JavaScript: Windows compatibility when spawning npm etc.

On Windows we need to spawn `npm.cmd` if we don't want to use `{ shell: true }`.

Author: knutwannheden

rewrite-javascript/rewrite/src/javascript/format/prettier-config-loader.ts

@@ -20,6 +20,7 @@ import * as os from 'os';
 import {spawnSync} from 'child_process';
 import {prettierStyle, PrettierStyle} from '../style';
 import {randomId} from '../../uuid';
+import {getPlatformCommand} from '../../shell-utils';
 
 /**
  * Cache of loaded Prettier modules by version.
@@ -97,7 +98,7 @@ async function installPrettierToCache(version: string): Promise<void> {
     );
 
     // Run npm install
-    const result = spawnSync('npm', ['install', '--silent'], {
+    const result = spawnSync(getPlatformCommand('npm'), ['install', '--silent'], {
         cwd: cacheDir,
         encoding: 'utf-8',
         stdio: ['pipe', 'pipe', 'pipe'],

rewrite-javascript/rewrite/src/javascript/package-manager.ts

@@ -28,6 +28,7 @@ import {PlainTextParser} from "../text";
 import {SourceFile} from "../tree";
 import {TreeVisitor} from "../visitor";
 import {ExecutionContext} from "../execution";
+import {getPlatformCommand} from "../shell-utils";
 import * as fs from "fs";
 import * as fsp from "fs/promises";
 import * as path from "path";
@@ -231,7 +232,7 @@ function runInstall(pm: PackageManager, options: InstallOptions): PackageManager
     const [cmd, ...args] = command;
 
     try {
-        const result = spawnSync(cmd, args, {
+        const result = spawnSync(getPlatformCommand(cmd), args, {
             cwd: options.cwd,
             encoding: 'utf-8',
             stdio: ['pipe', 'pipe', 'pipe'],
@@ -285,7 +286,7 @@ export function runList(pm: PackageManager, cwd: string, timeout: number = 30000
 
     const [cmd, ...args] = config.listCommand;
 
-    const result = spawnSync(cmd, args, {
+    const result = spawnSync(getPlatformCommand(cmd), args, {
         cwd,
         encoding: 'utf-8',
         stdio: ['pipe', 'pipe', 'pipe'],

rewrite-javascript/rewrite/src/rpc/request/install-recipes.ts

@@ -19,6 +19,7 @@ import * as fs from "fs";
 import {spawn} from "child_process";
 import {withMetrics} from "./metrics";
 import {RecipeMarketplace} from "../../marketplace";
+import {getPlatformCommand} from "../../shell-utils";
 
 export interface InstallRecipesResponse {
     recipesInstalled: number
@@ -35,7 +36,7 @@ async function spawnNpmCommand(
     logger?: rpc.Logger,
     logPrefix?: string
 ): Promise<void> {
-    const child = spawn(command, args, {cwd});
+    const child = spawn(getPlatformCommand(command), args, {cwd});
 
     if (logger) {
         const prefix = logPrefix ? `${logPrefix}: ` : '';

rewrite-javascript/rewrite/src/shell-utils.ts

@@ -0,0 +1,45 @@
+/*
+ * Copyright 2025 the original author or authors.
+ * <p>
+ * Licensed under the Moderne Source Available License (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ * <p>
+ * https://docs.moderne.io/licensing/moderne-source-available-license
+ * <p>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+import * as os from 'os';
+
+/**
+ * Utility functions for cross-platform shell command execution.
+ */
+
+/**
+ * Commands that are implemented as .cmd scripts on Windows.
+ * These need a .cmd suffix when spawned without `shell: true`.
+ */
+const CMD_SCRIPT_COMMANDS = new Set(['npm', 'npx', 'yarn', 'pnpm', 'pnpx']);
+
+/**
+ * Returns the correct command name for the current platform.
+ * On Windows, Node.js package manager commands (npm, npx, yarn, pnpm) are
+ * implemented as .cmd scripts and require the .cmd extension when spawned
+ * without `shell: true`.
+ *
+ * Note: `bun` uses a native executable (bun.exe) on Windows, not a .cmd script,
+ * so it doesn't need special handling.
+ *
+ * @param command The base command name (e.g., 'npm', 'yarn', 'pnpm')
+ * @returns The platform-appropriate command name
+ */
+export function getPlatformCommand(command: string): string {
+    if (os.platform() === 'win32' && CMD_SCRIPT_COMMANDS.has(command)) {
+        return `${command}.cmd`;
+    }
+    return command;
+}