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For ESLint’s entire 11 year existence, we’ve only maintained one major release line at a time. This was both for practical reasons (limited team bandwidth) and technical reasons (our infrastructure was built to assume just one branch). Unfortunately, we haven’t been good at communicating our version support policy, which has led to confusion and frustration when we do a major release. Adopting a f

Highlights Types now included We’ve been receiving complaints about the @types/eslint package not being updated after the v9 release. While we did do an initial update to the package for v9, it quickly became apparent that regular updates to that package could not be accomplished in a timely manner. Ultimately, we decided that the only way for us to provide the type of experience we want for ESLin

Version Support The ESLint team provides ongoing support for the current version and six months of limited support for the previous version. Major ESLint release lines move through a status of Current, to Maintenance, to End of Life (EOL). A release line is considered Current when prerelease work begins. At that point, the previous release line moves to Maintenance status and stays there until six

Highlights Here are some of the key changes in this release. Experimental TypeScript configuration files Arya Emami landed experimental support for TypeScript configuration files. Specifically, you can now use eslint.config.ts, eslint.config.mts, and eslint.config.cts files as your configuration files. Because this feature is experimental, you’ll need to use the unstable_ts_config feature flag: np

When we released ESLint v9.0.0 in April, it was the first major release in 30 months and formally introduced the new configuration system. ESLint v9.0.0 also made some rule API changes to prepare the core for what’s coming next. After the release, we spent a lot of time creating compatibility utilities, a configuration migration tool, and a rule API transform utility to help the ecosystem move to

We’ve heard you: One of the biggest reasons ESLint users haven’t upgraded to ESLint v9.x is migrating a configuration file seems difficult and complicated. Some plugins support flat config and the ESLint v9.x rule APIs and some don’t. Sometimes you need to use FlatCompat and sometimes you need to use the compatibility utilities. While we cover as much as we can in the migration guide, it can take

The release of ESLint v9.0.0 brought with it the rollout of the new configuration system, but also a series of changes to the rules API. These changes are necessary in order to prepare ESLint for implementing language plugins, which will give ESLint the ability to natively lint languages other than JavaScript. As a result, plugin authors needed to update their rules to work with v9.0.0, and unfort

As of ESLint v9,0.0, the new configuration system has reached general availability, bringing with it many benefits. Configuration files are now easier to manage and more transparent to compose. However, it can still be non-trivial to understand which rules are enabled and disabled for specific files, especially when your configuration is complex or composed from multiple sources. That’s why we are

Highlights This is a summary of the significant changes, both breaking and non-breaking, you need to know about when upgrading from ESLint v8.x to ESLint v9.0.0. Installing Because this is a major release, you may not automatically be upgraded by npm. To ensure you are using this version, run: npm i eslint@9.0.0 --save-dev Migration Guide As there are a lot of changes, we’ve created a migration gu

Highlights This release backports from v9.x to v8.x two new features and several bug fixes related to the flat config system to help plugins, integrations and users migrate to flat config ahead of the final v9.0.0 release. Support for eslint.config.mjs and eslint.config.cjs This release introduces support for eslint.config.mjs and eslint.config.cjs configuration files to v8.x in addition to eslint

To address: If you are using any of these formatters via the -f command line flag, you’ll need to install the respective package for the formatter. Related issue(s): #17524 Removed require-jsdoc and valid-jsdoc rules The require-jsdoc and valid-jsdoc rules have been removed in ESLint v9.0.0. These rules were initially deprecated in 2018. To address: Use the replacement rules in eslint-plugin-jsdoc

Last month, the Technical Steering Committee (TSC) met to finalize the features for ESLint v9.0.0. This post outlines our plans for v9.0.0. You can keep up to date everything that is planned for v9.0.0 on our project board. Development plan Due to the large number of breaking changes planned for v9.0.0, we have decided to develop this release in two phases: Alpha. The alpha release will be compris

In ESLint v8.53.0, scheduled to be released on Friday, November 3, 2023, we will formally deprecate our formatting rules. Formatting rules are those rules that simply enforce code conventions around spacing, semicolons, string formats, etc. For a variety of reasons, which are discussed in this post, this is the right decision for ESLint going forward. However, to understand how we got here, it’s h

It may seem hard to believe, but the RFC for ESLint’s new configuration system, nicknamed flat config, was first written in 2019. It took until 2022 (v8.21.0) for us to release an experimental, opt-in version of flat config. Since then, we’ve been making changes and improvements based on feedback from the community. The plan was always to allow the current configuration system, nicknamed eslintrc,

When ESLint v9.0.0 is released, it will ship with several breaking changes for rule authors. These changes are necessary as part of the work to implement language plugins, which gives ESLint first-class support for linting languages other than JavaScript. We’ve had to make these changes because ESLint has, from the start, assumed that it would only ever be used to lint JavaScript. As such, there w

In our 2022 year in review, we briefly mentioned a couple of project kickoffs, and we’re excited to now announce the official eslint-community GitHub organization. The strength of ESLint is in its ecosystem, and we continue to investigate different ways of further supporting that community. We began by donating to community projects, to ensure that high-value projects were receiving the funds they

In February 2022, we shared our plan for 2022, including how the ESLint project as a whole would be spending its sponsorship money for the betterment of the project. In this post, I’ll share what we achieved during the year. Website redesign The most recognizable change to the project was undoubtedly the website redesign. The new website was officially launched on June 23 and was immediately met w

Highlights Formatters now have access to the --max-warnings threshold when it is exceeded. See Working with Custom Formatters - The context Argument for details. The new config system no longer supports .eslintignore files, --ignore-path CLI option and ignorePath API option, due to observed incompatibilities with ignores in eslint.config.js configuration files. For ignoring files in the new config

Highlights The new config system is now incorporated into the CLI, along with the existing config system. To opt-in to the new config system, place a eslint.config.js file in the root of your project. Please note that this is still an experimental feature and we welcome your feedback! The no-fallthrough rule has a new option allowEmptyCase. The no-warning-comments rule has a new option decoration.

In my previous post, I talked about how the eslintrc config system had grown to be more complex than necessary through a series of small, incremental changes. The flat config system, on the other hand, was designed from the start to be simpler in a number of ways. We took all of the learnings from the previous six years of ESLint development to come up with a holistic approach to configuration tha

When ESLint was first released in 2013, the config system was fairly simple. You could define the rules you wanted to enable or disable in a .eslintrc file. When a file was linted, ESLint would first look in the same directory as that file for a .eslintrc file and then continue up the directory hierarchy until reaching the root, merging configurations from all the .eslintrc files found along the w

In ESLint v8.14.0 I contributed a new core rule called no-constant-binary-expression which has surprised me with the wide variety of subtle and interesting bugs it has been able to detect. In this post I’ll explain what the rule does and share some examples of real bugs it has detected in popular open source projects such as Material UI, Webpack, VS Code, and Firefox as well as a few interesting b

Published 09 Oct, 2021 under Release Notes ESLint v8.0.0 released We just pushed ESLint v8.0.0, which is a major release upgrade of ESLint. This release adds some new features and fixes several bugs found in the previous release. This release also has some breaking changes, so please read the following closely. Highlights There are several breaking changes in v8.0.0. We’ve created a migration guid

Published 24 Sep, 2021 under Release Notes ESLint v8.0.0-rc.0 released We just pushed ESLint v8.0.0-rc.0, which is a new prerelease version for ESLint v8. This release adds some new features and fixes several bugs found in the previous release. Highlights This is a summary of the major changes you need to know about for this version of ESLint. This version of ESLint is provided to gather feedback