async function pickFile()

in quickinput-sample/src/quickOpen.ts [49:112]
64 lines of code
13 McCabe index (conditional complexity)

async function pickFile() {
	const disposables: Disposable[] = [];
	try {
		return await new Promise<Uri | undefined>((resolve, reject) => {
			const input = window.createQuickPick<FileItem | MessageItem>();
			input.placeholder = 'Type to search for files';
			let rgs: cp.ChildProcess[] = [];
			disposables.push(
				input.onDidChangeValue(value => {
					rgs.forEach(rg => rg.kill());
					if (!value) {
						input.items = [];
						return;
					}
					input.busy = true;
					const cwds = workspace.workspaceFolders ? workspace.workspaceFolders.map(f => f.uri.fsPath) : [process.cwd()];
					const q = process.platform === 'win32' ? '"' : '\'';
					rgs = cwds.map(cwd => {
						const rg = cp.exec(`rg --files -g ${q}*${value}*${q}`, { cwd }, (err, stdout) => {
							const i = rgs.indexOf(rg);
							if (i !== -1) {
								if (rgs.length === cwds.length) {
									input.items = [];
								}
								if (!err) {
									input.items = input.items.concat(
										stdout
											.split('\n').slice(0, 50)
											.map(relative => new FileItem(Uri.file(cwd), Uri.file(path.join(cwd, relative))))
									);
								}
								if (err && !(<any>err).killed && (<any>err).code !== 1 && err.message) {
									input.items = input.items.concat([
										new MessageItem(Uri.file(cwd), err.message)
									]);
								}
								rgs.splice(i, 1);
								if (!rgs.length) {
									input.busy = false;
								}
							}
						});
						return rg;
					});
				}),
				input.onDidChangeSelection(items => {
					const item = items[0];
					if (item instanceof FileItem) {
						resolve(item.uri);
						input.hide();
					}
				}),
				input.onDidHide(() => {
					rgs.forEach(rg => rg.kill());
					resolve(undefined);
					input.dispose();
				})
			);
			input.show();
		});
	} finally {
		disposables.forEach(d => d.dispose());
	}
}