Fix stack traces in throw assertions

Fixes #1372.

lib/assert.js

@@ -36,6 +36,7 @@ class AssertionError extends Error {
 		this.assertion = opts.assertion;
 		this.fixedSource = opts.fixedSource;
 		this.improperUsage = opts.improperUsage || false;
+		this.actualStack = opts.actualStack;
 		this.operator = opts.operator;
 		this.values = opts.values || [];
 
@@ -147,11 +148,14 @@ function assertExpectations({assertion, actual, expectations, message, prefix, s
 		});
 	}
 
+	const actualStack = actual.stack;
+
 	if (hasOwnProperty(expectations, 'is') && actual !== expectations.is) {
 		throw new AssertionError({
 			assertion,
 			message,
 			stack,
+			actualStack,
 			values: [
 				formatWithLabel(`${prefix} unexpected exception:`, actual),
 				formatWithLabel('Expected to be strictly equal to:', expectations.is)
@@ -164,6 +168,7 @@ function assertExpectations({assertion, actual, expectations, message, prefix, s
 			assertion,
 			message,
 			stack,
+			actualStack,
 			values: [
 				formatWithLabel(`${prefix} unexpected exception:`, actual),
 				formatWithLabel('Expected instance of:', expectations.instanceOf)
@@ -176,6 +181,7 @@ function assertExpectations({assertion, actual, expectations, message, prefix, s
 			assertion,
 			message,
 			stack,
+			actualStack,
 			values: [
 				formatWithLabel(`${prefix} unexpected exception:`, actual),
 				formatWithLabel('Expected name to equal:', expectations.name)
@@ -188,6 +194,7 @@ function assertExpectations({assertion, actual, expectations, message, prefix, s
 			assertion,
 			message,
 			stack,
+			actualStack,
 			values: [
 				formatWithLabel(`${prefix} unexpected exception:`, actual),
 				formatWithLabel('Expected message to equal:', expectations.message)
@@ -200,6 +207,7 @@ function assertExpectations({assertion, actual, expectations, message, prefix, s
 			assertion,
 			message,
 			stack,
+			actualStack,
 			values: [
 				formatWithLabel(`${prefix} unexpected exception:`, actual),
 				formatWithLabel('Expected message to match:', expectations.message)
@@ -212,6 +220,7 @@ function assertExpectations({assertion, actual, expectations, message, prefix, s
 			assertion,
 			message,
 			stack,
+			actualStack,
 			values: [
 				formatWithLabel(`${prefix} unexpected exception:`, actual),
 				formatWithLabel('Expected code to equal:', expectations.code)
@@ -433,6 +442,7 @@ function wrapAssertions(callbacks) {
 				fail(this, new AssertionError({
 					assertion: 'throwsAsync',
 					message,
+					actualStack: actual.stack,
 					values: [formatWithLabel('Function threw synchronously. Use `t.throws()` instead:', actual)]
 				}));
 				return Promise.resolve();
@@ -467,6 +477,7 @@ function wrapAssertions(callbacks) {
 				fail(this, new AssertionError({
 					assertion: 'notThrows',
 					message,
+					actualStack: error.stack,
 					values: [formatWithLabel('Function threw:', error)]
 				}));
 				return;
@@ -493,7 +504,7 @@ function wrapAssertions(callbacks) {
 					throw new AssertionError({
 						assertion: 'notThrowsAsync',
 						message,
-						stack,
+						actualStack: stack,
 						values: [formatWithLabel(`${wasReturned ? 'Returned promise' : 'Promise'} rejected with:`, reason)]
 					});
 				});
@@ -513,6 +524,7 @@ function wrapAssertions(callbacks) {
 				fail(this, new AssertionError({
 					assertion: 'notThrowsAsync',
 					message,
+					actualStack: error.stack,
 					values: [formatWithLabel('Function threw:', error)]
 				}));
 				return Promise.resolve();

lib/serialize-error.js

@@ -60,6 +60,10 @@ function trySerializeError(err, shouldBeautifyStack) {
 		stack
 	};
 
+	if (err.actualStack) {
+		retval.stack = shouldBeautifyStack ? beautifyStack(err.actualStack) : err.actualStack;
+	}
+
 	if (retval.avaAssertionError) {
 		retval.improperUsage = err.improperUsage;
 		retval.message = err.message;

test/fixture/report/regular/traces-in-t-throws.js

@@ -0,0 +1,29 @@
+import test from '../../../..';
+
+function throwError() {
+	throw new Error('uh-oh');
+}
+
+function returnRejectedPromise() {
+	return Promise.reject(new Error('uh-oh'));
+}
+
+test('throws', t => {
+	t.throws(() => throwError(), TypeError);
+});
+
+test('notThrows', t => {
+	t.notThrows(() => throwError());
+});
+
+test('notThrowsAsync', t => {
+	t.notThrowsAsync(() => throwError());
+});
+
+test('throwsAsync', t => {
+	t.throwsAsync(() => throwError(), TypeError);
+});
+
+test('throwsAsync different error', t => {
+	return t.throwsAsync(returnRejectedPromise, TypeError);
+});