worker: use copy of process.env

Instead of sharing the OS-backed store for all `process.env` instances,
create a copy of `process.env` for every worker that is created.

The copies do not interact. Native-addons do not see modifications to
`process.env` from Worker threads, but child processes started from
Workers do default to the Worker’s copy of `process.env`.

This makes Workers behave like child processes as far as `process.env`
is concerned, and an option corresponding to the `child_process`
module’s `env` option is added to the constructor.

Fixes: https://github.com/nodejs/node/issues/24947

PR-URL: https://github.com/nodejs/node/pull/26544
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Vse Mozhet Byt <vsemozhetbyt@gmail.com>
Reviewed-By: Yongsheng Zhang <zyszys98@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>

2 files changed, 26 insertions, 0 deletions

diff --git a/lib/internal/worker.js b/lib/internal/worker.js
index 02f6661b54..c0a2baa869 100644
--- a/lib/internal/worker.js
+++ b/lib/internal/worker.js
@@ -45,6 +45,8 @@ const kOnCouldNotSerializeErr = Symbol('kOnCouldNotSerializeErr');
 const kOnErrorMessage = Symbol('kOnErrorMessage');
 const kParentSideStdio = Symbol('kParentSideStdio');
 
+const SHARE_ENV = Symbol.for('nodejs.worker_threads.SHARE_ENV');
+
 let debuglog;
 function debug(...args) {
   if (!debuglog) {
@@ -79,12 +81,33 @@ class Worker extends EventEmitter {
       }
     }
 
+    let env;
+    if (typeof options.env === 'object' && options.env !== null) {
+      env = Object.create(null);
+      for (const [ key, value ] of Object.entries(options.env))
+        env[key] = `${value}`;
+    } else if (options.env == null) {
+      env = process.env;
+    } else if (options.env !== SHARE_ENV) {
+      throw new ERR_INVALID_ARG_TYPE(
+        'options.env',
+        ['object', 'undefined', 'null', 'worker_threads.SHARE_ENV'],
+        options.env);
+    }
+
     const url = options.eval ? null : pathToFileURL(filename);
     // Set up the C++ handle for the worker, as well as some internal wiring.
     this[kHandle] = new WorkerImpl(url, options.execArgv);
     if (this[kHandle].invalidExecArgv) {
       throw new ERR_WORKER_INVALID_EXEC_ARGV(this[kHandle].invalidExecArgv);
     }
+    if (env === process.env) {
+      // This may be faster than manually cloning the object in C++, especially
+      // when recursively spawning Workers.
+      this[kHandle].cloneParentEnvVars();
+    } else if (env !== undefined) {
+      this[kHandle].setEnvVars(env);
+    }
     this[kHandle].onexit = (code) => this[kOnExit](code);
     this[kPort] = this[kHandle].messagePort;
     this[kPort].on('message', (data) => this[kOnMessage](data));
@@ -253,6 +276,7 @@ function pipeWithoutWarning(source, dest) {
 module.exports = {
   ownsProcessState,
   isMainThread,
+  SHARE_ENV,
   threadId,
   Worker,
 };
diff --git a/lib/worker_threads.js b/lib/worker_threads.js
index 722e47caf1..01d01e2a33 100644
--- a/lib/worker_threads.js
+++ b/lib/worker_threads.js
@@ -2,6 +2,7 @@
 
 const {
   isMainThread,
+  SHARE_ENV,
   threadId,
   Worker
 } = require('internal/worker');
@@ -18,6 +19,7 @@ module.exports = {
   MessageChannel,
   moveMessagePortToContext,
   threadId,
+  SHARE_ENV,
   Worker,
   parentPort: null,
   workerData: null,