GitHub user 1ambda opened a pull request:
https://github.com/apache/zeppelin/pull/1887
[ZEPPELIN-1940] most of eslint rules are NOT applied at all
### What is this PR for?
**Most fixes are about applying lint rules. It's automatically fixed using
`eslint --fix` command.**
**So please review `Gruntfile.js`, `.eslint`, `package.json` in
`zeppelin-web` directory**
As a result of the PR,
- Restored javascript lint system
- Fixed 1500+ lint errors
- Found some buggy code (e.g `Unexpected 'this' no-invalid-this` See the
screenshot section)
We are using google style guide but it is not used at all because of
invalid `.eslint` configuration. Thus I made some changes to fix it.
- Moved eslint from grunt to webpack (faster)
- Changed invalid config `"preset": "google"` to `"extends": ["google"]`
- Fixed 1500+ lint errors automatically using `eslint --fix` command
- Left some lint errors i cannot fix immediately as warnings or disabled
```
"guard-for-in": [1], // warning
"no-invalid-this": [1], // warning
"prefer-rest-params": [1], // warning
"require-jsdoc": [0], // disabled
"valid-jsdoc": [0] // disabled
```
- Also, Modified 20+ lint errors by hand
```
@ ./src/index.js 29:0-65
ERROR in ./src/app/visualization/builtins/visualization-areachart.js
Module build failed: Duplicate declaration "self"
73 | this.chart.style(this.config.style || 'stack');
74 |
> 75 | let self = this;
| ^
/Users/lambda/github/apache-zeppelin/zeppelin-master/zeppelin-web/src/app/visualization/visualization.js
134:14 error Unexpected var, use let or const instead no-var
138:14 error Unexpected var, use let or const instead no-var
...
```
- Additionally, introduced `eslint:recommended` ruleset for several rules
which google style is not opinionated so that we can keep clear, unified rules.
### What type of PR is it?
[Bug Fix | Improvement]
### Todos
* [x] - Moved eslint (build) task from grunt to npm (package.json)
* [x] - Brought eslint (dev) task from grunt to webpack
* [x] - Fixed `.eslint` to applied google ruleset
* [x] - Modifed some lint errors while leaving others as warning which i
cannot fix right now (e.g docs)
* [x] - Introduced eslint recommended ruleset
### What is the Jira issue?
[ZEPPELIN-1940](https://issues.apache.org/jira/browse/ZEPPELIN-1940)
### How should this be tested?
- execute `npm run dev` and `npm run build` to check whether lint works well
### Screenshots (if appropriate)
### Image: found some invalid code using restored lint
### Image: found some errors using restored lint
### Image: Some code fixed by hand
```
â zeppelin-web git:(remove-grunt-eslint) npm run lint:js -- --quiet
> zeppelin-web@0.0.0 lint:js
/Users/lambda/github/apache-zeppelin/zeppelin-master/zeppelin-web
> eslint src test Gruntfile.js "--quiet"
/Users/lambda/github/apache-zeppelin/zeppelin-master/zeppelin-web/src/app/handsontable/handsonHelper.js
159:58 error Use the rest parameters instead of 'arguments'
prefer-rest-params
163:55 error Use the rest parameters instead of 'arguments'
prefer-rest-params
/Users/lambda/github/apache-zeppelin/zeppelin-master/zeppelin-web/src/app/notebook/notebook.controller.js
635:20 error Unexpected var, use let or const instead no-var
648:20 error Unexpected var, use let or const instead no-var
/Users/lambda/github/apache-zeppelin/zeppelin-master/zeppelin-web/src/app/notebook/paragraph/paragraph.controller.js
929:28 error Use the rest parameters instead of 'arguments'
prefer-rest-params
930:66 error Use the rest parameters instead of 'arguments'
prefer-rest-params
/Users/lambda/github/apache-zeppelin/zeppelin-master/zeppelin-web/src/app/notebook/paragraph/result/result.controller.js
386:9 error Unexpected var, use let or const insteadno-var
433:9 error Unexpected var, use let or const insteadno-var
453:9 error Unexpected var, use let or const insteadno-var
867:28 error Use the rest parameters instead of 'arguments'
prefer-rest-params
868:66 error Use the rest parameters instead of 'arguments'
prefer-rest-params
/Users/lambda/github/apache-zeppelin/zeppelin-master/zeppelin-web/src/app/tabledata/transformation.js
52:7 error Unexpected var, use let
