Support --inspect-brk

Author: GeoffreyBooth

lib/internal/modules/esm/loader.js

@@ -382,7 +382,12 @@ class ModuleLoader {
     return onImport.traceSync(() => {
       const request = { specifier: url, phase: kEvaluationPhase, attributes: kEmptyObject, __proto__: null };
       const job = this.getOrCreateModuleJob(undefined, request, kImportInImportedESM);
-      job.module.instantiate();
+      if (getOptionValue('--inspect-brk')) {
+        const { callAndPauseOnStart } = internalBinding('inspector');
+        callAndPauseOnStart(job.module.instantiate, job.module);
+      } else {
+        job.module.instantiate();
+      }
       if (job.module.hasAsyncGraph) {
         return { __proto__: null, module: job.module, completed: false };
       }

lib/internal/modules/run_main.js

@@ -157,10 +157,9 @@ function executeUserEntryPoint(main = process.argv[1]) {
     const mainPath = resolvedMain || main;
     const mainURL = getOptionValue('--entry-url') ? new URL(mainPath, getCWDURL()) : pathToFileURL(mainPath);
 
-    // When no async hooks or --inspect-brk are needed, try the fully synchronous path first.
+    // When no async hooks are needed, try the fully synchronous path first.
     // This avoids creating any promises during startup.
-    if (!getOptionValue('--inspect-brk') &&
-        getOptionValue('--experimental-loader').length === 0 &&
+    if (getOptionValue('--experimental-loader').length === 0 &&
         getOptionValue('--import').length === 0) {
       const cascadedLoader = require('internal/modules/esm/loader').getOrInitializeCascadedLoader();
       const { module: entryModule, completed } = cascadedLoader.importSyncForEntryPoint(mainURL.href);

test/parallel/test-inspector-debug-brk-flag-esm.js

@@ -0,0 +1,45 @@
+'use strict';
+const common = require('../common');
+
+// Test that --inspect-brk pauses at the first line of an ESM entry point.
+
+common.skipIfInspectorDisabled();
+
+const assert = require('assert');
+const fixtures = require('../common/fixtures');
+const { NodeInstance } = require('../common/inspector-helper.js');
+
+async function testBreakpointOnStart(session) {
+  const commands = [
+    { 'method': 'Runtime.enable' },
+    { 'method': 'Debugger.enable' },
+    { 'method': 'Debugger.setPauseOnExceptions',
+      'params': { 'state': 'none' } },
+    { 'method': 'Debugger.setAsyncCallStackDepth',
+      'params': { 'maxDepth': 0 } },
+    { 'method': 'Profiler.enable' },
+    { 'method': 'Profiler.setSamplingInterval',
+      'params': { 'interval': 100 } },
+    { 'method': 'Debugger.setBlackboxPatterns',
+      'params': { 'patterns': [] } },
+    { 'method': 'Runtime.runIfWaitingForDebugger' },
+  ];
+
+  await session.send({ method: 'NodeRuntime.enable' });
+  await session.waitForNotification('NodeRuntime.waitingForDebugger');
+  await session.send(commands);
+  await session.send({ method: 'NodeRuntime.disable' });
+  await session.waitForBreakOnLine(0, session.scriptURL());
+}
+
+async function runTests() {
+  const child = new NodeInstance(['--inspect-brk=0'], '', fixtures.path('es-modules', 'loop.mjs'));
+  const session = await child.connectInspectorSession();
+
+  await testBreakpointOnStart(session);
+  await session.runToCompletion();
+
+  assert.strictEqual((await child.expectShutdown()).exitCode, 55);
+}
+
+runTests().then(common.mustCall());