Ensure package.json is writable in *.vsix

VSC requires the manifest file unpacked from the .vsix archive to be
marked as writable (see [1]). Since generating writable artifacts is
difficult in some build systems (such as Bazel), it would be helpful if
vsce itself could ensure that the file mode of the manifest is correct.

With this commit, the correct file mode on `package.json` is set
automatically by the packaging process via a new `Processor` and yazl's
`mode` argument.

[1]: https://github.com/microsoft/vscode/blob/88144f6d31718288c7a2c6fb741e0646d40804cf/src/vs/platform/extensionManagement/node/extensionsScanner.ts#L144

Author: fmeum

src/package.ts

@@ -37,11 +37,13 @@ const MinimatchOptions: minimatch.IOptions = { dot: true };
 
 export interface IInMemoryFile {
 	path: string;
+	mode?: number;
 	readonly contents: Buffer | string;
 }
 
 export interface ILocalFile {
 	path: string;
+	mode?: number;
 	readonly localPath: string;
 }
 
@@ -274,6 +276,18 @@ class ManifestProcessor extends BaseProcessor {
 		}
 	}
 
+	async onFile(file: IFile): Promise<IFile> {
+		const path = util.normalize(file.path);
+
+		if (!/^extension\/package.json$/i.test(path)) {
+			return Promise.resolve(file);
+		}
+
+		// Ensure that package.json is writable as VS Code needs to
+		// store metadata in the extracted file.
+		return { ...file, mode: 0o100644 };
+	}
+
 	async onEnd(): Promise<void> {
 		if (typeof this.manifest.extensionKind === 'string') {
 			util.log.warn(
@@ -1104,8 +1118,10 @@ function writeVsix(files: IFile[], packagePath: string): Promise<void> {
 					const zip = new yazl.ZipFile();
 					files.forEach(f =>
 						isInMemoryFile(f)
-							? zip.addBuffer(typeof f.contents === 'string' ? Buffer.from(f.contents, 'utf8') : f.contents, f.path)
-							: zip.addFile(f.localPath, f.path)
+							? zip.addBuffer(typeof f.contents === 'string' ? Buffer.from(f.contents, 'utf8') : f.contents, f.path, {
+									mode: f.mode,
+							  })
+							: zip.addFile(f.localPath, f.path, { mode: f.mode })
 					);
 					zip.end();