From e8ad93bf08edff5c54ccd9b8370ac433fda0bf57 Mon Sep 17 00:00:00 2001
From: Anna Henningsen <anna@addaleax.net>
Date: Tue, 18 Sep 2018 13:12:17 +0200
Subject: [PATCH] worker,coverage: support V8 coverage generation

---
 lib/internal/process/coverage.js    |  8 ++++----
 test/fixtures/v8-coverage/worker.js |  5 +++++
 test/parallel/test-v8-coverage.js   | 17 +++++++++++++++++
 3 files changed, 26 insertions(+), 4 deletions(-)
 create mode 100644 test/fixtures/v8-coverage/worker.js

diff --git a/lib/internal/process/coverage.js b/lib/internal/process/coverage.js
index c2349d4ce0e24e..df45285baaee02 100644
--- a/lib/internal/process/coverage.js
+++ b/lib/internal/process/coverage.js
@@ -1,9 +1,7 @@
 'use strict';
 const path = require('path');
 const { mkdirSync, writeFileSync } = require('fs');
-// TODO(addaleax): add support for coverage to worker threads.
-const hasInspector = process.config.variables.v8_enable_inspector === 1 &&
-  require('internal/worker').isMainThread;
+const hasInspector = process.config.variables.v8_enable_inspector === 1;
 let inspector = null;
 if (hasInspector) inspector = require('inspector');
 
@@ -14,7 +12,9 @@ function writeCoverage() {
     return;
   }
 
-  const filename = `coverage-${process.pid}-${Date.now()}.json`;
+  const { threadId } = require('internal/worker');
+
+  const filename = `coverage-${process.pid}-${Date.now()}-${threadId}.json`;
   try {
     // TODO(bcoe): switch to mkdirp once #22302 is addressed.
     mkdirSync(process.env.NODE_V8_COVERAGE);
diff --git a/test/fixtures/v8-coverage/worker.js b/test/fixtures/v8-coverage/worker.js
new file mode 100644
index 00000000000000..901794e97ac8ab
--- /dev/null
+++ b/test/fixtures/v8-coverage/worker.js
@@ -0,0 +1,5 @@
+'use strict';
+const { Worker } = require('worker_threads');
+const path = require('path');
+
+new Worker(path.resolve(__dirname, 'subprocess.js'));
diff --git a/test/parallel/test-v8-coverage.js b/test/parallel/test-v8-coverage.js
index 91581a5a073460..16a55b0fc4b8e8 100644
--- a/test/parallel/test-v8-coverage.js
+++ b/test/parallel/test-v8-coverage.js
@@ -79,6 +79,23 @@ function nextdir() {
   assert.strictEqual(fixtureCoverage.functions[2].ranges[1].count, 0);
 }
 
+// outputs coverage from worker.
+{
+  const coverageDirectory = path.join(tmpdir.path, nextdir());
+  const output = spawnSync(process.execPath, [
+    '--experimental-worker',
+    require.resolve('../fixtures/v8-coverage/worker')
+  ], { env: { ...process.env, NODE_V8_COVERAGE: coverageDirectory } });
+  assert.strictEqual(output.status, 0);
+  const fixtureCoverage = getFixtureCoverage('subprocess.js',
+                                             coverageDirectory);
+  assert.ok(fixtureCoverage);
+  // first branch executed.
+  assert.strictEqual(fixtureCoverage.functions[2].ranges[0].count, 1);
+  // second branch did not execute.
+  assert.strictEqual(fixtureCoverage.functions[2].ranges[1].count, 0);
+}
+
 // does not output coverage if NODE_V8_COVERAGE is empty.
 {
   const coverageDirectory = path.join(tmpdir.path, nextdir());