src/vs/workbench/services/dialogs/browser/fileDialogService.ts/FileDialogService/showOpenDialog
class FileDialogService:	async showOpenDialog(options: IOpenDialogOptions): Promise<URI[] | undefined> {
		const schema = this.getFileSystemSchema(options);

		if (this.shouldUseSimplified(schema)) {
			return super.showOpenDialogSimplified(schema, options);
		}

		if (!WebFileSystemAccess.supported(window)) {
			return this.showUnsupportedBrowserWarning('open');
		}

		let uri: URI | undefined;
		const startIn = Iterable.first(this.fileSystemProvider.directories) ?? 'documents';

		try {
			if (options.canSelectFiles) {
				const handle = await window.showOpenFilePicker({ multiple: false, types: this.getFilePickerTypes(options.filters), ...{ startIn } });
				if (handle.length === 1 && WebFileSystemAccess.isFileSystemFileHandle(handle[0])) {
					uri = await this.fileSystemProvider.registerFileHandle(handle[0]);
				}
			} else {
				const handle = await window.showDirectoryPicker({ ...{ startIn } });
				uri = await this.fileSystemProvider.registerDirectoryHandle(handle);
			}
		} catch (error) {
			// ignore - `showOpenFilePicker` / `showDirectoryPicker` will throw an error when the user cancels
		}

		return uri ? [uri] : undefined;
	}