsed = parseArguments(['main.js']);
+    assert.strictEqual(defaultParsed.sourceMaps, true);
+
+    const disabledArgs = parseArguments(['--no-source-maps']);
+    assert.strictEqual(disabledArgs.sourceMaps, false);
+
+    const explicitFalseArgs = parseArguments(['--source-maps=false']);
+    assert.strictEqual(explicitFalseArgs.sourceMaps, false);
+
+    const explicitTrueArgs = parseArguments(['--source-maps=true']);
+    assert.strictEqual(explicitTrueArgs.sourceMaps, true);
+  });
 });

tests/devtools/DevtoolsUtils.test.ts

@@ -152,6 +152,51 @@ describe('createTargetUniverse', () => {
       );
     });
   });
+
+  it('enables source maps by default', async () => {
+    await withBrowser(async (browser, page) => {
+      const targetUniverse = await createTargetUniverse(
+        await page.createCDPSession(),
+      );
+      assert.ok(targetUniverse);
+
+      assert.strictEqual(
+        targetUniverse.universe.settings
+          .resolve(DevTools.SDKSettings.jsSourceMapsEnabledSettingDescriptor)
+          .get(),
+        true,
+      );
+      assert.strictEqual(
+        targetUniverse.universe.settings
+          .resolve(DevTools.SDKSettings.cssSourceMapsEnabledSettingDescriptor)
+          .get(),
+        true,
+      );
+    });
+  });
+
+  it('disables source maps when sourceMaps is false', async () => {
+    await withBrowser(async (browser, page) => {
+      const targetUniverse = await createTargetUniverse(
+        await page.createCDPSession(),
+        {sourceMaps: false},
+      );
+      assert.ok(targetUniverse);
+
+      assert.strictEqual(
+        targetUniverse.universe.settings
+          .resolve(DevTools.SDKSettings.jsSourceMapsEnabledSettingDescriptor)
+          .get(),
+        false,
+      );
+      assert.strictEqual(
+        targetUniverse.universe.settings
+          .resolve(DevTools.SDKSettings.cssSourceMapsEnabledSettingDescriptor)
+          .get(),
+        false,
+      );
+    });
+  });
 });
 
 describe('SymbolizedError', () => {

tests/tools/console.test.ts

@@ -643,6 +643,39 @@ describe('console', () => {
       });
     });
 
+    it('does not apply source maps when sourceMaps is false', async () => {
+      server.addRoute('/main.min.js', (_req, res) => {
+        res.setHeader('Content-Type', 'text/javascript');
+        res.statusCode = 200;
+        res.end(`function n(){throw new Error("b00m!")}function o(){n()}(function n(){o()})();
+          //# sourceMappingURL=data:application/json;charset=utf-8;base64,eyJ2ZXJzaW9uIjozLCJuYW1lcyI6WyJiYXIiLCJFcnJvciIsImZvbyIsIklpZmUiXSwic291cmNlcyI6WyIuL21haW4uanMiXSwic291cmNlc0NvbnRlbnQiOlsiXG5mdW5jdGlvbiBiYXIoKSB7XG4gIHRocm93IG5ldyBFcnJvcignYjAwbSEnKTtcbn1cblxuZnVuY3Rpb24gZm9vKCkge1xuICBiYXIoKTtcbn1cblxuKGZ1bmN0aW9uIElpZmUoKSB7XG4gIGZvbygpO1xufSkoKTtcblxuIl0sIm1hcHBpbmdzIjoiQUFDQSxTQUFTQSxJQUNQLE1BQU0sSUFBSUMsTUFBTSxRQUNsQixDQUVBLFNBQVNDLElBQ1BGLEdBQ0YsRUFFQSxTQUFVRyxJQUNSRCxHQUNELEVBRkQiLCJpZ25vcmVMaXN0IjpbXX0=
+        `);
+      });
+      server.addHtmlRoute(
+        '/index.html',
+        `<script src="${server.getRoute('/main.min.js')}"></script>`,
+      );
+
+      await withMcpContext(
+        async (response, context) => {
+          const page = context.getSelectedMcpPage();
+          await page.pptrPage.goto(server.getRoute('/index.html'));
+
+          await getConsoleMessage.handler(
+            {params: {msgid: 1}, page: context.getSelectedMcpPage()},
+            response,
+            context,
+          );
+          const formattedResponse = await response.handle(context);
+          const rawText = getTextContent(formattedResponse.content[0]);
+
+          assert.ok(rawText.includes('main.min.js'));
+          assert.ok(!rawText.includes('main.js'));
+        },
+        {sourceMaps: false},
+      );
+    });
+
     it('ignores frames from ignore listed URLs', async t => {
       server.addHtmlRoute(
         '/index.html',

tests/utils.ts

@@ -161,6 +161,7 @@ export async function withMcpContext(
     debug?: boolean;
     autoOpenDevTools?: boolean;
     performanceCrux?: boolean;
+    sourceMaps?: boolean;
     executablePath?: string;
     args?: string[];
     blockedUrlPattern?: string[];
@@ -183,6 +184,7 @@ export async function withMcpContext(
       {
         experimentalDevToolsDebugging: false,
         performanceCrux: options.performanceCrux ?? true,
+        sourceMaps: options.sourceMaps ?? true,
         allowList: options.allowedUrlPattern,
         blocklist: options.blockedUrlPattern,
         allowUnrestrictedPaths: options.allowUnrestrictedPaths ?? false,