assert: add more information to AssertionErrors

This adds information about the actual thrown error to the
AssertionError's message property.

It also improves the logged error instances error name by using the
constructors name, if available.

PR-URL: https://github.com/nodejs/node/pull/28263
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

3 files changed, 16 insertions, 5 deletions

diff --git a/lib/assert.js b/lib/assert.js
index 50ab6b39b1..0b256e604e 100644
--- a/lib/assert.js
+++ b/lib/assert.js
@@ -620,8 +620,13 @@ function expectedException(actual, expected, message, fn) {
       generatedMessage = true;
       message = 'The error is expected to be an instance of ' +
         `"${expected.name}". Received `;
+      // TODO: Special handle identical names.
       if (isError(actual)) {
-        message += `"${actual.name}"`;
+        const name = actual.constructor && actual.constructor.name;
+        message += `"${name || actual.name}"`;
+        if (actual.message) {
+          message += `\n\nError message:\n\n${actual.message}`;
+        }
       } else {
         message += `"${inspect(actual, { depth: -1 })}"`;
       }
@@ -636,6 +641,10 @@ function expectedException(actual, expected, message, fn) {
         const name = expected.name ? `"${expected.name}" ` : '';
         message = `The ${name}validation function is expected to return` +
           ` "true". Received ${inspect(res)}`;
+
+        if (isError(actual)) {
+          message += `\n\nCaught error:\n\n${actual}`;
+        }
       }
       throwError = true;
     }
diff --git a/test/parallel/test-assert-async.js b/test/parallel/test-assert-async.js
index 45447d4563..cbb4431f19 100644
--- a/test/parallel/test-assert-async.js
+++ b/test/parallel/test-assert-async.js
@@ -73,7 +73,8 @@ const invalidThenableFunc = () => {
     () => assert.rejects(Promise.reject(err), validate),
     {
       message: 'The "validate" validation function is expected to ' +
-               "return \"true\". Received 'baz'",
+               "return \"true\". Received 'baz'\n\nCaught error:\n\n" +
+               'Error: foobar',
       code: 'ERR_ASSERTION',
       actual: err,
       expected: validate,
diff --git a/test/parallel/test-assert.js b/test/parallel/test-assert.js
index 9c59227a78..07cf374696 100644
--- a/test/parallel/test-assert.js
+++ b/test/parallel/test-assert.js
@@ -133,7 +133,7 @@ assert.throws(
     name: 'AssertionError',
     operator: 'throws',
     message: 'The error is expected to be an instance of "AssertionError". ' +
-             'Received "TypeError"'
+             'Received "TypeError"\n\nError message:\n\n[object Object]'
   }
 );
 
@@ -255,7 +255,7 @@ a.throws(() => thrower(TypeError), (err) => {
       assert.strictEqual(
         err.message,
         'The error is expected to be an instance of "ES6Error". ' +
-          'Received "Error"'
+          'Received "AnotherErrorType"\n\nError message:\n\nfoo'
       );
       assert.strictEqual(err.actual, actual);
       return true;
@@ -1334,7 +1334,8 @@ assert.throws(
     () => assert.throws(() => { throw err; }, validate),
     {
       message: 'The validation function is expected to ' +
-              `return "true". Received ${inspect(validate())}`,
+              `return "true". Received ${inspect(validate())}\n\nCaught ` +
+              `error:\n\n${err}`,
       code: 'ERR_ASSERTION',
       actual: err,
       expected: validate,