make js default loader check work when npm-linked

Author: yyx990803

lib/loader.js

@@ -2,9 +2,10 @@ var path = require('path')
 var hash = require('hash-sum')
 var parse = require('./parser')
 var genId = require('./utils/gen-id')
-var normalize = require('./utils/normalize')
-var loaderUtils = require('loader-utils')
 var querystring = require('querystring')
+var loaderUtils = require('loader-utils')
+var normalize = require('./utils/normalize')
+var hasLoader = require('./utils/has-loader')
 
 // internal lib loaders
 var selectorPath = normalize.lib('selector')
@@ -17,15 +18,9 @@ var componentNormalizerPath = normalize.lib('component-normalizer')
 var styleLoaderPath = normalize.dep('vue-style-loader')
 var hotReloadAPIPath = normalize.dep('vue-hot-reload-api')
 
-var hasBabel = false
-try {
-  hasBabel = !!require('babel-loader')
-} catch (e) {}
-
-var hasBuble = false
-try {
-  hasBuble = !!require('buble-loader')
-} catch (e) {}
+// check whether default js loader exists
+var hasBabel = hasLoader('babel')
+var hasBuble = hasLoader('buble')
 
 var rewriterInjectRE = /\b(css(?:-loader)?(?:\?[^!]+)?)(?:!|$)/
 

lib/utils/has-loader.js

@@ -0,0 +1,15 @@
+var fs = require('fs')
+var path = require('path')
+var cwd = process.cwd()
+
+module.exports = function (loader) {
+  loader += '-loader'
+  var hasLoader = false
+  try {
+    hasLoader = !!require(loader)
+  } catch (e) {}
+  if (!hasLoader) {
+    hasLoader = fs.existsSync(path.resolve(cwd, 'node_modules', loader))
+  }
+  return hasLoader
+}