fix: coverage yields empty reports (#246)

* fix: make use of istanbul-instrumenter-loader to get correct coverage

It is important to note that this is version 0.2.0 of the module.
Versions after that does not support the html and lcov reporters
(lcovonly is supported).

* fix: istanbul-instrumenter-loader for JS enforces pre not post

* refactor to use webpack-chain

* tweaks

packages/poi-preset-karma/README.md

@@ -28,6 +28,8 @@ Then run `poi test`, this preset will only be activated in test mode.
 
 Or run `poi test --watch` to run Karma in watch mode.
 
+Or run `poi test --coverage` to get code coverage as well.
+
 ## Options
 
 ### port

packages/poi-preset-karma/index.js

@@ -13,17 +13,48 @@ module.exports = (options = {}) => {
       poi.extendWebpack(options.extendWebpack)
     }
 
-    poi.run('test', webpackConfig => {
-      const inferValue = (key, fallback) => {
-        if (typeof poi.argv[key] !== 'undefined') {
-          return poi.argv[key]
-        }
-        if (typeof options[key] !== 'undefined') {
-          return options[key]
-        }
-        return fallback
+    const inferValue = (key, fallback) => {
+      if (typeof poi.argv[key] !== 'undefined') {
+        return poi.argv[key]
+      }
+      if (typeof options[key] !== 'undefined') {
+        return options[key]
       }
+      return fallback
+    }
 
+    poi.extendWebpack('test', config => {
+      const coverage = inferValue('coverage')
+
+      if (coverage) {
+        /* for general usage */
+        config.module.rule('istanbul-instrumenter-loader')
+          .test(/\.(jsx?)$/)
+          .exclude
+            .add(/(node_modules|\.test\.jsx?)/)
+            .end()
+          .pre()
+          .use('istanbul-instrumenter-loader')
+            .loader('istanbul-instrumenter-loader')
+            .options({
+              esModules: true
+            })
+
+        /* for vue (assumes vue-loader) */
+        config.module.rule('vue')
+          .use('vue-loader')
+          .tap(vueOptions => {
+            const instrumenterLoader = 'istanbul-instrumenter-loader?esModules=true'
+            vueOptions.preLoaders = (vueOptions.preLoaders || {})
+            vueOptions.preLoaders.js = typeof vueOptions.preLoaders.js === 'string' ?
+              `${vueOptions.preLoaders.js}!${instrumenterLoader}` :
+              instrumenterLoader
+            return vueOptions
+          })
+      }
+    })
+
+    poi.run('test', webpackConfig => {
       let files = inferValue('files', ['test/unit/**/*.test.js'])
       files = ensureArray(files)
       files.push({ pattern: 'static/**/*', watched: false, included: false, served: true, nocache: false })
@@ -34,13 +65,12 @@ module.exports = (options = {}) => {
       frameworks = ensureArray(frameworks)
 
       const watch = inferValue('watch', false)
+      const coverage = inferValue('coverage')
 
       const defaultBrowser = inferValue('headless') ? 'ChromeHeadless' : 'Chrome'
       let browsers = inferValue('browsers') || defaultBrowser
       browsers = ensureArray(browsers)
 
-      const coverage = inferValue('coverage')
-
       const defaultConfig = {
         port,
         frameworks,
@@ -50,20 +80,15 @@ module.exports = (options = {}) => {
         reporters: ['mocha'].concat(coverage ? ['coverage'] : []),
         coverageReporter: {
           dir: 'coverage',
-          reporters: [{
-            type: 'html',
-            subdir: 'report-html'
-          }, {
-            type: 'lcov',
-            subdir: 'report-lcov'
-          }]
+          reporters: [
+            { type: 'text' },
+            { type: 'html', subdir: 'report-html' },
+            { type: 'lcov', subdir: 'report-lcov' }
+          ]
         },
         preprocessors: files.reduce((current, next) => {
-          if (typeof next === 'object' && next.included !== false) {
-            current[next.pattern] = ['webpack', 'sourcemap']
-          } else if (typeof next === 'string') {
-            current[next] = ['webpack', 'sourcemap']
-          }
+          const key = typeof next === 'object' && next.included !== false ? next.pattern : next
+          current[key] = ['webpack']
           return current
         }, {}),
         webpackMiddleware: {

packages/poi-preset-karma/package.json

@@ -8,6 +8,7 @@
     "index.js"
   ],
   "dependencies": {
+    "istanbul-instrumenter-loader": "^3.0.0",
     "jasmine-core": "^2.8.0",
     "karma": "^1.7.1",
     "karma-chrome-launcher": "^2.2.0",