[Fix] assertion: pass through assertion return value, for promises

Author: ljharb

lib/test.js

@@ -972,7 +972,7 @@ Test.prototype.doesNotMatch = function doesNotMatch(string, regexp, msg, extra)
 };
 
 Test.prototype.assertion = function assertion(fn) {
-	callBind.apply(fn)(this, $slice(arguments, 1));
+	return callBind.apply(fn)(this, $slice(arguments, 1));
 };
 
 // eslint-disable-next-line no-unused-vars

package.json

@@ -61,6 +61,7 @@
 		"npmignore": "^0.3.1",
 		"nyc": "^10.3.2",
 		"safe-publish-latest": "^2.0.0",
+		"semver": "^6.3.1",
 		"tap": "^8.0.1",
 		"tap-parser": "^5.4.0"
 	},

test/assertion.js

@@ -3,6 +3,7 @@
 var tape = require('../');
 var tap = require('tap');
 var concat = require('concat-stream');
+var satisfies = require('semver').satisfies;
 
 var stripFullStack = require('./common').stripFullStack;
 
@@ -32,17 +33,34 @@ tap.test('using a custom assertion', function (tt) {
 			'          at Test.<anonymous> ($TEST/assertion.js:$LINE:$COL)',
 			'          [... stack stripped ...]',
 			'  ...',
+			typeof Promise === 'undefined'
+				? '# SKIP custom assertion returns a promise'
+				: [].concat(
+					'# custom assertion returns a promise',
+					'ok ' + ++count + ' promise rejected!',
+					'not ok ' + ++count + ' SyntaxError: expected promise to reject; it fulfilled',
+					'  ---',
+					'    operator: error',
+					'    stack: |-',
+					'      SyntaxError: expected promise to reject; it fulfilled',
+					'          at $TEST/assertion.js:$LINE:$COL',
+					satisfies(process.version, '^8 || ^9')
+						? '          at <anonymous>'
+						: [],
+					'          [... stack stripped ...]',
+					'  ...'
+				),
 			'',
 			'1..' + count,
 			'# tests ' + count,
-			'# pass  ' + (count - 1),
-			'# fail  1',
+			'# pass  ' + (count - (typeof Promise === 'undefined' ? 1 : 2)),
+			'# fail  ' + (typeof Promise === 'undefined' ? 1 : 2),
 			''
 		));
 	}));
 
 	var isAnswer = function (value, msg) {
-		// eslint-disable-next-line no-invalid-this
+
 		this.equal(value, 42, msg || 'value must be the answer to life, the universe, and everything');
 	};
 
@@ -54,4 +72,33 @@ tap.test('using a custom assertion', function (tt) {
 
 		t.end();
 	});
+
+	var rejects = function assertRejects(fn, expected, msg, extra) {
+		var t = this;
+		/* eslint no-invalid-this: 0 */
+		return new Promise(function (resolve) { resolve(fn()); }).then(
+			function () {
+				throw new SyntaxError('expected promise to reject; it fulfilled');
+			},
+			function (err) {
+				t['throws'](function () { throw err; }, expected, msg, extra);
+			}
+		);
+	};
+
+	test('custom assertion returns a promise', { skip: typeof Promise !== 'function' }, function (t) {
+		return Promise.all([
+			t.assertion(
+				rejects,
+				function () { return Promise.resolve(); },
+				SyntaxError,
+				'expected promise to reject; it fulfilled'
+			),
+			t.assertion(
+				rejects,
+				function () { return Promise.reject(new Error('foo')); },
+				'promise rejected!'
+			)
+		]);
+	});
 });

test/common.js

@@ -95,10 +95,15 @@ module.exports.stripFullStack = function (output) {
 		/at(:?) Test.tap.test.([^ ]+)/g,
 		'at$1 Test.$2'
 	).replace(
-		// Handle stack trace variation in Node v0.8
+		// Handle more stack trace variation in Node v0.8
 		/(\[\.\.\. stack stripped \.\.\.\]\r?\n *at) <anonymous> \(([^)]+)\)/g,
 		'$1 $2'
-	).split(/\r?\n/g);
+	).replace(
+		// Handle more stack trace variation in Node v0.8
+		/at(:?) Test\.t /g,
+		'at$1 Test.<anonymous> '
+	)
+		.split(/\r?\n/g);
 };
 
 module.exports.runProgram = function (folderName, fileName, cb) {