From 47c641f7560d28e0d9eac7ae010566d296d5b628 Mon Sep 17 00:00:00 2001
From: Vojta Jina <vojta.jina@gmail.com>
Date: Thu, 27 Jun 2013 18:59:53 -0700
Subject: [PATCH] fix(preprocessor): do not show duplicate warnings

---
 lib/preprocessor.js | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/lib/preprocessor.js b/lib/preprocessor.js
index 40430ddfa..b7b1a41b2 100644
--- a/lib/preprocessor.js
+++ b/lib/preprocessor.js
@@ -11,9 +11,10 @@ var sha1 = function(data) {
   return hash.digest('hex');
 };
 
-
+// TODO(vojta): instantiate preprocessors at the start to show warnings immediately
 var createPreprocessor = function(config, basePath, injector) {
   var patterns = Object.keys(config);
+  var alreadyDisplayedWarnings = Object.create(null);
 
   return function(file, done) {
     var preprocessors = [];
@@ -27,16 +28,21 @@ 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) {
-        // TODO(vojta): log warning only once per each preprocessor
         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;
       }
     };