Preserve stacktrace when wrapping errors (#935)

source/errors.ts

@@ -7,7 +7,7 @@ export class GotError extends Error {
 	code?: string;
 	readonly options: NormalizedOptions;
 
-	constructor(message: string, error: (Error & {code?: string}) | {code?: string}, options: NormalizedOptions) {
+	constructor(message: string, error: Partial<Error & {code?: string}>, options: NormalizedOptions) {
 		super(message);
 		Error.captureStackTrace(this, this.constructor);
 		this.name = 'GotError';
@@ -19,6 +19,20 @@ export class GotError extends Error {
 		Object.defineProperty(this, 'options', {
 			value: options
 		});
+
+		// Recover the original stacktrace
+		if (!is.undefined(error.stack)) {
+			const indexOfMessage = this.stack.indexOf(this.message) + this.message.length;
+			const thisStackTrace = this.stack.slice(indexOfMessage).split('\n').reverse();
+			const errorStackTrace = error.stack.slice(error.stack.indexOf(error.message) + error.message.length).split('\n').reverse();
+
+			// Remove duplicated traces
+			while (errorStackTrace.length !== 0 && errorStackTrace[0] === thisStackTrace[0]) {
+				thisStackTrace.shift();
+			}
+
+			this.stack = `${this.stack.slice(0, indexOfMessage)}${thisStackTrace.reverse().join('\n')}${errorStackTrace.reverse().join('\n')}`;
+		}
 	}
 }
 
@@ -96,7 +110,7 @@ export class TimeoutError extends GotError {
 	event: string;
 
 	constructor(error: TimedOutError, timings: Timings, options: NormalizedOptions) {
-		super(error.message, {code: 'ETIMEDOUT'}, options);
+		super(error.message, error, options);
 		this.name = 'TimeoutError';
 		this.event = error.event;
 		this.timings = timings;

source/request-as-event-emitter.ts

@@ -14,6 +14,7 @@ import {CacheError, MaxRedirectsError, RequestError, TimeoutError} from './error
 import urlToOptions from './utils/url-to-options';
 import {NormalizedOptions, Response, ResponseObject} from './utils/types';
 
+const setImmediateAsync = () => new Promise(resolve => setImmediate(resolve));
 const pipeline = promisify(stream.pipeline);
 
 const redirectCodes: ReadonlySet<number> = new Set([300, 301, 302, 303, 304, 307, 308]);
@@ -283,7 +284,13 @@ export default (options: NormalizedOptions) => {
 		}
 	};
 
-	setImmediate(async () => {
+	(async () => {
+		// Promises are executed immediately.
+		// If there were no `setImmediate` here,
+		// `promise.json()` would have no effect
+		// as the request would be sent already.
+		await setImmediateAsync();
+
 		try {
 			for (const hook of options.hooks.beforeRequest) {
 				// eslint-disable-next-line no-await-in-loop
@@ -294,7 +301,7 @@ export default (options: NormalizedOptions) => {
 		} catch (error) {
 			emitError(error);
 		}
-	});
+	})();
 
 	return emitter;
 };

test/error.ts

@@ -197,3 +197,17 @@ test('errors are thrown directly when options.stream is true', t => {
 		message: 'Parameter `hooks` must be an Object, not boolean'
 	});
 });
+
+test('the old stacktrace is recovered', async t => {
+	const error = await t.throwsAsync(got('https://example.com', {
+		request: () => {
+			throw new Error('foobar');
+		}
+	}));
+
+	t.true(error.stack.includes('at Object.request'));
+
+	// The first `at get` points to where the error was wrapped,
+	// the second `at get` points to the real cause.
+	t.not(error.stack.indexOf('at get'), error.stack.lastIndexOf('at get'));
+});