Use 'r+' with truncation when saving existing files on Windows (#42899)

* Use 'r+' with truncation when saving existing files on Windows

Opening a file with 'w' flag removes its alternate data streams. To
prevent this, extend the logic used for hidden files to all existing
files.

Fixes: https://github.com/Microsoft/vscode/issues/6363

* adopt truncate for saving as admin

src/vs/code/node/cli.ts

@@ -87,18 +87,17 @@ export async function main(argv: string[]): Promise<any> {
 
 			// Write source to target
 			const data = fs.readFileSync(source);
-			try {
+			if (isWindows) {
+				// On Windows we use a different strategy of saving the file
+				// by first truncating the file and then writing with r+ mode.
+				// This helps to save hidden files on Windows
+				// (see https://github.com/Microsoft/vscode/issues/931) and
+				// prevent removing alternate data streams
+				// (see https://github.com/Microsoft/vscode/issues/6363)
+				fs.truncateSync(target, 0);
+				writeFileAndFlushSync(target, data, { flag: 'r+' });
+			} else {
 				writeFileAndFlushSync(target, data);
-			} catch (error) {
-				// On Windows and if the file exists with an EPERM error, we try a different strategy of saving the file
-				// by first truncating the file and then writing with r+ mode. This helps to save hidden files on Windows
-				// (see https://github.com/Microsoft/vscode/issues/931)
-				if (isWindows && error.code === 'EPERM') {
-					fs.truncateSync(target, 0);
-					writeFileAndFlushSync(target, data, { flag: 'r+' });
-				} else {
-					throw error;
-				}
 			}
 
 			// Restore previous mode as needed

src/vs/workbench/services/files/electron-browser/fileService.ts

@@ -607,22 +607,23 @@ export class FileService extends Disposable implements IFileService {
 				return addBomPromise.then(addBom => {
 
 					// 4.) set contents and resolve
-					return this.doSetContentsAndResolve(resource, absolutePath, value, addBom, encodingToWrite).then(void 0, error => {
-						if (!exists || error.code !== 'EPERM' || !isWindows) {
-							return TPromise.wrapError(error);
-						}
+					if (!exists || !isWindows) {
+						return this.doSetContentsAndResolve(resource, absolutePath, value, addBom, encodingToWrite);
+					}
 
-						// On Windows and if the file exists with an EPERM error, we try a different strategy of saving the file
-						// by first truncating the file and then writing with r+ mode. This helps to save hidden files on Windows
-						// (see https://github.com/Microsoft/vscode/issues/931)
+					// On Windows and if the file exists, we use a different strategy of saving the file
+					// by first truncating the file and then writing with r+ mode. This helps to save hidden files on Windows
+					// (see https://github.com/Microsoft/vscode/issues/931) and prevent removing alternate data streams
+					// (see https://github.com/Microsoft/vscode/issues/6363)
+					else {
 
-						// 5.) truncate
+						// 4.) truncate
 						return pfs.truncate(absolutePath, 0).then(() => {
 
-							// 6.) set contents (this time with r+ mode) and resolve again
+							// 5.) set contents (with r+ mode) and resolve
 							return this.doSetContentsAndResolve(resource, absolutePath, value, addBom, encodingToWrite, { flag: 'r+' });
 						});
-					});
+					}
 				});
 			});
 		}).then(null, error => {