Karma 2 no longer correctly reports the original error stack when using source maps

[doberkofler]

Expected behavior

When reporting an error and source maps are available the error stack should point to the original source line and column. The mocha-reporter shows this by using a format like in the following example:
(webpack:///test/unittest/frontend/ods/convert--test.js:43:9 <- temp/karma_unittests/convert--test.js:712:10)

at Context.<anonymous> (webpack:///test/unittest/frontend/ods/convert--test.js:43:9 <- temp/karma_unittests/convert--test.js:712:10)

Actual behavior

Up to Karma 1.7 this worked as expected but starting with Karma 2.0 the commit made a change in the definition of URL_REGEXP that causes the reporter to no longer recognize the lines in the error stack.
In the file lib/reporter.js when building URL_REGEXP the urlRoot + '\\/?' is now added before the (base/|absolute) and because urlRoot is always automatically post fixed with / the resulting regular expression now expects the url always to start with /base causing the matching to fail and to no longer correctly report the original file, line and column of the error stack.

at Context.<anonymous> (base/temp/karma_unittests/convert--test.js?6c85b6986d1a9cc153d2877ce8637a38a6b666ad:712:10)

Environment Details

• Karma version (output of karma --version): 2.0.0
• Relevant part of your karma.config.js file

// Karma configuration

module.exports = function(config) {
  config.set({
    // base path that will be used to resolve all patterns (eg. files, exclude)
    basePath: '',

	// frameworks to use
    // available frameworks: https://npmjs.org/browse/keyword/karma-adapter
    frameworks: ['mocha', 'chai'],

    // list of files / patterns to load in the browser
    files: [
      'dist/**/*.js'
    ],

    // list of files to exclude
    exclude: [
    ],

    // preprocess matching files before serving them to the browser
    // available preprocessors: https://npmjs.org/browse/keyword/karma-preprocessor
    preprocessors: {
		'dist/**/*.js': ['sourcemap']
    },

    // test results reporter to use
    // possible values: 'dots', 'progress'
    // available reporters: https://npmjs.org/browse/keyword/karma-reporter
    reporters: ['mocha'],

    // reporter options
    mochaReporter: {
      showDiff: true
  	},

    // web server port
    port: 9876,

    // enable / disable colors in the output (reporters and logs)
    colors: true,

    // level of logging
    // possible values: config.LOG_DISABLE || config.LOG_ERROR || config.LOG_WARN || config.LOG_INFO || config.LOG_DEBUG
    logLevel: config.LOG_DEBUG,

    // enable / disable watching file and executing tests whenever any file changes
    autoWatch: false,

    // start these browsers
    // available browser launchers: https://npmjs.org/browse/keyword/karma-launcher
    browsers: ['Chrome'/*, 'Firefox', 'IE'*/],

    // Continuous Integration mode
    // if true, Karma captures browsers, runs the tests and exits
    singleRun: true,

    // Concurrency level
    // how many browser should be started simultaneous
    concurrency: 1,

	client: {
		// Capture all console output and pipe it to the terminal.
		captureConsole: true,
		mocha: {
			timeout: 60000
		}
	},

  });
}

Steps to reproduce the behavior

1. Build a mocha unit test with a failing test and bundle it using webpack
2. Run the unit test using karma
3. Compare the results of the error stack between Karma 1.7 and 2.0

[andsouto]

I'm having exactly the same problem after upgrading to karma 2.0 and #2931 fixed the problem for me. What prevents it to be merged?

[lusarz]

I confirm this issue. Here I prepared minimal reproduction. To reproduce:

npm install
npm run test

then

npm install karma@1.7
npm run test

[Cobertos]

Can confirm that reverting to karma@1.7.1 works on my project and that karma@2.0.0 is the issue