lint-trap

This module contains standardized linting rules to be used across all projects at Uber that contain JavaScript.

Usage

npm install --save-dev lint-trap
./node_modules/.bin/lint-trap <list of file or folder paths>

It is recommended that you add lint-trap to the scripts property of your project's package.json manifest file, like so:

"scripts": {
    "lint": "lint-trap",
}

... and then you can invoke it by executing npm run lint.

Tips and Tricks for Legacy Projects

Using lint-trap to get a legacy project with many thousands of lines of code in line with the standards enforced by lint-trap can be a daunting task. To make the process as painless as possible, this guide will give you practical advice on tackling all your lint errors and warnings in bite-size chunks.

Linting Support in Text Editors

lint-trap is very new so support for text editor plugin is still immature. Plugin support already exists for SublimeText 3. Plugin support for syntastic is currently being worked on. Plugin support for flycheck in emacs is planned.

For more information and workarounds if your editor is not yet supported, see the documentation on code editor support.

Attenuating Rules

Since lint-trap is meant to enforce good coding style and consistency across many projects from the same organization, you cannot turn rules off completely. However, when using lint-trap in legacy projects without any linter or with different linting rules, it is useful to be able to downgrade the warning severity from error to warning so you can pay down linting technical debt over several commits. Because of this, lint-trap supports adding a .lintrc file to your project.

For more information on configuring a .lintrc file or command-line options, see the configuration docs.

If you're using lint-trap in a legacy project, you should also check out the legacy project tips.

Indentation

lint-trap dynamically detects whether it should enforce a 2-space or 4-space softtab indent rule. It does this by inspecting a reference file to detect the indentation used in that reference file, and then enforces the detected indentation on all the files it is linting.

For more information, see the documentation on indentation

Warnings vs. Errors

Almost all lint-trap rules produce errors. If you see an error, you should fix it. However, a few rules, notably max-statements and complexity produce warnings. The reason these rules produce warnings is because their goal is to highlight code where there might be too much going on within a single block of code.

Long, complex code blocks are likely to be less readable and therefore less maintainable. When you see a warning, you should investigate the code in question and deliberately determine if the code should be refactored or if the code is okay as is. There exist cases where lint-trap will return a warning, but where the code is acceptable as is. For example, you might find that in some tests you have many assertions and you go beyond the maximum number of statements allowed. In this situation you might determine that many assertions are not only acceptable but necessary without reducing readability and comprehension. If you encounter code that should be considered acceptable, you can add an inline linter directive to tell lint-trap to ignore that code for that particular warning.

Since all the lint rules that produce warnings are currently handled by eslint all you need to do is add the following two lines around your code, where lint-rule-id is the string eslint uses to identify a particular rule such as max-statements:

/*eslint-disable lint-rule-id*/
/* the code producing the warning here */
/*eslint-enable lint-rule-id*/

Contributing

Contributions to lint-trap are welcome, but since lint-trap is effectively a module that encapsulates a set of opinions and throws errors and warnings at you when you violate those opinions, there is a lot of room to debate over what color to paint our bikeshed.

Before you begin filing an issue to argue why you think your color of paint is superior, it's worth knowing how the current set of rules were determined. Javascript enginerrs from several teams with different needs (both front-end engineers and back-end NodeJS engineers) were the first to go through all the rules, try them out and debate the merit of each. This group is consists of developers that collectively have seen tons of code and tons of bugs in production systems at scale that arose from poor choice of coding style and conventions.

The rules and the reasoning behind each should all be documented or will be over time. Before we bikeshed over a rule, please check the rules documentation. If a rule hasn't been documented or hasn't yet been documented adequately, open an issue asking for clarification and better documentation first. If a rule has been documented and you still disagree, there is one task you must perform before you are allowed to bikeshed. You must first read Clay Shirky's essay A Group is its Own Worst Enemy. At the end of the day, we all love bikeshedding, but we would like to keep it to a minimum, so we can all get work done.

Why lint-trap

If there are all these other linters out there like JSHint, ESLint and jscs, why does lint-trap exist?

Uber like many large companies using JavaScript has a LOT of projects all with their own set of .rc files (pronounced dot·arc) for each linter. These configuration files are almost always copypasta-ed from a a previous project and they all evolve and mutate over time as each developer gets their hands on a project and make their own changes. This means that over time, every project ends up with its own style adding unnecessary friction to collaboration and working across many projects.

lint-trap aims to be a zero-configuration linter as much as possible, and requires no configuration in brand new projects. The few configuration options it offers exist solely to help legacy projects reach 100% linting conformance piecemeal.

For more information on why we think lint-trap is valuable see the documentation describing the philosopy behind lint-trap

Using lint-trap in non-Uber projects

lint-trap currently includes hard-coded lint rules in use at Uber. If you work at Uber and work with JavaScript, you should have lint-trap in your project. If you don't work at Uber, you're welcome to use lint-trap in your project as is.

If you want lint-trap to support a different rules for your organization, we first ask that you try out the rules with which lint-trap already comes. The rules have been discussed at length by many engineers and are well thought out for any environment where lots of devs need to work together and need to feel at home in each others' code. Spend some time with the existing rules and reading the explanation for their existance in the docs and we're pretty sure you'll find them to be a pretty good balance for large engineering organizations.

If, after trying out our lint-rules for some time, you feel that you still need to support different rules, please comment on this issue. We will be glad to work with you to add support for this lint-trap.

License

The MIT License (MIT)

Copyright (c) 2014 Uber Technologies, Inc.

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.