Some extensions break on Windows for Insiders 1.100.0

[Jason3S]

Does this issue occur when all extensions are disabled?: Yes/No

• VS Code Version: 1.100.0-insider
• OS Version: Windows_NT x64 10.0.26100

Version: 1.100.0-insider (user setup)
Commit: c73f02083edc88e5c72a8c6cc301fb8a6430493f
Date: 2025-04-15T05:04:09.439Z
Electron: 34.4.1
ElectronBuildId: 11317338
Chromium: 132.0.6834.210
Node.js: 20.18.3
V8: 13.2.152.41-electron.0
OS: Windows_NT x64 10.0.26100

Looks like Insiders does something weird if the extension package.json type is module.

Error:

Activating extension 'vscode-samples.lsp-sample' failed: Only URLs with a scheme in: file, data, node, and electron are supported by the default ESM loader. On Windows, absolute paths must be valid file:// URLs. Received protocol 'c:'.

Steps to Reproduce:

1. Clone
2. Apply diff

diff --git a/lsp-sample/.vscode/launch.json b/lsp-sample/.vscode/launch.json
index 4ba56122..9967a439 100644
--- a/lsp-sample/.vscode/launch.json
+++ b/lsp-sample/.vscode/launch.json
@@ -7,7 +7,7 @@
 			"request": "launch",
 			"name": "Launch Client",
 			"runtimeExecutable": "${execPath}",
-			"args": ["--extensionDevelopmentPath=${workspaceRoot}"],
+			"args": ["--disable-extensions", "--extensionDevelopmentPath=${workspaceRoot}"],
 			"outFiles": [
 				"${workspaceRoot}/client/out/**/*.js",
 				"${workspaceRoot}/server/out/**/*.js"
diff --git a/lsp-sample/client/package.json b/lsp-sample/client/package.json
index edf92a8b..99478ec1 100644
--- a/lsp-sample/client/package.json
+++ b/lsp-sample/client/package.json
@@ -3,6 +3,7 @@
 	"description": "VSCode part of a language server",
 	"author": "Microsoft Corporation",
 	"license": "MIT",
+	"type": "module",
 	"version": "0.0.1",
 	"publisher": "vscode",
 	"repository": {
diff --git a/lsp-sample/package.json b/lsp-sample/package.json
index d9738f72..17736e05 100644
--- a/lsp-sample/package.json
+++ b/lsp-sample/package.json
@@ -19,7 +19,8 @@
 	"activationEvents": [
 		"onLanguage:plaintext"
 	],
-	"main": "./client/out/extension",
+	"type": "module",
+	"main": "./client/out/extension.cjs",
 	"contributes": {
 		"configuration": {
 			"type": "object",

3. Rename ./lsp-sample/src/extension.ts to ./lsp-sample/src/extension.cts
4. cd into lsp-sample
5. open insiders
6. Launch the lsp-sample extension

[Jason3S]

Related to: streetsidesoftware/vscode-spell-checker#4303

[Jason3S]

@jrieken, I think it is related to this PR: #245214

For some reason it is using a file path instead of a URL string, see line 256.

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

Lines 255 to 259 in 101d052

	if (mode === 'esm') {
	r = <T>await import(module.fsPath);
	} else {
	r = <T>require(module.fsPath);
	}

[jrieken]

Good catch - on macOS the absolute (posix) path seems to work but I haven't tried this on windows 🙊. Pushed a change to use the full file-uri and testing on windows right now

[Jason3S]

@jrieken,
Thank you for the quick fix.