process: handle process.env.NODE_V8_COVERAGE in pre-execution

Since this depends on environment variable, and the worker threads
do not need to persist the variable value because they cannot
switch cwd.

PR-URL: #26466
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>

lib/internal/bootstrap/node.js

@@ -317,29 +317,6 @@ Object.defineProperty(process, 'features', {
     hasUncaughtExceptionCaptureCallback;
 }
 
-// User-facing NODE_V8_COVERAGE environment variable that writes
-// ScriptCoverage to a specified file.
-if (process.env.NODE_V8_COVERAGE) {
-  const originalReallyExit = process.reallyExit;
-  const cwd = NativeModule.require('internal/process/execution').tryGetCwd();
-  const { resolve } = NativeModule.require('path');
-  // Resolve the coverage directory to an absolute path, and
-  // overwrite process.env so that the original path gets passed
-  // to child processes even when they switch cwd.
-  const coverageDirectory = resolve(cwd, process.env.NODE_V8_COVERAGE);
-  process.env.NODE_V8_COVERAGE = coverageDirectory;
-  const {
-    writeCoverage,
-    setCoverageDirectory
-  } = NativeModule.require('internal/coverage-gen/with_profiler');
-  setCoverageDirectory(coverageDirectory);
-  process.on('exit', writeCoverage);
-  process.reallyExit = (code) => {
-    writeCoverage();
-    originalReallyExit(code);
-  };
-}
-
 function setupProcessObject() {
   const EventEmitter = NativeModule.require('events');
   const origProcProto = Object.getPrototypeOf(process);

lib/internal/bootstrap/pre_execution.js

@@ -10,6 +10,14 @@ function prepareMainThreadExecution() {
 
   setupWarningHandler();
 
+  // Resolve the coverage directory to an absolute path, and
+  // overwrite process.env so that the original path gets passed
+  // to child processes even when they switch cwd.
+  if (process.env.NODE_V8_COVERAGE) {
+    process.env.NODE_V8_COVERAGE =
+      setupCoverageHooks(process.env.NODE_V8_COVERAGE);
+  }
+
   // Only main thread receives signals.
   setupSignalHandlers();
 
@@ -47,6 +55,26 @@ function setupWarningHandler() {
   }
 }
 
+// Setup User-facing NODE_V8_COVERAGE environment variable that writes
+// ScriptCoverage to a specified file.
+function setupCoverageHooks(dir) {
+  const originalReallyExit = process.reallyExit;
+  const cwd = require('internal/process/execution').tryGetCwd();
+  const { resolve } = require('path');
+  const coverageDirectory = resolve(cwd, dir);
+  const {
+    writeCoverage,
+    setCoverageDirectory
+  } = require('internal/coverage-gen/with_profiler');
+  setCoverageDirectory(coverageDirectory);
+  process.on('exit', writeCoverage);
+  process.reallyExit = (code) => {
+    writeCoverage();
+    originalReallyExit(code);
+  };
+  return coverageDirectory;
+}
+
 function initializeReport() {
   if (!getOptionValue('--experimental-report')) {
     return;
@@ -262,6 +290,7 @@ function loadPreloadModules() {
 }
 
 module.exports = {
+  setupCoverageHooks,
   setupWarningHandler,
   prepareMainThreadExecution,
   initializeDeprecations,

lib/internal/main/worker_thread.js

@@ -4,6 +4,7 @@
 // message port.
 
 const {
+  setupCoverageHooks,
   setupWarningHandler,
   initializeDeprecations,
   initializeESMLoader,
@@ -42,6 +43,12 @@ const debug = require('util').debuglog('worker');
 
 setupWarningHandler();
 
+// Since worker threads cannot switch cwd, we do not need to
+// overwrite the process.env.NODE_V8_COVERAGE variable.
+if (process.env.NODE_V8_COVERAGE) {
+  setupCoverageHooks(process.env.NODE_V8_COVERAGE);
+}
+
 debug(`[${threadId}] is setting up worker child environment`);
 
 // Set up the message port and start listening