Electron File Dialog Can't Open Read-only Files

[colin-grant-work]

Bug Description:

Before returning from .showOpenDialog(), the ElectronFileDialogService checks whether the selected files are both readable and writable for the current user. It seems the check for writability makes sense for the .showSaveDialog() method, but not necessarily for the .showOpenDialog() case, since 'opening' doesn't necessarily imply writing.

theia/packages/filesystem/src/electron-browser/file-dialog/electron-file-dialog-service.ts

Lines 47 to 61 in 7e09e93

	async showOpenDialog(props: OpenFileDialogProps, folder?: FileStat): Promise<MaybeArray<URI> | undefined> {
	const rootNode = await this.getRootNode(folder);
	if (rootNode) {
	const { filePaths } = await remote.dialog.showOpenDialog(this.toOpenDialogOptions(rootNode.uri, props));
	if (filePaths.length === 0) {
	return undefined;
	}
	const uris = filePaths.map(path => FileUri.create(path));
	const canAccess = await this.canReadWrite(uris);
	const result = canAccess ? uris.length === 1 ? uris[0] : uris : undefined;
	return result;
	}
	return undefined;
	}

theia/packages/filesystem/src/electron-browser/file-dialog/electron-file-dialog-service.ts

Lines 83 to 91 in 7e09e93

	protected async canReadWrite(uris: MaybeArray<URI>): Promise<boolean> {
	for (const uri of Array.isArray(uris) ? uris : [uris]) {
	if (!(await this.fileService.access(uri, FileAccess.Constants.R_OK | FileAccess.Constants.W_OK))) {
	this.messageService.error(`Cannot access resource at ${uri.path}.`);
	return false;
	}
	}
	return true;
	}

Steps to Reproduce:

1. On a multi-user system, find or create a file that certain users can read but not write
2. As a user who can read but not write to a given file, try to 'open' the file using the file dialog
3. See an error toast Cannot access resource at <path>.

• Operating System: RHEL7
• Theia Version: 7e09e93

[tsmaeder]

Sounds like a low hanging fruit for a new contributor.

[kejsitake]

Hi! I submitted a PR. I would be happy to make any other changes if necessary.