Code Style Article

[will]

I’m thinking eslint shouldn’t give errors when following the guide, eg after creating a new default app. Or to be more precise – I was expecting it not to give errors, and it did.

Eg running:

meteor create myapp
meteor npm install
meteor npm install --save-dev eslint eslint-plugin-react eslint-plugin-meteor eslint-config-airbnb

and populating scripts and eslintConfig as above in package.json, then "meteor npm run lint" gave me:

> myapp@ lint /opt/www/sites/me/myapp
> eslint .


/opt/www/sites/me/myapp/client/main.js
   1:26  error  Unable to resolve path to module 'meteor/templating'    import/no-unresolved
   2:29  error  Unable to resolve path to module 'meteor/reactive-var'  import/no-unresolved
  18:25  error  Invalid parameter name, use "templateInstance" instead  meteor/eventmap-params

/opt/www/sites/me/myapp/server/main.js
  1:24  error  Unable to resolve path to module 'meteor/meteor'  import/no-unresolved

✖ 4 problems (4 errors, 0 warnings)

I eventually made it quiet with rules in package.json:

"rules": {
  "meteor/eventmap-params": [
    2, { "templateInstanceParamName": "instance" }
  ],
  "import/no-unresolved": [
    2, { "ignore": ["^meteor/"] }
  ]
}

Should that be included or noted?

[sashko]

Yeah we should definitely either fix this or mention it in the guide. If you have a moment, please submit a PR to add your config to the guide!

[suhaila]

This type of import works in Meteor

import xxx from ‘/client/xxx’

but it is shown as import/no-unresolved when linting. This can be solved using ignore rule in eslintrc. Is there any other way to satisfy this rule instead of ignoring it.

[sashko]

@suhaila yeah check the bottom of this section, it tells you how to ignore only meteor/*: http://guide.meteor.com/code-style.html#eslint-installing

[trajano]

Perhaps we can add something about meteor lint and use something like https://atmospherejs.com/dburles/eslint to perform the linting for us. I say “something like” as I get Error: No os unibuild for null! when using eslint as noted by https://github.com/meteor/meteor/issues/6843#issuecomment-215804381

[trajano]

I eventually made it quiet with rules in package.json:

Instead of defining the ignores yourself I recommend adding https://github.com/clayne11/eslint-import-resolver-meteor this will reduce your rules to {}

Here’s the relevant PR https://github.com/meteor/guide/pull/434 perhaps someone can take the time to update the todo app?

However if you need an example of this, I have it on https://github.com/trajano/meteor-boilerplate/blob/meteor-skeleton-1.0.3/.eslintrc.json

The angular branch of my boilerplate has an unstyled todo app written in AngularJS1 since angular1 doesn’t seem to get enough love here

[rdagger]

The editor integration section for linter-eslint seems to be missing a step for the Atom integration (at least with respect to React). It doesn’t like the tags in your render() code:

Parsing error: Unexpected token

[ArturoMaltos]

This is what I did to make it work with vim, meteor and lint.

Get all the npm packages, in my case I need to use the same packages for vim, so I installed them globally.

sudo npm install -g --save-dev eslint-config-airbnb eslint-plugin-import eslint-plugin-meteor eslint-plugin-react eslint-plugin-jsx-a11y eslint

Edit the packages.json with the lint shortcut.

{
    ....
    "scripts": {
      "start": "meteor run",
      "lint": "eslint .",
      "pretest": "npm run lint --silent"
    },
    ...
}

Create the .eslintrc with this settings.

{
	"plugins": [
	    "meteor"
	],
	"extends": [
	    "airbnb",
	    "plugin:meteor/recommended"
	],
	"rules": {
	    "meteor/eventmap-params": [
	        2, { "templateInstanceParamName": "instance" }
	    ],
	    "import/no-unresolved": [
	        2, { "ignore": ["^meteor/"] }
	    ],
	    // enable this._variable (used many times to refer the this._id)
	    "no-underscore-dangle": ["error", { "allowAfterThis": true }],
	    // my indentation is four spaces (sorry, its better for me)
	    "indent": ["error", 4],
	    // meteor uses globals and includes a lot
	    "no-unused-vars": 0,
            // enable console
            "no-console": 0,
	},
	"env": {
	    "meteor": true,
	    "node": true,
	    "browser": true
	},
	// ignore some undeclared global variables and methods
	// used by Meteor
	"globals": {
	    "describe": false,
	    "it": false,
	    "before": false,
	    "beforeEach": false,
	    "after": false,
	    "afterEach": false
	}
}

Install the scrooloose/syntastic Vundle in Vim.

" Lint
Plugin 'scrooloose/syntastic'
let g:syntastic_javascript_checkers = ['eslint']
let g:syntastic_check_on_open=1

Now meteor and vim are using the same .eslinrc configuration file. I can lint with Meteor and also get the lint error report from vim.

[trajano]

“lint”: “eslint .”,

How do you prevent it from scanning .meteor, node_modules and packages?

[rdagger]

I think the guide should include a little more details of how incredibly helpful ESLint can be for React. It provides much more than style and typo checking. I’ve found it very helpful to improving my React programming. For example: warning a component should be a pure render function instead of a class and when function binding can cause inefficient garbage collection.

A few other notes:

1. In Windows, you should install the NPM plugins globally. Otherwise, you can double your build times.
2. In Atom, I only had to install ESLint. It automatically installed the dependencies and I don’t think Babel is necessary.
3. In Atom, you need to set the ESLint global installation flag if the you install the NPM plugins globally.
4. For react, you need to set up parser options in your eslintrc.json file for ecmaVersion and sourceType.

[trajano]

In Windows, you should install the NPM plugins globally. Otherwise, you can double your build times.

Is there any evidence or reason to this? Or are you talking specifically about meteor build?

[rdagger]

After I installed the ESLint plugins locally, Meteor went from 16 to 40 seconds to restart any time I saved changes. Switching to global lowered my build times back to 16 seconds. This is only on Windows. On Ubuntu, the local install had no effect.
Here’s a thread I posted discussing it.

[msio]

in Code style doc you are writing

Collections should be named as a plural noun, in PascalCase. The name of the collection in the database (the first argument to the collection constructor) should be the same as the name of the JavaScript symbol.

but users collection is in db lowercase, how can I change it ?
Thanks
Best Regards

[rlivingston]

Instead of defining the ignores yourself I recommend adding https://github.com/clayne11/eslint-import-resolver-meteor this will reduce your rules to {}

I just want to second this piece of advice and thank @trajano for it! This is the key to getting the false positive errors on absolute paths to go away.

I’ve seen many posts where people are indicating that absolute paths in import statements weren’t working. They work. They are interpreted by Meteor as paths relative to the project root directory. But without this resolver, ESLint is telling everyone that they are errors, and people are confusing that with Meteor not supporting it. I dug into Meteor’s module code and found that not only are the absolute paths supported, but the very first test verifies that they work. This is explicit support.

To expand on the installation of this, it is an NPM module. So add it to the “npm install” command recommended in the article as follows…

meteor npm install --save-dev eslint-config-airbnb eslint-plugin-import eslint-import-resolver-meteor eslint-plugin-meteor eslint-plugin-react eslint-plugin-jsx-a11y eslint

Of course, if you already have the others just…

meteor npm install --save-dev eslint-import-resolver-meteor

Then add the following to your .eslintrc.json file

  "settings": {
    "import/resolver": "meteor"
  },

[sashko]

Can someone send a PR to add this stuff to the guide article?

[rlivingston]

Your wish is my command (today)! Done.

[rlivingston]

With the advent of conditional and nested import support in Meteor 1.3.3 and up, ESLint “breaks” if you make use of a conditional or nested import within a module.

To expand on that, if you use code like

if (this.isServer) {
   import { ServerSauce } from './server/serverOnlyCode';
}

ESLint will give a syntax error similar to the following and stop processing the file.

272:7  error  Parsing error: 'import' and 'export' may only appear at the top level

Luckily, the maintainers of babel-eslint, an alternative parser for ESLint, accepted a PR to implement an option that allows this syntax.

To get ESLint to work with nested imports and exports (yes, have not yet seen a use-case for them but conditional exports work too with Ben’s changes), just run

$meteor npm install --save-dev babel-eslint

to get the latest version of babel-eslint (>= 6.1.0) and add the following into your ESLint configuration in package.json or .eslintrc.json:

  "parser": "babel-eslint",
  "parserOptions": {
    "allowImportExportEverywhere": true
  },

I’ll create a guide PR to show this there too.

[trajano]

You can use

const ServerSauce = require('./server/serverOnlyCode').ServerSauce

Without having to update eslint.

As for a use case for conditional loads, I use it as part of my gulpfile.js to prevent the actual gulp file from being loaded in Meteor

if (typeof Meteor === typeof undefined) {
  // eslint-disable-next-line vars-on-top, no-var
  var r = require
  r('./.gulp/gulpfile')
}

[rlivingston]

Of course, require can still be used, but the point of the new support is to get rid of the split personality aspect of using two different module systems in one file. Since Ben implemented it as an NPM module, reify, a means is now available to the whole NPM community to stop using require throughout their file, not just at the top level.

My comment on the use-case was concerning conditional exports, not imports. I believe they were included mostly to maintain import <> export symmetry. I haven’t yet dug into experimenting with conditional exports other than to verify that something with a conditional export does in fact build.

[dbx834]

+1 for JSDoc recommendation.

You could even enforce it with ESLint like so,

in eslintConfig

...
"valid-jsdoc": "error",
  "require-jsdoc": [
    "error",
    {
      "require": {
        "FunctionDeclaration": true,
        "MethodDefinition": true,
        "ClassDeclaration": true
      }
    }
  ],
...

I don’t think though enforcing JSDoc would make for a nice experience for those who are just starting out with Meteor. ‘Gentle suggestions’ for beginners and ‘Highly recommended’ for large projects with multiple devs.