Core: Fix stacktrace cleaner to support URLs with host ports

Fixes #1769.

src/core/stacktrace.js

@@ -1,10 +1,45 @@
-// See also https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Error/Stack
+// Stacktrace cleaner to focus on the path from error source to test suite.
+//
+// This should reduce a raw stack trace like this:
+//
+// > foo.broken()@/src/foo.js
+// > Bar@/src/bar.js
+// > @/test/bar.test.js
+// > @/lib/qunit.js:500:12
+// > @/lib/qunit.js:100:28
+// > @/lib/qunit.js:200:56
+// > setTimeout@
+// > @/dist/vendor.js
+//
+// and shorten it to show up until the end of the user's bar.test.js code.
+//
+// > foo.broken()@/src/foo.js
+// > Bar@/src/bar.js
+// > @/test/bar.test.js
+//
+// QUnit will obtain one example trace (once per process/pageload suffices),
+// strip off any :<line> and :<line>:<column>, and use that as match needle,
+// to the first QUnit-internal frames, and then stop at that point.
+// Any later frames, including those that are outside QUnit again, will be ommitted
+// as being uninteresting to the test, since QUnit will have either started or
+// resumed the test. This we also clean away browser built-ins, or other
+// vendor/bundler that may be higher up the stack.
+//
+// Stripping :<line>:<column> is not for prettyness, it is essential for the
+// match needle to work, since this sample trace will by definitin not be the
+// same line as e.g. the QUnit.test() call we're trying to identify.
+//
+// See also:
+// - https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Error/Stack
+//
 const fileName = (sourceFromStacktrace(0) || '')
-  .replace(/(:\d+)+\)?/, '')
-  // Remove anything prior to the last slash (Unix/Windows)
-  // from the last frame
+  // Global replace, because a frame like localhost:4000/lib/qunit.js:1234:50,
+  // would otherwise (harmlessly, but uselessly) remove only the port (first match).
+  // https://github.com/qunitjs/qunit/issues/1769
+  .replace(/(:\d+)+\)?/g, '')
+  // Remove anything prior to the last slash (Unix/Windows) from the last frame,
+  // leaving only "qunit.js".
   .replace(/.+[/\\]/, '');
-
 export function extractStacktrace (e, offset) {
   offset = offset === undefined ? 4 : offset;
 

test/main/stacktrace.js

@@ -27,7 +27,13 @@
     assert.pushResult({
       result: simple.indexOf('/main/stacktrace.js') !== -1,
       actual: simple,
-      message: 'current file'
+      message: 'include current file'
+    });
+    assert.pushResult({
+      result: simple.indexOf('qunit.js') === -1,
+      actual: simple,
+      expected: 'NOT qunit.js',
+      message: 'stacktrace cleaning stops before qunit.js'
     });
 
     var nested = norm(fooParent());