Restore code coverage in Karma config

The transpiling step is done by babel instead of bublé now.
Bublé caused the istanbul instrumenter step to crash because of an
unexpected SourceMap object format.

.circleci/config.yml

@@ -27,6 +27,10 @@ jobs:
           name: Run Tests
           command: npm test
 
+      - store_artifacts:
+          path: coverage/
+          destination: coverage
+
       - store_artifacts:
           path: rendering/cases/
           destination: rendering

package.json

@@ -41,12 +41,15 @@
     "rbush": "2.0.2"
   },
   "devDependencies": {
+    "@babel/core": "^7.4.0",
+    "@babel/preset-env": "^7.4.2",
     "@openlayers/eslint-plugin": "^4.0.0-beta.2",
     "@types/arcgis-rest-api": "^10.4.4",
     "@types/geojson": "^7946.0.7",
     "@types/pbf": "^3.0.1",
     "@types/rbush": "^2.0.2",
     "@types/topojson-specification": "^1.0.1",
+    "babel-loader": "^8.0.5",
     "buble": "^0.19.7",
     "buble-loader": "^0.5.1",
     "chaikin-smooth": "^1.0.4",
@@ -63,12 +66,14 @@
     "handlebars": "4.1.2",
     "html-to-image": "^0.1.0",
     "istanbul": "0.4.5",
+    "istanbul-instrumenter-loader": "^3.0.1",
     "jquery": "3.4.1",
     "jsdoc": "3.5.5",
     "jsdoc-plugin-typescript": "^1.0.8",
     "karma": "^4.0.1",
     "karma-chrome-launcher": "2.2.0",
     "karma-coverage": "^1.1.2",
+    "karma-coverage-istanbul-reporter": "^2.0.5",
     "karma-firefox-launcher": "^1.1.0",
     "karma-mocha": "1.3.0",
     "karma-sourcemap-loader": "^0.3.7",

test/karma.config.js

@@ -2,6 +2,7 @@ const path = require('path');
 
 module.exports = function(karma) {
   karma.set({
+    browsers: ['Chrome'],
     browserDisconnectTolerance: 2,
     frameworks: ['mocha'],
     client: {
@@ -54,7 +55,12 @@ module.exports = function(karma) {
     preprocessors: {
       '**/*.js': ['webpack', 'sourcemap']
     },
-    reporters: ['dots'],
+    reporters: ['dots', 'coverage-istanbul'],
+    coverageIstanbulReporter: {
+      reports: ['text-summary', 'html'],
+      dir: path.resolve(__dirname, '../coverage/'),
+      fixWebpackSourcePaths: true
+    },
     webpack: {
       devtool: 'inline-source-map',
       mode: 'development',
@@ -63,8 +69,23 @@ module.exports = function(karma) {
           {
             test: /\.js$/,
             use: {
-              loader: 'buble-loader'
-            }
+              loader: 'babel-loader',
+              options: {
+                presets: ['@babel/preset-env']
+              }
+            },
+            include: path.resolve('src/ol/'),
+            exclude: path.resolve('node_modules/')
+          }, {
+            test: /\.js$/,
+            use: {
+              loader: 'istanbul-instrumenter-loader',
+              options: {
+                esModules: true
+              }
+            },
+            include: path.resolve('src/ol/'),
+            exclude: path.resolve('node_modules/')
           }
         ]
       }
@@ -75,28 +96,4 @@ module.exports = function(karma) {
   });
 
   process.env.CHROME_BIN = require('puppeteer').executablePath();
-  if (process.env.CIRCLECI) {
-    karma.set({
-      browsers: ['Chrome'],
-      preprocessors: {
-        '../src/**/*.js': ['coverage']
-      },
-      coverageReporter: {
-        reporters: [
-          {
-            type: 'lcovonly', // that's enough for coveralls, no HTML
-            dir: '../coverage/',
-            subdir: '.'
-          },
-          {
-            type: 'text-summary' // prints the textual summary to the terminal
-          }
-        ]
-      }
-    });
-  } else {
-    karma.set({
-      browsers: ['Chrome']
-    });
-  }
 };