Lint with eslint, prettier, airbnb

.eslintignore

@@ -0,0 +1 @@
+!.eslintrc.js

.eslintrc.js

@@ -0,0 +1,25 @@
+module.exports = {
+  extends: [
+    'eslint-config-airbnb-base',
+    'eslint-config-prettier',
+    'plugin:ava/recommended',
+  ],
+  plugins: ['eslint-plugin-prettier', 'eslint-plugin-ava'],
+  env: {
+    commonjs: true,
+    node: true,
+  },
+  rules: {
+    'class-methods-use-this': 'off',
+    'no-shadow': 'off',
+    'no-underscore-dangle': 'off',
+    'prettier/prettier': [
+      'error',
+      {
+        singleQuote: true,
+        trailingComma: 'es5',
+        bracketSpacing: true,
+      },
+    ],
+  },
+};

.travis.yml

@@ -3,13 +3,14 @@ language: node_js
 cache: yarn
 node_js:
 - '6.11.5'
-- '7'
 - '8'
+- '10'
 install:
 - yarn install --frozen-lockfile
 before_install:
 # Required due to: https://github.com/travis-ci/travis-ci/issues/7951
 - curl -sSfL https://yarnpkg.com/install.sh | bash
 - export PATH=$HOME/.yarn/bin:$PATH
 script:
+- yarn lint
 - yarn test

package.json

@@ -17,6 +17,7 @@
   "license": "MPL-2.0",
   "scripts": {
     "test": "ava test",
+    "lint": "eslint src test .eslintrc.js",
     "changelog": "changelog mozilla-neutrino/webpack-chain all --markdown > CHANGELOG.md"
   },
   "dependencies": {
@@ -26,6 +27,13 @@
   "devDependencies": {
     "ava": "^0.25.0",
     "changelog": "^1.4.0",
+    "eslint": "^4.19.1",
+    "eslint-config-airbnb-base": "^12.1.0",
+    "eslint-config-prettier": "^2.9.0",
+    "eslint-plugin-ava": "^4.5.1",
+    "eslint-plugin-import": "^2.11.0",
+    "eslint-plugin-prettier": "^2.6.0",
+    "prettier": "^1.12.1",
     "webpack": "^4.5.0"
   }
 }

src/ChainedMap.js

@@ -9,7 +9,7 @@ module.exports = class extends Chainable {
 
   extend(methods) {
     this.shorthands = methods;
-    methods.map(method => {
+    methods.forEach(method => {
       this[method] = value => this.set(method, value);
     });
     return this;
@@ -58,6 +58,8 @@ module.exports = class extends Chainable {
     if (order.length) {
       return entries;
     }
+
+    return undefined;
   }
 
   values() {
@@ -80,50 +82,57 @@ module.exports = class extends Chainable {
   }
 
   merge(obj, omit = []) {
-    Object
-      .keys(obj)
-      .forEach(key => {
-        if (omit.includes(key)) {
-          return;
-        }
-
-        const value = obj[key];
-
-        if ((!Array.isArray(value) && typeof value !== 'object') || value === null || !this.has(key)) {
-          this.set(key, value);
-        } else {
-          this.set(key, merge(this.get(key), value));
-        }
-      });
+    Object.keys(obj).forEach(key => {
+      if (omit.includes(key)) {
+        return;
+      }
+
+      const value = obj[key];
+
+      if (
+        (!Array.isArray(value) && typeof value !== 'object') ||
+        value === null ||
+        !this.has(key)
+      ) {
+        this.set(key, value);
+      } else {
+        this.set(key, merge(this.get(key), value));
+      }
+    });
 
     return this;
   }
 
   clean(obj) {
-    return Object
-      .keys(obj)
-      .reduce((acc, key) => {
-        const value = obj[key];
+    return Object.keys(obj).reduce((acc, key) => {
+      const value = obj[key];
 
-        if (value === undefined) {
-          return acc;
-        }
+      if (value === undefined) {
+        return acc;
+      }
 
-        if (Array.isArray(value) && !value.length) {
-          return acc;
-        }
+      if (Array.isArray(value) && !value.length) {
+        return acc;
+      }
 
-        if (Object.prototype.toString.call(value) === '[object Object]' && !Object.keys(value).length) {
-          return acc;
-        }
+      if (
+        Object.prototype.toString.call(value) === '[object Object]' &&
+        !Object.keys(value).length
+      ) {
+        return acc;
+      }
 
-        acc[key] = value;
+      acc[key] = value;
 
-        return acc;
-      }, {});
+      return acc;
+    }, {});
   }
 
-  when(condition, whenTruthy = Function.prototype, whenFalsy = Function.prototype) {
+  when(
+    condition,
+    whenTruthy = Function.prototype,
+    whenFalsy = Function.prototype
+  ) {
     if (condition) {
       whenTruthy(this);
     } else {

src/ChainedSet.js

@@ -39,7 +39,11 @@ module.exports = class extends Chainable {
     return this;
   }
 
-  when(condition, whenTruthy = Function.prototype, whenFalsy = Function.prototype) {
+  when(
+    condition,
+    whenTruthy = Function.prototype,
+    whenFalsy = Function.prototype
+  ) {
     if (condition) {
       whenTruthy(this);
     } else {

src/Config.js

@@ -39,7 +39,7 @@ module.exports = class extends ChainedMap {
       'stats',
       'target',
       'watch',
-      'watchOptions'
+      'watchOptions',
     ]);
   }
 
@@ -62,69 +62,76 @@ module.exports = class extends ChainedMap {
   toConfig() {
     const entryPoints = this.entryPoints.entries() || {};
 
-    return this.clean(Object.assign(this.entries() || {}, {
-      node: this.node.entries(),
-      output: this.output.entries(),
-      resolve: this.resolve.toConfig(),
-      resolveLoader: this.resolveLoader.toConfig(),
-      devServer: this.devServer.toConfig(),
-      module: this.module.toConfig(),
-      optimization: this.optimization.entries(),
-      plugins: this.plugins.values().map(plugin => plugin.toConfig()),
-      performance: this.performance.entries(),
-      entry: Object
-        .keys(entryPoints)
-        .reduce((acc, key) => Object.assign(acc, { [key]: entryPoints[key].values() }), {})
-    }));
+    return this.clean(
+      Object.assign(this.entries() || {}, {
+        node: this.node.entries(),
+        output: this.output.entries(),
+        resolve: this.resolve.toConfig(),
+        resolveLoader: this.resolveLoader.toConfig(),
+        devServer: this.devServer.toConfig(),
+        module: this.module.toConfig(),
+        optimization: this.optimization.entries(),
+        plugins: this.plugins.values().map(plugin => plugin.toConfig()),
+        performance: this.performance.entries(),
+        entry: Object.keys(entryPoints).reduce(
+          (acc, key) =>
+            Object.assign(acc, { [key]: entryPoints[key].values() }),
+          {}
+        ),
+      })
+    );
   }
 
-  toString({
-    verbose = false,
-    configPrefix = 'config'
-  } = {}) {
+  toString({ verbose = false, configPrefix = 'config' } = {}) {
+    // eslint-disable-next-line global-require
     const stringify = require('javascript-stringify');
-
     const config = this.toConfig();
 
-    return stringify(config, (value, indent, stringify) => {
-      // improve plugin output
-      if (value && value.__pluginName) {
-        const prefix = `/* ${configPrefix}.plugin('${value.__pluginName}') */\n`;
-        const constructorName = value.__pluginConstructorName;
-
-        if (constructorName) {
-          // get correct indentation for args by stringifying the args array and
-          // discarding the square brackets.
-          const args = stringify(value.__pluginArgs).slice(1, -1);
-          return prefix + `new ${constructorName}(${args})`;
-        } else {
+    return stringify(
+      config,
+      (value, indent, stringify) => {
+        // improve plugin output
+        if (value && value.__pluginName) {
+          const prefix = `/* ${configPrefix}.plugin('${
+            value.__pluginName
+          }') */\n`;
+          const constructorName = value.__pluginConstructorName;
+
+          if (constructorName) {
+            // get correct indentation for args by stringifying the args array and
+            // discarding the square brackets.
+            const args = stringify(value.__pluginArgs).slice(1, -1);
+            return `${prefix}new ${constructorName}(${args})`;
+          }
           return prefix + stringify({ args: value.__pluginArgs || [] });
         }
-      }
 
-      // improve rule/use output
-      if (value && value.__ruleNames) {
-        const prefix = `/* ${configPrefix}.module.rule('${
-          value.__ruleNames[0]
-        }')${
-          value.__ruleNames.slice(1).map(r => `.oneOf('${r}')`).join('')
-        }${
-          value.__useName ? `.use('${value.__useName}')` : ``
-        } */\n`;
-        return prefix + stringify(value);
-      }
+        // improve rule/use output
+        if (value && value.__ruleNames) {
+          const prefix = `/* ${configPrefix}.module.rule('${
+            value.__ruleNames[0]
+          }')${value.__ruleNames
+            .slice(1)
+            .map(r => `.oneOf('${r}')`)
+            .join('')}${
+            value.__useName ? `.use('${value.__useName}')` : ``
+          } */\n`;
+          return prefix + stringify(value);
+        }
 
-      // shorten long functions
-      if (typeof value === 'function') {
-        if (value.__expression) {
-          return value.__expression;
-        } else if (!verbose && value.toString().length > 100) {
-          return `function () { /* omitted long function */ }`;
+        // shorten long functions
+        if (typeof value === 'function') {
+          if (value.__expression) {
+            return value.__expression;
+          } else if (!verbose && value.toString().length > 100) {
+            return `function () { /* omitted long function */ }`;
+          }
         }
-      }
 
-      return stringify(value);
-    }, 2);
+        return stringify(value);
+      },
+      2
+    );
   }
 
   merge(obj = {}, omit = []) {
@@ -136,19 +143,19 @@ module.exports = class extends ChainedMap {
       'devServer',
       'optimization',
       'performance',
-      'module'
+      'module',
     ];
 
     if (!omit.includes('entry') && 'entry' in obj) {
-      Object
-        .keys(obj.entry)
-        .forEach(name => this.entry(name).merge(obj.entry[name]));
+      Object.keys(obj.entry).forEach(name =>
+        this.entry(name).merge(obj.entry[name])
+      );
     }
 
     if (!omit.includes('plugin') && 'plugin' in obj) {
-      Object
-        .keys(obj.plugin)
-        .forEach(name => this.plugin(name).merge(obj.plugin[name]));
+      Object.keys(obj.plugin).forEach(name =>
+        this.plugin(name).merge(obj.plugin[name])
+      );
     }
 
     omissions.forEach(key => {

src/DevServer.js

@@ -1,6 +1,5 @@
 const ChainedMap = require('./ChainedMap');
 const ChainedSet = require('./ChainedSet');
-const merge = require('deepmerge');
 
 module.exports = class extends ChainedMap {
   constructor(parent) {
@@ -44,14 +43,19 @@ module.exports = class extends ChainedMap {
       'stdin',
       'useLocalIp',
       'watchContentBase',
-      'watchOptions'
+      'watchOptions',
     ]);
   }
 
   toConfig() {
-    return this.clean(Object.assign({
-      allowedHosts: this.allowedHosts.values(),
-    }, this.entries() || {}));
+    return this.clean(
+      Object.assign(
+        {
+          allowedHosts: this.allowedHosts.values(),
+        },
+        this.entries() || {}
+      )
+    );
   }
 
   merge(obj, omit = []) {