feat(preprocessor): Instantiate preprocessors early to avoid race con…

…ditions

lib/preprocessor.js

@@ -17,14 +17,39 @@ extensions.forEach(function (extension) {
   isBinary['.' + extension] = true
 })
 
-// TODO(vojta): instantiate preprocessors at the start to show warnings immediately
 var createPreprocessor = function (config, basePath, injector) {
-  var alreadyDisplayedWarnings = Object.create(null)
+  var alreadyDisplayedWarnings = {}
+  var instances = {}
+  var patterns = Object.keys(config)
 
-  return function (file, done) {
-    var patterns = Object.keys(config)
+  var instantiatePreprocessor = function (name) {
+    if (alreadyDisplayedWarnings[name]) {
+      return
+    }
+
+    try {
+      instances[name] = 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)
+      } else {
+        log.warn('Can not load "%s"!\n  ' + e.stack, name)
+      }
+
+      alreadyDisplayedWarnings[name] = true
+    }
+  }
+
+  patterns.forEach(function (pattern) {
+    config[pattern].forEach(instantiatePreprocessor)
+  })
+
+  return function preprocess (file, done) {
+    patterns = Object.keys(config)
     var thisFileIsBinary = isBinary[path.extname(file.originalPath)]
     var preprocessors = []
+
     var nextPreprocessor = function (error, content) {
       // normalize B-C
       if (arguments.length === 1 && typeof error === 'string') {
@@ -47,34 +72,19 @@ var createPreprocessor = function (config, basePath, injector) {
 
       preprocessors.shift()(content, file, nextPreprocessor)
     }
-    var instantiatePreprocessor = function (name) {
-      if (alreadyDisplayedWarnings[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)
-        } else {
-          log.warn('Can not load "%s"!\n  ' + e.stack, name)
-        }
-
-        alreadyDisplayedWarnings[name] = true
-      }
-    }
 
-    // collects matching preprocessors
-    // TODO(vojta): should we cache this ?
     for (var i = 0; i < patterns.length; i++) {
       if (mm(file.originalPath, patterns[i])) {
         if (thisFileIsBinary) {
           log.warn('Ignoring preprocessing (%s) %s because it is a binary file.',
             config[patterns[i]].join(', '), file.originalPath)
         } else {
-          config[patterns[i]].forEach(instantiatePreprocessor)
+          config[patterns[i]].forEach(function (name) {
+            if (!instances[name]) {
+              instantiatePreprocessor(name)
+            }
+            preprocessors.push(instances[name])
+          })
         }
       }
     }