feat: Fail on launcher-, reporter-, or preprocessor-load errors.

Fail out of karma if a launcher, reporter, or preprocessor fails to
load, after attempting to load each of them, and reporting errors for
each load error.

This is a WIP: I can't quite figure out where to place a final check on
whether any errors were caught while loading launchers, reporters, or
preprocessors. Any quick tip would be much appreciated!

Closes #855

lib/launcher.js

@@ -58,12 +58,13 @@ var Launcher = function(emitter, injector) {
         browser = injector.createChild([locals], ['launcher:' + name]).get('launcher:' + name);
       } catch (e) {
         if (e.message.indexOf('No provider for "launcher:' + name + '"') !== -1) {
-          log.warn('Can not load "%s", it is not registered!\n  ' +
-                   'Perhaps you are missing some plugin?', name);
+          log.error('Can not load "%s", it is not registered!\n  ' +
+                    'Perhaps you are missing some plugin?', name);
         } else {
-          log.warn('Can not load "%s"!\n  ' + e.stack, name);
+          log.error('Can not load "%s"!\n  ' + e.stack, name);
         }
 
+        emitter.emit('load_error', 'launcher', name);
         return;
       }
 

lib/preprocessor.js

@@ -29,9 +29,9 @@ var isBinary = Object.create(null);
 });
 
 // TODO(vojta): instantiate preprocessors at the start to show warnings immediately
-var createPreprocessor = function(config, basePath, injector) {
+var createPreprocessor = function(config, basePath, injector, emitter) {
   var patterns = Object.keys(config);
-  var alreadyDisplayedWarnings = Object.create(null);
+  var alreadyDisplayedErrors = Object.create(null);
 
   return function(file, done) {
     var thisFileIsBinary = isBinary[path.extname(file.originalPath)];
@@ -58,21 +58,22 @@ var createPreprocessor = function(config, basePath, injector) {
       preprocessors.shift()(content, file, nextPreprocessor);
     };
     var instantiatePreprocessor = function(name) {
-      if (alreadyDisplayedWarnings[name]) {
+      if (alreadyDisplayedErrors[name]) {
         return;
       }
 
       try {
         preprocessors.push(injector.get('preprocessor:' + name));
       } catch (e) {
         if (e.message.indexOf('No provider for "preprocessor:' + name + '"') !== -1) {
-          log.warn('Can not load "%s", it is not registered!\n  ' +
-                   'Perhaps you are missing some plugin?', name);
+          log.error('Can not load "%s", it is not registered!\n  ' +
+                    'Perhaps you are missing some plugin?', name);
         } else {
-          log.warn('Can not load "%s"!\n  ' + e.stack, name);
+          log.error('Can not load "%s"!\n  ' + e.stack, name);
         }
 
-        alreadyDisplayedWarnings[name] = true;
+        emitter.emit('load_error', 'preprocessor', name);
+        alreadyDisplayedErrors[name] = true;
       }
     };
 
@@ -98,6 +99,6 @@ var createPreprocessor = function(config, basePath, injector) {
     });
   };
 };
-createPreprocessor.$inject = ['config.preprocessors', 'config.basePath', 'injector'];
+createPreprocessor.$inject = ['config.preprocessors', 'config.basePath', 'injector', 'emitter'];
 
 exports.createPreprocessor = createPreprocessor;

lib/reporter.js

@@ -85,11 +85,13 @@ var createReporters = function(names, config, emitter, injector) {
       reporters.push(injector.createChild([locals], ['reporter:' + name]).get('reporter:' + name));
     } catch (e) {
       if (e.message.indexOf('No provider for "reporter:' + name + '"') !== -1) {
-        log.warn('Can not load "%s", it is not registered!\n  ' +
-                 'Perhaps you are missing some plugin?', name);
+        log.error('Can not load "%s", it is not registered!\n  ' +
+                  'Perhaps you are missing some plugin?', name);
       } else {
-        log.warn('Can not load "%s"!\n  ' + e.stack, name);
+        log.error('Can not load "%s"!\n  ' + e.stack, name);
       }
+
+      emitter.emit('load_error', 'reporter', name);
     }
   });
 

lib/server.js

@@ -27,6 +27,11 @@ var log = logger.create();
 var start = function(injector, config, launcher, globalEmitter, preprocess, fileList, webServer,
     capturedBrowsers, socketServer, executor, done) {
 
+  var loadErrors = [];
+  globalEmitter.on('load_error', function(type, name) {
+    loadErrors.push([type, name]);
+  });
+
   config.frameworks.forEach(function(framework) {
     injector.get('framework:' + framework);
   });