Add eslint using the airbnb config. (#2905)

* Add eslint using the airbnb config.

In an effort to make the JS consistent, this adds an ESLint gulp task. ESLint
is *very* configurable, and has no defaults. Instead, this reaches for
airbnb's legacy config (which covers ES5), which is one of the most popular
configurations. As a last step, it turns off all of the rules which currently
fail. We can turn them on piecemeal, or override the airbnb style to use a
different format.

Rules to prioritize (as they likely indicate bugs):
* "array-callback-return": "off",
* "eqeqeq": "off",
* "guard-for-in": "off",
* "no-inner-declarations": "off",
* "no-loop-func": "off",
* "no-mixed-operators": "off",
* "no-undef": "off",
* "no-use-before-define": "off",
* "one-var": "off",

* Lint frontend in Travis.

This adds an ESLint step to the CI service so we prevent unlinted code from
making its way in.

* Create an ESLint tox env.

By adding a tox env for eslint, we allow users to run it locally as part of
tox runs.

Thanks for the suggestion @ericholscher!

* Fix tox call to gulp lint task

.eslintrc

@@ -0,0 +1,42 @@
+{
+  "extends": "airbnb-base/legacy",
+  "globals": {
+    "$": true
+  },
+  "rules": {
+    "array-callback-return": "off",
+    "brace-style": "off",
+    "camelcase": "off",
+    "comma-dangle": "off",
+    "consistent-return": "off",
+    "dot-notation": "off",
+    "eqeqeq": "off",
+    "func-names": "off",
+    "guard-for-in": "off",
+    "indent": "off",
+    "keyword-spacing": "off",
+    "no-console": "off",
+    "no-inner-declarations": "off",
+    "no-loop-func": "off",
+    "no-mixed-operators": "off",
+    "no-multi-assign": "off",
+    "no-param-reassign": "off",
+    "no-redeclare": "off",
+    "no-restricted-syntax": "off",
+    "no-shadow": "off",
+    "no-undef": "off",
+    "no-underscore-dangle": "off",
+    "no-unused-vars": "off",
+    "no-use-before-define": "off",
+    "object-curly-spacing": "off",
+    "one-var": "off",
+    "padded-blocks": "off",
+    "quote-props": "off",
+    "quotes": "off",
+    "semi": "off",
+    "space-before-function-paren": "off",
+    "space-unary-ops": "off",
+    "spaced-comment": "off",
+    "vars-on-top": "off",
+  }
+}

.travis.yml

@@ -6,11 +6,19 @@ env:
  - TOX_ENV=py27
  - TOX_ENV=docs
  - TOX_ENV=lint
+ - TOX_ENV=eslint
 cache:
   directories:
     - ~/.cache/pip
+    - ~/.nvm/nvm.sh
 install:
  - pip install tox
+ - curl -o- https://raw.githubusercontent.com/creationix/nvm/v0.33.2/install.sh | bash
+ - source ~/.nvm/nvm.sh
+ - nvm install --lts
+ - nvm use --lts
+ - npm install
+ - bower install
 script:
  - tox -e $TOX_ENV
 notifications:

gulpfile.js

@@ -12,6 +12,7 @@ var gulp = require('gulp'),
     vinyl_buffer = require('vinyl-buffer'),
     es = require('event-stream'),
     path = require('path'),
+    eslint = require('gulp-eslint'),
     pkg_config = require('./package.json');
 
 // Applications with primary static sources. We define these here to avoid
@@ -254,4 +255,15 @@ gulp.task('dev', function (done) {
         }));
 });
 
+gulp.task('lint', function (done) {
+    var paths = Object.keys(sources).map(function(application) {
+      return path.join(pkg_config.name, application, 'static-src', '**', '*.js');
+    });
+    return gulp
+        .src(paths)
+        .pipe(eslint())
+        .pipe(eslint.format())
+        .pipe(eslint.failAfterError());
+});
+
 gulp.task('default', ['build']);

package.json

@@ -11,8 +11,11 @@
     "bower-resolve": "^2.2.1",
     "browserify": "*",
     "debowerify": "git+https://github.com/agjohnson/debowerify.git#8c6b9a7",
+    "eslint-config-airbnb-base": "^11.2.0",
+    "eslint-plugin-import": "^2.2.0",
     "event-stream": "^3.3.1",
     "gulp": "*",
+    "gulp-eslint": "^3.0.1",
     "gulp-less": "^3.0.3",
     "gulp-rename": "^1.2.2",
     "gulp-run": "^1.6.6",

tox.ini

@@ -30,6 +30,9 @@ commands =
     --profile=prospector \
     --die-on-tool-error
 
+[testenv:eslint]
+commands =
+    gulp lint
 
 [testenv:coverage]
 deps =