Check that modules in both the base package.json and remote/ have the same version installed

build/npm/postinstall.js

@@ -79,3 +79,41 @@ if (fs.existsSync(processTreeDts)) {
 	console.log('Removing windows-process-tree.d.ts');
 	fs.unlinkSync(processTreeDts);
 }
+
+function getInstalledVersion(packageName, cwd) {
+	const opts = {};
+	if (cwd) {
+		opts.cwd = cwd;
+	}
+
+	const result = cp.spawnSync(yarn, ['list', '--pattern', packageName], opts);
+	const stdout = result.stdout.toString();
+	const match = stdout.match(new RegExp(packageName + '@(\\S+)'));
+	if (!match || !match[1]) {
+		throw new Error('Unexpected output from yarn list: ' + stdout);
+	}
+
+	return match[1];
+}
+
+function assertSameVersionsBetweenFolders(packageName, otherFolder) {
+	const baseVersion = getInstalledVersion(packageName);
+	const otherVersion = getInstalledVersion(packageName, otherFolder);
+
+	if (baseVersion !== otherVersion) {
+		throw new Error(`Mismatched versions installed for ${packageName}: root has ${baseVersion}, ./${otherFolder} has ${otherVersion}. These should be the same!`);
+	}
+}
+
+// Check that modules in both the base package.json and remote/ have the same version installed
+const requireSameVersionsInRemote = [
+	'xterm',
+	'xterm-addon-search',
+	'xterm-addon-web-links',
+	'node-pty',
+	'vscode-ripgrep'
+];
+
+requireSameVersionsInRemote.forEach(packageName => {
+	assertSameVersionsBetweenFolders(packageName, 'remote');
+});