feat: make __file injection opt-in in production (#1475)

Author: haoqunjiang

Diff for: docs/options.md

@@ -92,3 +92,12 @@ When both options are specified, enables file-system-based template compilation
 - default: `true`
 
 In development mode, we use [prettier](https://prettier.io/) to format the compiled render function for ease of debugging by default. However, if you encounter any obscure bug of prettier, such as [exponential compilation time for deeply nested functions](https://github.com/prettier/prettier/issues/4672), you can disable this option to circumvent it.
+
+## exposeFilename
+
+- type: `boolean`
+- default: `false`
+
+In non-production environments, vue-loader injects a `__file` property to components for better debugging experience. If the `name` property is missing in a component, Vue will infer it from the `__file` field to display in console warnings.
+
+This property is stripped in production builds by default. But you may want to retain it if you are developing a component library and don't want to bother specifying `name` in each component. Then you can turn this option on.

Diff for: lib/index.js

@@ -176,14 +176,15 @@ var component = normalizer(
   }
 
   // Expose filename. This is used by the devtools and Vue runtime warnings.
-  code += `\ncomponent.options.__file = ${
-    isProduction
-      // For security reasons, only expose the file's basename in production.
-      ? JSON.stringify(filename)
-      // Expose the file's full path in development, so that it can be opened
-      // from the devtools.
-      : JSON.stringify(rawShortFilePath.replace(/\\/g, '/'))
-  }`
+  if (!isProduction) {
+    // Expose the file's full path in development, so that it can be opened
+    // from the devtools.
+    code += `\ncomponent.options.__file = ${JSON.stringify(rawShortFilePath.replace(/\\/g, '/'))}`
+  } else if (options.exposeFilename) {
+    // Libraies can opt-in to expose their components' filenames in production builds.
+    // For security reasons, only expose the file's basename in production.
+    code += `\ncomponent.options.__file = ${JSON.stringify(filename)}`
+  }
 
   code += `\nexport default component.exports`
   // console.log(code)

Diff for: test/advanced.spec.js

@@ -54,13 +54,31 @@ test('expose file path as __file outside production', done => {
   })
 })
 
-test('expose file basename as __file in production', done => {
+test('no __file in production when exposeFilename disabled', done => {
   const origNodeEnv = process.env.NODE_ENV
   process.env.NODE_ENV = 'production'
   mockBundleAndRun(
     {
       entry: 'basic.vue'
     },
+    ({ module }) => {
+      expect(module.__file).toBe(undefined)
+      process.env.NODE_ENV = origNodeEnv
+      done()
+    }
+  )
+})
+
+test('expose file basename as __file in production when exposeFilename enabled', done => {
+  const origNodeEnv = process.env.NODE_ENV
+  process.env.NODE_ENV = 'production'
+  mockBundleAndRun(
+    {
+      entry: 'basic.vue',
+      vue: {
+        exposeFilename: true
+      }
+    },
     ({ module }) => {
       expect(module.__file).toBe('basic.vue')
       process.env.NODE_ENV = origNodeEnv