fix: should not remove eslint-loader on src import blocks (close #1359)

lib/loaders/pitcher.js

@@ -5,6 +5,25 @@ const selfPath = require.resolve('../index')
 const templateLoaderPath = require.resolve('./templateLoader')
 const stylePostLoaderPath = require.resolve('./stylePostLoader')
 
+const isESLintLoader = l => /(\/|\\|@)eslint-loader/.test(l.path)
+const isNullLoader = l => /(\/|\\|@)null-loader/.test(l.path)
+const isCSSLoader = l => /(\/|\\|@)css-loader/.test(l.path)
+const isPitcher = l => l.path !== __filename
+
+const dedupeESLintLoader = loaders => {
+  const res = []
+  let seen = false
+  loaders.forEach(l => {
+    if (!isESLintLoader(l)) {
+      res.push(l)
+    } else if (!seen) {
+      seen = true
+      res.push(l)
+    }
+  })
+  return res
+}
+
 module.exports = code => code
 
 // This pitching loader is responsible for intercepting all vue block requests
@@ -16,17 +35,25 @@ module.exports.pitch = function (remainingRequest) {
 
   let loaders = this.loaders
 
-  // if this is a language block request, remove eslint-loader to avoid
-  // duplicate linting.
+  // if this is a language block request, eslint-loader may get matched
+  // multiple times
   if (query.type) {
-    loaders = loaders.filter(l => !/(\/|\\|@)eslint-loader/.test(l.path))
+    // if this is an inline block, since the whole file itself is being linted,
+    // remove eslint-loader to avoid duplicate linting.
+    if (/\.vue$/.test(this.resourcePath)) {
+      loaders = loaders.filter(l => !isESLintLoader(l))
+    } else {
+      // This is a src import. Just make sure there's not more than 1 instance
+      // of eslint present.
+      loaders = dedupeESLintLoader(loaders)
+    }
   }
 
   // remove self
-  loaders = loaders.filter(l => l.path !== __filename)
+  loaders = loaders.filter(isPitcher)
 
   // do not inject if user uses null-loader to void the type (#1239)
-  if (loaders.some(l => /(\/|\\|@)null-loader/.test(l.path))) {
+  if (loaders.some(isNullLoader)) {
     return
   }
 
@@ -58,7 +85,7 @@ module.exports.pitch = function (remainingRequest) {
 
   // Inject style-post-loader before css-loader for scoped CSS and trimming
   if (query.type === `style`) {
-    const cssLoaderIndex = loaders.findIndex(l => /(\/|\\|@)css-loader/.test(l.path))
+    const cssLoaderIndex = loaders.findIndex(isCSSLoader)
     if (cssLoaderIndex > -1) {
       const afterLoaders = loaders.slice(0, cssLoaderIndex + 1)
       const beforeLoaders = loaders.slice(cssLoaderIndex + 1)