feat(config): instrumenter override option

Enable fine-tuning which preprocessor should be used for which files
Add README.md section
Add tests
Update existing tests to comply with new dependency requirement

Author: gvarsanyi

README.md

@@ -65,7 +65,8 @@ module.exports = function(config) {
     preprocessors: {
       // source files, that you wanna generate coverage for
       // do not include tests or libraries
-      // (these files will be instrumented by Istanbul via Ibrik)
+      // (these files will be instrumented by Istanbul via Ibrik unless
+      // specified otherwise in coverageReporter.instrumenter)
       'src/*.coffee': ['coverage'],
 
       // note: project files will already be converted to
@@ -127,6 +128,27 @@ coverageReporter: {
 }
 ```
 
+#### instrumenter
+Karma-coverage infers the instrumenter regarding of the file extension.
+  The .coffee files are by default covered using
+  [Ibrik](https://github.com/Constellation/ibrik) (an
+  [Istanbul](https://github.com/gotwarlost/istanbul) analog for
+  CoffeeScript files). It is possible to override this behavior and point out an
+  instrumenter for the files matching a specific pattern.
+  To do so, you need to declare an object under with the keys representing the
+  pattern to match, and the instrumenter to apply. The matching will be done
+  using [minimatch](https://github.com/isaacs/minimatch).
+  If two patterns match, the last one will take the precedence.
+
+```javascript
+coverageReporter: {
+  instrumenter: {
+    '**/*.coffee': 'istanbul' // Force the use of the Istanbul instrumenter to cover CoffeeScript files
+  },
+  // ...
+}
+```
+
 ----
 
 For more information on Karma see the [homepage].

lib/preprocessor.js

@@ -1,10 +1,11 @@
-var istanbul = require('istanbul'),
-    ibrik    = require('ibrik');
+var istanbul  = require('istanbul'),
+    ibrik     = require('ibrik'),
+    minimatch = require('minimatch');
 
-var createCoveragePreprocessor = function(logger, basePath, reporters) {
+var createCoveragePreprocessor = function(logger, basePath, reporters, coverageReporter) {
   var log = logger.create('preprocessor.coverage');
-  var jsInstrumenter = new istanbul.Instrumenter();
-  var coffeeInstrumenter = new ibrik.Instrumenter();
+  var instrumenterOverrides = coverageReporter.instrumenter || {};
+  var instrumenters = {istanbul: istanbul, ibrik: ibrik};
 
   // if coverage reporter is not used, do not preprocess the files
   if (reporters.indexOf('coverage') === -1) {
@@ -13,23 +14,55 @@ var createCoveragePreprocessor = function(logger, basePath, reporters) {
     };
   }
 
+  // check instrumenter override requests
+  function checkInstrumenters() {
+    var literal;
+    for (var pattern in instrumenterOverrides) {
+      literal = String(instrumenterOverrides[pattern]).toLowerCase();
+      if (literal !== 'istanbul' && literal !== 'ibrik') {
+        log.error('Unknown instrumenter: %s', literal);
+        return false;
+      }
+    }
+    return true;
+  }
+  if (!checkInstrumenters()) {
+    return function(content, _, done) {
+      return done(1);
+    };
+  }
+
   return function(content, file, done) {
     log.debug('Processing "%s".', file.originalPath);
 
     var jsPath = file.originalPath.replace(basePath + '/', './');
-    var instrumenter = jsPath.match(/\.coffee$/) ? coffeeInstrumenter : jsInstrumenter;
+    var instrumenterLiteral = jsPath.match(/\.coffee$/) ? 'ibrik' : 'istanbul';
+
+    for (var pattern in instrumenterOverrides) {
+      if (minimatch(file.originalPath, pattern, {dot: true})) {
+        instrumenterLiteral = String(instrumenterOverrides[pattern]).toLowerCase();
+      }
+    }
+
+    var instrumenter = new instrumenters[instrumenterLiteral].Instrumenter();
 
     instrumenter.instrument(content, jsPath, function(err, instrumentedCode) {
-      if(err) {
+      if (err) {
         log.error('%s\n  at %s', err.message, file.originalPath);
       }
 
-      file.path = file.path.replace(/\.coffee$/, '.js');
+      if (instrumenterLiteral === 'ibrik') {
+        file.path = file.path.replace(/\.coffee$/, '.js');
+      }
+
       done(instrumentedCode);
     });
   };
 };
 
-createCoveragePreprocessor.$inject = ['logger', 'config.basePath', 'config.reporters'];
+createCoveragePreprocessor.$inject = ['logger',
+                                      'config.basePath',
+                                      'config.reporters',
+                                      'config.coverageReporter'];
 
 module.exports = createCoveragePreprocessor;

package.json

@@ -19,9 +19,10 @@
   ],
   "author": "SATO taichi <ryushi@gmail.com>",
   "dependencies": {
+    "dateformat": "~1.0.6",
+    "ibrik": "~1.1.1",
     "istanbul": "~0.2.3",
-    "ibrik":  "~1.1.1",
-    "dateformat": "~1.0.6"
+    "minimatch": "~0.3.0"
   },
   "peerDependencies": {
     "karma": ">=0.9"

test/preprocessor.spec.coffee

@@ -35,7 +35,7 @@ describe 'preprocessor', ->
 
 
   it 'should not do anything if coverage reporter is not used', (done) ->
-    process = createPreprocessor mockLogger, null, ['dots', 'progress']
+    process = createPreprocessor mockLogger, null, ['dots', 'progress'], {}
     file = new File '/base/path/file.js'
 
     process ORIGINAL_CODE, file, (preprocessedCode) ->
@@ -45,7 +45,7 @@ describe 'preprocessor', ->
 
 
   it 'should preprocess the code', (done) ->
-    process = createPreprocessor mockLogger, '/base/path', ['coverage', 'progress']
+    process = createPreprocessor mockLogger, '/base/path', ['coverage', 'progress'], {}
     file = new File '/base/path/file.js'
 
     process ORIGINAL_CODE, file, (preprocessedCode) ->
@@ -58,7 +58,7 @@ describe 'preprocessor', ->
       done()
 
   it 'should preprocess the coffee code', (done) ->
-    process = createPreprocessor mockLogger, '/base/path', ['coverage', 'progress']
+    process = createPreprocessor mockLogger, '/base/path', ['coverage', 'progress'], {}
     file = new File '/base/path/file.coffee'
 
     process ORIGINAL_COFFEE_CODE, file, (preprocessedCode) ->
@@ -70,3 +70,27 @@ describe 'preprocessor', ->
       expect(file.path).to.equal '/base/path/file.js'
       expect(sandbox.__coverage__).to.have.ownProperty './file.coffee'
       done()
+
+  it 'should not preprocess the coffee code', (done) ->
+    process = createPreprocessor mockLogger, '/base/path', ['coverage', 'progress'],
+      instrumenter:
+        '**/*.coffee': 'istanbul'
+    file = new File '/base/path/file.coffee'
+
+    process ORIGINAL_CODE, file, (preprocessedCode) ->
+      sandbox =
+        a: true
+        something: ->
+
+      vm.runInNewContext preprocessedCode, sandbox
+      expect(file.path).to.equal '/base/path/file.coffee'
+      expect(sandbox.__coverage__).to.have.ownProperty './file.coffee'
+      done()
+
+  it 'should fail if invalid instrumenter provided', (done) ->
+    work = ->
+      createPreprocessor mockLogger, '/base/path', ['coverage', 'progress'],
+        instrumenter:
+          '**/*.coffee': 'madeup'
+    expect(work).to.throw()
+    done()