assert: accept regular expressions to validate

doc/api/assert.md

@@ -1069,27 +1069,62 @@ changes:
 Expects the function `block` to throw an error.
 
 If specified, `error` can be a [`Class`][], [`RegExp`][], a validation function,
-an object where each property will be tested for, or an instance of error where
-each property will be tested for including the non-enumerable `message` and
-`name` properties.
+an validation object where each property will be tested for strict deep
+equality, or an instance of error where each property will be tested for strict
+deep equality including the non-enumerable `message` and `name` properties. When
+using an validation object, it is also possible to use a regular expression,
+when validating against a string property. See below for examples.
 
 If specified, `message` will be the message provided by the `AssertionError` if
 the block fails to throw.
 
-Custom error object / error instance:
+Custom validation object / error instance:
 
 ```js
 const err = new TypeError('Wrong value');
 err.code = 404;
+err.foo = 'bar';
+err.info = {
+  nested: true,
+  baz: 'text'
+};
+err.reg = /abc/i;
 
 assert.throws(
   () => {
     throw err;
   },
   {
     name: 'TypeError',
-    message: 'Wrong value'
-    // Note that only properties on the error object will be tested!
+    message: 'Wrong value',
+    info: {
+      nested: true,
+      baz: 'text'
+    }
+    // Note that only properties on the validation object will be tested for.
+    // Using nested objects requires all properties to be present. Otherwise
+    // the validation is going to fail.
+  }
+);
+
+// Using regular expressions to validate the error properties:
+assert.throws(
+  () => {
+    throw err;
+  },
+  {
+    name: /^TypeError$/,
+    message: /Wrong/,
+    foo: 'bar',
+    info: {
+      nested: true,
+      // Note that it is not possible to use regular expressions for nested
+      // properties!
+      baz: 'text'
+    },
+    // This will strictly validate that the regular expression is identical to
+    // the regular expression on the error.
+    reg: /abc/i
   }
 );
 

lib/assert.js

@@ -35,7 +35,7 @@ const {
   }
 } = require('internal/errors');
 const { openSync, closeSync, readSync } = require('fs');
-const { inspect, types: { isPromise } } = require('util');
+const { inspect, types: { isPromise, isRegExp } } = require('util');
 const { EOL } = require('os');
 const { NativeModule } = require('internal/bootstrap/loaders');
 
@@ -362,10 +362,18 @@ assert.notStrictEqual = function notStrictEqual(actual, expected, message) {
 };
 
 class Comparison {
-  constructor(obj, keys) {
+  constructor(obj, keys, actual) {
     for (const key of keys) {
-      if (key in obj)
-        this[key] = obj[key];
+      if (key in obj) {
+        if (actual !== undefined &&
+            typeof actual[key] === 'string' &&
+            isRegExp(obj[key]) &&
+            obj[key].test(actual[key])) {
+          this[key] = actual[key];
+        } else {
+          this[key] = obj[key];
+        }
+      }
     }
   }
 }
@@ -375,7 +383,7 @@ function compareExceptionKey(actual, expected, key, message, keys) {
     if (!message) {
       // Create placeholder objects to create a nice output.
       const a = new Comparison(actual, keys);
-      const b = new Comparison(expected, keys);
+      const b = new Comparison(expected, keys, actual);
 
       const tmpLimit = Error.stackTraceLimit;
       Error.stackTraceLimit = 0;
@@ -415,6 +423,11 @@ function expectedException(actual, expected, msg) {
       keys.push('name', 'message');
     }
     for (const key of keys) {
+      if (typeof actual[key] === 'string' &&
+          isRegExp(expected[key]) &&
+          expected[key].test(actual[key])) {
+        continue;
+      }
       compareExceptionKey(actual, expected, key, msg, keys);
     }
     return true;

test/parallel/test-assert.js

@@ -914,3 +914,29 @@ assert.throws(
     }
   );
 }
+
+assert.throws(
+  () => { throw new TypeError('foobar'); },
+  {
+    message: /foo/,
+    name: /^TypeError$/
+  }
+);
+
+assert.throws(
+  () => assert.throws(
+    () => { throw new TypeError('foobar'); },
+    {
+      message: /fooa/,
+      name: /^TypeError$/
+    }
+  ),
+  {
+    message: `${start}\n${actExp}\n\n` +
+             '  Comparison {\n' +
+             "-   message: 'foobar',\n" +
+             '+   message: /fooa/,\n' +
+             "    name: 'TypeError'\n" +
+             '  }'
+  }
+);