WRITING CUSTOM ESLINT RULES

We need to do two things: You can do that with the following NPM command: Make sure your tests pass! That becomes a problem both for new hires, which have to take more time to ramp up, and for current dev switching jobs as they’ll have a hard time abandoning what they learned. Use YeoMan and the corresponding EsLint generator Create your own package The generator sets you up with a nice folder structure, including tests, a proper description and some documentation. In a custom rule or plugin, you can omit docs or include any properties that you need in it. Tools help you get the job done, not get in the way.

The third and often overlooked set of testing is continuity testing, also known as static code analysis. The yeoman rule generator will give us a few new files:. Ideally, we want the following:. Each bundled rule for ESLint core must have a set of unit tests submitted with it to be accepted. Unfortunately, the ESLint autofix infrastructure is not as mature as the rule infrastructure. ESLint is a powerful linting utility for Javascript and is highly configurable and extendable.

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writing custom eslint rules

As I mentioned before, if you want to share your plugin, you can distribute it via NPM. As soon as we notice no more warnings for one of these rules, we will switch them to errors.

writing custom eslint rules

If you make a fix function which edlint multiple fixing objects, those fixing objects must not be overlapped. Engineers at Flexport are opinionated about the code we write.

Creating custom rules for ESLint

From here you should create a test to try out possible valid and invalid code snippets to make sure that everything is still valid. It matches the method signature sounds. These methods return an array of comments that appear directly before, directly after, and inside nodes, respectively. Afterwards, any remaining problems will be reported as usual. Rule bundled rule for ESLint core must have a set of unit tests submitted with it to be accepted. Your engineering team has a strong preference about how to set something up, but others might choose a different option.

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Working with Rules – ESLint – Pluggable JavaScript linter

The documentation mentions a way to write custom rules in a local directory and running them through a command-line option. Finally, just npm install and you have yourself a plugin! But in some cases, you might want to enforce one or more ESLint code rules that are specific to your particular project.

Unfortunately, the ESLint autofix infrastructure is not as mature as the rule infrastructure. ESLint provides the RuleTester utility to make it easy to write tests for rules. There are plenty of possibilities for custom EsLint rules and most of it depends on your project. You should use a SourceCode object whenever you need to get more information about the code being linted. Analyzing code Asbtract Syntax Trees Before we start writing custom EsLint rules, I first want to show how code is analyzed and how we can plug in to that.

It also prevents errors reported in different sections of your rule from having out-of-date messages. ESLint is a great tool when it comes to code standardization.

writing custom eslint rules

These options appear in configuration. This process will repeat up to 10 times, or until no more fixable problems are found. Earlier versions of ESLint supported additional methods on the context object.

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Writing custom ESLint rules for your picky developers | Hacker News

If you are using ESLint as part of your continuous integration pipeline, you may not writijg able to simply enable your new rule as it would break the build. Fill in your details below or click an icon to log in: The simplest example is to use just node and message:.

In those cases, you can just create the folder with your plugin locally and commit it to your code repository. In statically compiled languages, we usually lean on the compiler to catch out common errors or plain stupidities. The next example shows some sample code and the corresponding syntax tree: Eslknt continuing to use this website, you agree to their use.

First we need to know what part of the static tree we are going to lint.

Writing custom EsLint rules

Were going to setup a new project from scratch. Custom EsLint rules come in handy on a project-level basis. If you submit a core rule to the ESLint repository, you must follow some conventions explained below.

In the example below it is called.