module: add sourceURL magic comment hinting generated source

Source map is not necessary in strip-only mode. However, to map the
source file in debuggers to the original TypeScript source, add a
sourceURL magic comment to hint that it is a generated source.

PR-URL: #54402
Reviewed-By: Antoine du Hamel <[email protected]>
Reviewed-By: Kohei Ueno <[email protected]>
Reviewed-By: Marco Ippolito <[email protected]>
Reviewed-By: Matteo Collina <[email protected]>

lib/internal/modules/helpers.js

@@ -371,7 +371,10 @@ function stripTypeScriptTypes(source, filename) {
     const base64SourceMap = Buffer.from(map).toString('base64');
     return `${code}\n\n//# sourceMappingURL=data:application/json;base64,${base64SourceMap}`;
   }
-  return code;
+  // Source map is not necessary in strip-only mode. However, to map the source
+  // file in debuggers to the original TypeScript source, add a sourceURL magic
+  // comment to hint that it is a generated source.
+  return `${code}\n\n//# sourceURL=${filename}`;
 }
 
 function isUnderNodeModules(filename) {

test/common/inspector-helper.js

@@ -271,6 +271,14 @@ class InspectorSession {
         `break on ${url}:${line}`);
   }
 
+  waitForPauseOnStart() {
+    return this
+      .waitForNotification(
+        (notification) =>
+          notification.method === 'Debugger.paused' && notification.params.reason === 'Break on start',
+        'break on start');
+  }
+
   pausedDetails() {
     return this._pausedDetails;
   }

test/parallel/test-inspector-strip-types.js

@@ -0,0 +1,43 @@
+'use strict';
+
+const common = require('../common');
+common.skipIfInspectorDisabled();
+if (!process.config.variables.node_use_amaro) common.skip('Requires Amaro');
+
+const { NodeInstance } = require('../common/inspector-helper.js');
+const fixtures = require('../common/fixtures');
+const assert = require('assert');
+
+const scriptPath = fixtures.path('typescript/ts/test-typescript.ts');
+
+async function runTest() {
+  const child = new NodeInstance(
+    ['--inspect-brk=0', '--experimental-strip-types'],
+    undefined,
+    scriptPath);
+
+  const session = await child.connectInspectorSession();
+
+  const commands = [
+    { 'method': 'Debugger.enable' },
+    { 'method': 'Runtime.enable' },
+    { 'method': 'Runtime.runIfWaitingForDebugger' },
+  ];
+
+  await session.send(commands);
+
+  const scriptParsed = await session.waitForNotification((notification) => {
+    if (notification.method !== 'Debugger.scriptParsed') return false;
+
+    return notification.params.url === scriptPath;
+  });
+  // Verify that the script has a sourceURL, hinting that it is a generated source.
+  assert(scriptParsed.params.hasSourceURL);
+
+  await session.waitForPauseOnStart();
+  await session.runToCompletion();
+
+  assert.strictEqual((await child.expectShutdown()).exitCode, 0);
+}
+
+runTest().then(common.mustCall());