Fix deadlock caused by `import 'vscode'` from modules loaded via `require(esm)` #285417

mizdra · 2025-12-30T12:27:10Z

Background

An extension with code like the following will cause a deadlock.

// src/extension.cjs
const vscode = require('vscode');
require('./sub.js');
exports.activate = function (context) {
  // ...
};

// src/sub.js
// The following will hang the test.
import * as vscode from 'vscode';

The detailed reasons are explained at #285297 (comment). This PR attempts to fix that issue using module.registerHooks.

How to test

The test for https://github.com/mizdra/repro-vscode-test-hang can run to completion without hanging.

$ gh pr checkout 285417

$ # Build vscode
$ npm install

$ git clone git@github.com:mizdra/repro-vscode-test-hang.git
$ cd repro-vscode-test-hang

$ # Edit files...
$ vim
$ git diff -U1                 
diff --git a/test/runTest.js b/test/runTest.js
index 01ac63b..99c3376 100644
--- a/test/runTest.js
+++ b/test/runTest.js
@@ -14,3 +14,3 @@ async function main() {
       launchArgs: ['--disable-extensions'],
-      // vscodeExecutablePath: '/Users/mizdra/src/github.com/microsoft/vscode/scripts/code.sh',
+      vscodeExecutablePath: '/Users/mizdra/src/github.com/microsoft/vscode/scripts/code.sh',
     });

$ npm start

Protected by Socket Firewall

> repro-vscode-test-hang@1.0.0 start
> node test/runTest.js

npm warn Unknown project config "disturl". This will stop working in the next major version of npm.
npm warn Unknown project config "target". This will stop working in the next major version of npm.
npm warn Unknown project config "ms_build_id". This will stop working in the next major version of npm.
npm warn Unknown project config "runtime". This will stop working in the next major version of npm.
npm warn Unknown project config "build_from_source". This will stop working in the next major version of npm.
npm warn Unknown project config "timeout". This will stop working in the next major version of npm.

> code-oss-dev@1.108.0 electron
> node build/lib/electron.ts

[21:57:55] Synchronizing built-in extensions...
[21:57:55] You can manage built-in extensions with the --builtin flag
[21:57:55] [github] ms-vscode.js-debug-companion@1.1.3 ✔︎
[21:57:55] [github] ms-vscode.js-debug@1.105.0 ✔︎
[21:57:55] [github] ms-vscode.vscode-js-profile-table@1.0.10 ✔︎
[main 2025-12-30T12:57:55.974Z] [CSS_DEV] DONE, 283 css modules (52ms)
[main 2025-12-30T12:57:56.178Z] update#setState disabled
Started local extension host with pid 81065.
No default agent registered
AssertionError [ERR_ASSERTION]: Expected values to be strictly equal:

1 !== 2

	at file:///Users/mizdra/src/github.com/mizdra/repro-vscode-test-hang/test/index.test.js:6:8
...

…ptors

mizdra · 2025-12-30T13:19:12Z

src/vs/workbench/api/node/extHostExtensionService.ts

+		// Module loading tricks based on `module.registerHooks`.
+		// `module.registerHooks` is a generic interceptor that intercepts `require(...)`, `import ...`, and `import(...)`.
+		// However, at this time, `NodeModuleInterceptor` only intercepts `import 'vscode'` and `import('vscode')`.
+		// This can also intercept `require('vscode')`, but interception by `NodeModuleRequireInterceptor` takes precedence.


It's a bit confusing that only require('vscode') gets intercepted by NodeModuleRequireInterceptor. So I tried modifying it as follows to have require('vscode') intercepted by NodeModuleInterceptor.

--- a/src/vs/workbench/api/node/extHostExtensionService.ts +++ b/src/vs/workbench/api/node/extHostExtensionService.ts @@ -35,7 +35,7 @@ class NodeModuleRequireInterceptor extends RequireInterceptor { const originalLoad = node_module._load; node_module._load = function load(request: string, parent: { filename: string }, isMain: boolean) { request = applyAlternatives(request); - if (!that._factories.has(request)) { + if (!that._factories.has(request) || request === 'vscode') { return originalLoad.apply(this, arguments); }

However, this causes an ENAMETOOLONG error.

$ cd repro-vscode-test-hang $ # Edit files $ vim $ git diff diff --git a/test/index.test.js b/test/index.test.js index 209123b..3b8b882 100644 --- a/test/index.test.js +++ b/test/index.test.js @@ -1,6 +1,10 @@ import assert from 'node:assert/strict'; // The following will hang the test. -import * as vscode from 'vscode'; +// import * as vscode from 'vscode'; + +import { createRequire } from 'node:module'; +const require = createRequire(import.meta.url); +const vscode = require('vscode'); assert.equal(1, 2); diff --git a/test/runTest.js b/test/runTest.js index 01ac63b..99c3376 100644 --- a/test/runTest.js +++ b/test/runTest.js @@ -12,7 +12,7 @@ async function main() { extensionDevelopmentPath, extensionTestsPath, launchArgs: ['--disable-extensions'], - // vscodeExecutablePath: '/Users/mizdra/src/github.com/microsoft/vscode/scripts/code.sh', + vscodeExecutablePath: '/Users/mizdra/src/github.com/microsoft/vscode/scripts/code.sh', }); } catch (err) { console.error(err); $ npm start Error: ENAMETOOLONG: name too long, open 'data:text/javascript;base64,Y29uc3QgX3ZzY29kZUluc3RhbmNlID0gZ2xvYmFsVGhpcy5fVlNDT0RFX0lNUE9SVF9WU0NPREVfQVBJKCc5MGMzNTUwMC0yNjY0LTQ2M2...(long text)...107' at Object.readFileSync (node:fs:441:20) at t.readFileSync (node:electron/js2c/node_init:2:11013) at defaultLoadImpl (node:internal/modules/cjs/loader:1112:17) at loadSource (node:internal/modules/cjs/loader:1742:20) at Module._extensions..js (node:internal/modules/cjs/loader:1841:44) at Module.load (node:internal/modules/cjs/loader:1448:32) at Module._load (node:internal/modules/cjs/loader:1270:12) at c._load (node:electron/js2c/node_init:2:17993) at Module._load (file:///Users/mizdra/src/github.com/microsoft/vscode/out/vs/workbench/api/node/extensionHostProcess.js:68:29) at Module.load (file:///Users/mizdra/src/github.com/microsoft/vscode/out/vs/workbench/api/node/extHostExtensionService.js:32:37) at Module.load [as _load] (file:///Users/mizdra/src/github.com/microsoft/vscode/out/vs/workbench/api/node/proxyResolver.js:290:33) at TracingChannel.traceSync (node:diagnostics_channel:328:14) at wrapModuleLoad (node:internal/modules/cjs/loader:244:24) at Module.require (node:internal/modules/cjs/loader:1470:12) at require (node:internal/modules/helpers:147:16) at file:///Users/mizdra/src/github.com/mizdra/repro-vscode-test-hang/test/index.test.js:8:16 at ModuleJobSync.runSync (node:internal/modules/esm/module_job:454:37) at ModuleLoader.importSyncForRequire (node:internal/modules/esm/loader:435:47) at loadESMFromCJS (node:internal/modules/cjs/loader:1544:24) at Module._compile (node:internal/modules/cjs/loader:1695:5) at Module._extensions..js (node:internal/modules/cjs/loader:1848:10) at Module.load (node:internal/modules/cjs/loader:1448:32) at Module._load (node:internal/modules/cjs/loader:1270:12) at c._load (node:electron/js2c/node_init:2:17993) at Module._load (file:///Users/mizdra/src/github.com/microsoft/vscode/out/vs/workbench/api/node/extensionHostProcess.js:68:29) at Module.load (file:///Users/mizdra/src/github.com/microsoft/vscode/out/vs/workbench/api/node/extHostExtensionService.js:32:37) at Module.load [as _load] (file:///Users/mizdra/src/github.com/microsoft/vscode/out/vs/workbench/api/node/proxyResolver.js:290:33) at TracingChannel.traceSync (node:diagnostics_channel:328:14) at wrapModuleLoad (node:internal/modules/cjs/loader:244:24) at Module.require (node:internal/modules/cjs/loader:1470:12) at require (node:internal/modules/helpers:147:16) at Object.run (/Users/mizdra/src/github.com/mizdra/repro-vscode-test-hang/test/runner.cjs:3:3) at file:///Users/mizdra/src/github.com/microsoft/vscode/out/vs/workbench/api/common/extHostExtensionService.js:601:42 at new Promise (<anonymous>) at ExtHostExtensionService._doHandleExtensionTests (file:///Users/mizdra/src/github.com/microsoft/vscode/out/vs/workbench/api/common/extHostExtensionService.js:580:16) at async ExtHostExtensionService.$extensionTestsExecute (file:///Users/mizdra/src/github.com/microsoft/vscode/out/vs/workbench/api/common/extHostExtensionService.js:558:20)

For some reason, originalLoad.apply() appears to return a base64-encoded path generated by NodeModuleInterceptor instead of the module instance. This seems to be a Node.js bug.

Since I couldn't find a workaround, I decided to abandon intercepting require('vscode') with NodeModuleInterceptor.

mizdra · 2025-12-30T13:28:06Z

src/vs/workbench/api/node/extHostExtensionService.ts

+		// `module.registerHooks` is a generic interceptor that intercepts `require(...)`, `import ...`, and `import(...)`.
+		// However, at this time, `NodeModuleInterceptor` only intercepts `import 'vscode'` and `import('vscode')`.
+		// This can also intercept `require('vscode')`, but interception by `NodeModuleRequireInterceptor` takes precedence.
+		// In the future, we can consider migrating all interception logic to `NodeModuleInterceptor` and removing `NodeModuleRequireInterceptor`.


module._load was able to return an object from a hook. However, hooks registered via module.registerHooks currently cannot do this. Therefore, NodeModuleInterceptor circumvents this limitation by using base64-encoded source text and NodeModuleInterceptor._vscodeImportFnName. This is a complex workaround.

Incidentally, it appears Node.js plans to implement hooks that can return objects. Once implemented, this complex workaround could be removed. Porting the logic from NodeModuleRequireInterceptor to NodeModuleInterceptor should also become easier.

module: implement synchronous module evaluate hooks nodejs/node#57139

mizdra · 2025-12-30T13:30:37Z

The review is ready. Could you please review it? @mjbvz

Fix interoperability issues between require(esm) and module interce…

012b573

…ptors

mizdra commented Dec 30, 2025

View reviewed changes

vs-code-engineering bot assigned mjbvz Dec 30, 2025

mizdra commented Dec 30, 2025

View reviewed changes

mizdra marked this pull request as ready for review December 30, 2025 13:29

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

Uh oh!

Fix deadlock caused by `import 'vscode'` from modules loaded via `require(esm)` #285417

Fix deadlock caused by `import 'vscode'` from modules loaded via `require(esm)` #285417

mizdra commented Dec 30, 2025 •

edited

Loading

mizdra Dec 30, 2025

mizdra Dec 30, 2025

mizdra commented Dec 30, 2025

Labels

2 participants

Fix deadlock caused by import 'vscode' from modules loaded via require(esm) #285417

Are you sure you want to change the base?

Fix deadlock caused by import 'vscode' from modules loaded via require(esm) #285417

Conversation

mizdra commented Dec 30, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Background

How to test

mizdra Dec 30, 2025

Choose a reason for hiding this comment

mizdra Dec 30, 2025

Choose a reason for hiding this comment

mizdra commented Dec 30, 2025

Labels

2 participants

Fix deadlock caused by `import 'vscode'` from modules loaded via `require(esm)` #285417

Fix deadlock caused by `import 'vscode'` from modules loaded via `require(esm)` #285417

mizdra commented Dec 30, 2025 •

edited

Loading