From 11d44c63d0391b157b520cc7a2d19ca08beb894b Mon Sep 17 00:00:00 2001
From: Lance Ball <lball@redhat.com>
Date: Wed, 22 Nov 2017 13:49:50 -0500
Subject: [PATCH] test: make common.mustNotCall show file:linenumber
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

When a test fails via `common.mustNotCall` it is sometimes hard to
determine exactly what was called. This modification stores the
caller's file and line number by using the V8 Error API to capture
a stack at the time `common.mustNotCall()` is called. In the event
of failure, this information is printed.

This change also exposes a new function in test/common, `getCallSite()`
which accepts a `function` and returns a `String` with the file name and
line number for the function.

PR-URL: https://github.com/nodejs/node/pull/17257
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Gibson Fahnestock <gibfahn@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: Sakthipriyan Vairamani <thechargingvolcano@gmail.com>
Reviewed-By: Khaidi Chu <i@2333.moe>
---
 test/common/README.md                      |  6 +++++
 test/common/index.js                       | 16 ++++++++++++-
 test/parallel/test-common-must-not-call.js | 26 ++++++++++++++++++++++
 3 files changed, 47 insertions(+), 1 deletion(-)
 create mode 100644 test/parallel/test-common-must-not-call.js

diff --git a/test/common/README.md b/test/common/README.md
index b6cc52b6651924..5e69db69a4673c 100644
--- a/test/common/README.md
+++ b/test/common/README.md
@@ -135,6 +135,12 @@ Path to the 'fixtures' directory.
 
 Returns an instance of all possible `ArrayBufferView`s of the provided Buffer.
 
+### getCallSite(func)
+* `func` [&lt;Function>]
+* return [&lt;String>]
+
+Returns the file name and line number for the provided Function.
+
 ### globalCheck
 * return [&lt;Boolean>]
 
diff --git a/test/common/index.js b/test/common/index.js
index 9798b0fdab8dad..899f5e0acdee21 100644
--- a/test/common/index.js
+++ b/test/common/index.js
@@ -579,9 +579,23 @@ exports.canCreateSymLink = function() {
   return true;
 };
 
+exports.getCallSite = function getCallSite(top) {
+  const originalStackFormatter = Error.prepareStackTrace;
+  Error.prepareStackTrace = (err, stack) =>
+    `${stack[0].getFileName()}:${stack[0].getLineNumber()}`;
+  const err = new Error();
+  Error.captureStackTrace(err, top);
+  // with the V8 Error API, the stack is not formatted until it is accessed
+  err.stack;
+  Error.prepareStackTrace = originalStackFormatter;
+  return err.stack;
+};
+
 exports.mustNotCall = function(msg) {
+  const callSite = exports.getCallSite(exports.mustNotCall);
   return function mustNotCall() {
-    assert.fail(msg || 'function should not have been called');
+    assert.fail(
+      `${msg || 'function should not have been called'} at ${callSite}`);
   };
 };
 
diff --git a/test/parallel/test-common-must-not-call.js b/test/parallel/test-common-must-not-call.js
new file mode 100644
index 00000000000000..d70daabf0a4bd0
--- /dev/null
+++ b/test/parallel/test-common-must-not-call.js
@@ -0,0 +1,26 @@
+'use strict';
+
+const common = require('../common');
+const assert = require('assert');
+const path = require('path');
+
+const message = 'message';
+const testFunction = common.mustNotCall(message);
+
+const validateError = common.mustCall((e) => {
+  const prefix = `${message} at `;
+  assert.ok(e.message.startsWith(prefix));
+  if (process.platform === 'win32') {
+    e.message = e.message.substring(2); // remove 'C:'
+  }
+  const [ fileName, lineNumber ] = e.message
+                                    .substring(prefix.length).split(':');
+  assert.strictEqual(path.basename(fileName), 'test-common-must-not-call.js');
+  assert.strictEqual(lineNumber, '8');
+});
+
+try {
+  testFunction();
+} catch (e) {
+  validateError(e);
+}