+ + See v6--typescript-eslint.netlify.app for documentation on upcoming v6 release. + +
+👆
diff --git a/packages/website/blog/2023-03-13-announcing-typescript-eslint-v6-beta.md b/packages/website/blog/2023-03-13-announcing-typescript-eslint-v6-beta.md new file mode 100644 index 000000000000..feb68f087dfc --- /dev/null +++ b/packages/website/blog/2023-03-13-announcing-typescript-eslint-v6-beta.md @@ -0,0 +1,309 @@ +--- +authors: + - image_url: https://www.joshuakgoldberg.com/img/josh.jpg + name: Josh Goldberg + title: typescript-eslint Maintainer + url: https://github.com/JoshuaKGoldberg +description: Describing what an AST (Abstract Syntax Tree) is and why it's useful for ESLint and TypeScript tooling. +slug: announcing-typescript-eslint-v6-beta +tags: [breaking changes, typescript-eslint, v5, v6] +title: Announcing typescript-eslint v6 Beta +--- + +[typescript-eslint](https://typescript-eslint.io) is the tooling that enables standard JavaScript tools such as [ESLint](https://eslint.org) and [Prettier](https://prettier.io) to support TypeScript code. +We've been working on a set of breaking changes and general features that we're excited to get in front of users soon. +And now, after over two years of development, we're excited to say that typescript-eslint v6 is ready for public beta testing! 🎉 + +Our plan for typescript-eslint v6 is to: + +1. Have users try out betas starting in early March of 2023 +2. Respond to user feedback for the next 1-3 months +3. Release a stable version summer of 2023 + +Nothing mentioned in this blog post is set in stone. +If you feel passionately about any of the choices we've made here -positively or negatively- then do let us know on [the typescript-eslint Discord's `v6` channel](https://discord.com/channels/1026804805894672454/1084245444676292688)! + +## Trying Out v6 + +Please do try out the typescript-eslint v6 beta! +Its documentation site is hosted on a preview deploy link: **[v6--typescript-eslint.netlify.app](https://v6--typescript-eslint.netlify.app)**. + +### As A New User + +If you don't yet use typescript-eslint, you can go through our [configuration steps on the v6 _Getting Started_ docs](https://v6--typescript-eslint.netlify.app/getting-started). +It'll walk you through setting up typescript-eslint in a project. + +### As An Existing User + +If you already use typescript-eslint, you'll need to first replace your package's previous versions of `@typescript-eslint/eslint-plugin` and `@typescript-eslint/parser` with `@rc-v6` versions: + +```shell +npm i @typescript-eslint/eslint-plugin@rc-v6 @typescript-eslint/parser@rc-v6 --save-dev +``` + +We highly recommend then basing your ESLint configuration on the reworked typescript-eslint [recommended configurations mentioned later in this post](#configuration-breaking-changes) — especially if it's been a while since you've reworked your linter config. + +## User-Facing Breaking Changes + +These are the changes that users of typescript-eslint -generally, any developer running ESLint on TypeScript code- should pay attention to when upgrading typescript-eslint from v5 to v6. + +> ⏳ indicates a change that has been scheduled for v6 but not yet released. +> We'll update this blog post as the corresponding pull requests land. + +### Reworked Configuration Names + +The biggest configuration change in typescript-eslint v6 is that we've reworked the names of our [provided user configuration files](https://typescript-eslint.io/linting/configs). +typescript-eslint v5 provided three recommended configurations: + +- [`plugin:@typescript-eslint/recommended`](https://typescript-eslint.io/linting/configs#recommended): Recommended rules for code correctness that you can drop in without additional configuration. +- [`plugin:@typescript-eslint/recommended-requiring-type-checking`](https://typescript-eslint.io/linting/configs#recommended-requiring-type-checking): Additional recommended rules that require type information. +- [`plugin:@typescript-eslint/strict`](https://typescript-eslint.io/linting/configs#strict): Additional strict rules that can also catch bugs but are more opinionated than recommended rules. + +Those configurations worked well for most projects. +However, some users correctly noted two flaws in that approach: + +- Strict rules that didn't require type checking were lumped in with those that did. +- _Stylistic_ best practices were lumped in with rules that actually find bugs. + +As a result, we've reworked the configurations provided by typescript-eslint into these two groups: + +- Functional rule configurations, for best best practices and code correctness: + - **`plugin:@typescript-eslint/recommended`**: Recommended rules that you can drop in without additional configuration. + - **`plugin:@typescript-eslint/recommended-type-checked`**: Additional recommended rules that require type information. + - **`plugin:@typescript-eslint/strict`**: Additional strict rules that can also catch bugs but are more opinionated than recommended rules _(without type information)_. + - **`plugin:@typescript-eslint/strict-type-checked`**: Additional strict rules that do require type information. +- Stylistic rule configurations, for consistent and predictable syntax usage: + - **`plugin:@typescript-eslint/stylistic`**: Stylistic rules you can drop in without additional configuration. + - **`plugin:@typescript-eslint/stylistic-type-checked`**: Additional stylistic rules that require type information. + +> `plugin:@typescript-eslint/recommended-requiring-type-checking` is now an alias for `plugin:@typescript-eslint/recommended-type-checked`. +> The alias will be removed in a future major version. + +As of v6, we recommend that projects enable two configs from the above: + +- If you are _not_ using typed linting, enable `stylistic` and either `recommended` or `strict`, depending on how intensely you'd like your lint rules to scrutinize your code. +- If you _are_ using typed linting, enable `stylistic-type-checked` and either `recommended-type-checked` or `strict-type-checked`, depending on how intensely you'd like your lint rules to scrutinize your code. + +For example, a typical project that enables typed linting might have an ESLint configuration file like: + +```js title=".eslintrc.cjs" +module.exports = { + extends: [ + 'eslint:recommended', + 'plugin:@typescript-eslint/recommended-type-checked', + 'plugin:@typescript-eslint/stylistic-type-checked', + ], + plugins: ['@typescript-eslint'], + parser: '@typescript-eslint/parser', + parserOptions: { + project: true, + tsconfigRootDir: __dirname, + }, + root: true, +}; +``` + +See [_Configurations_ on the v6 docs site preview](https://v6--typescript-eslint.netlify.app/linting/configs) for the updated documentation on configurations provided by typescript-eslint. + +For more information on these changes, see: + +- [Configs: Have recommended/strict configs include lesser configs, and simplify type checked names](https://github.com/typescript-eslint/typescript-eslint/discussions/6019) for the discussion leading up to these configuration changes. +- [feat(eslint-plugin): rework configs: recommended, strict, stylistic; -type-checked](https://github.com/typescript-eslint/typescript-eslint/pull/5251) for the pull request implementing the changes. + +### Updated Configuration Rules + +Every new major version of typescript-eslint comes with changes to which rules are enabled in the preset configurations - and with which options. +Because this release also includes a reworking of the configurations themselves, the list of changes is too large to put in this blog post. +Instead see the table in [Changes to configurations for 6.0.0](https://github.com/typescript-eslint/typescript-eslint/discussions/6014) for a full list of the changes. + +Please do try out the new rule configurations presets and let us know in that discussion! + +:::tip +If your ESLint configuration contains many `rules` configurations, we suggest the following strategy to start anew: + +1. Remove all your rules configurations +2. Extend from the preset configs that make sense for you +3. Run ESLint on your project +4. In your ESLint configuration, turn off any rules creating errors that don't make sense for your project - with comments explaining why +5. In your ESLint configuration and/or with inline `eslint-disable` comments, turn off any rules creating too many errors for you to fix - with _"TODO"_ comments linking to tracking issues/tickets to re-enable them + +::: + +Miscellaneous changes to all shared configurations include: + +- [fix(eslint-plugin): remove valid-typeof disable in eslint-recommended](https://github.com/typescript-eslint/typescript-eslint/pull/5381): Removes the disabling of ESLint's `valid-typeof` rule from our preset configs. + +### Rule Breaking Changes + +Several rules were changed in significant enough ways to be considered breaking changes: + +- Previously deprecated rules are deleted ([chore(eslint-plugin): remove deprecated rules for v6](https://github.com/typescript-eslint/typescript-eslint/pull/6112)): + - `@typescript-eslint/no-duplicate-imports` + - `@typescript-eslint/no-implicit-any-catch` + - `@typescript-eslint/no-parameter-properties` + - `@typescript-eslint/sort-type-union-intersection-members` +- [feat(eslint-plugin): [prefer-nullish-coalescing]: add support for assignment expressions](https://github.com/typescript-eslint/typescript-eslint/pull/5234): Enhances the [`@typescript-eslint/prefer-nullish-coalescing`](https://typescript-eslint.io/prefer-nullish-coalescing) rule to also check `||=` expressions. +- [fix(eslint-plugin): [prefer-function-type] check for merges with type checking](https://github.com/typescript-eslint/typescript-eslint/pull/6104): Fixes edge case bugs in the [`@typescript-eslint/prefer-function-type`](https://typescript-eslint.io/prefer-function-type) rule around function type merges, at the cost of making it require type information. +- ⏳ [feat(eslint-plugin): [prefer-optional-chain] use type checking for strict falsiness](https://github.com/typescript-eslint/typescript-eslint/pull/6240): Fixes edge case bugs in the [`@typescript-eslint/prefer-optional-chain`](https://typescript-eslint.io/prefer-optional-chain) rule around false positives, at the cost of making it require type information. + +### Tooling Breaking Changes + +- [feat(typescript-estree): deprecate createDefaultProgram](https://github.com/typescript-eslint/typescript-eslint/pull/5890): Renames `createDefaultProgram` to `deprecated__createDefaultProgram`, with associated `@deprecated` TSDoc tags and warnings. +- [feat: drop support for node v12](https://github.com/typescript-eslint/typescript-eslint/pull/5918) +- [feat: bump minimum supported TS version to 4.2.4](https://github.com/typescript-eslint/typescript-eslint/pull/5915): this matches [DefinitelyTyped's 2-year support window](https://github.com/DefinitelyTyped/DefinitelyTyped#support-window). +- [chore: drop support for ESLint v6](https://github.com/typescript-eslint/typescript-eslint/pull/5972) + +## Developer-Facing Changes + +typescript-eslint v6 comes with a suite of cleanups and improvements for developers as well. +If you author any ESLint plugins or other tools that interact with TypeScript syntax, then we recommend you try out typescript-eslint v6 soon. +It includes some breaking changes that you may need to accommodate for. + +:::tip +If you're having trouble working with the changes, please let us know on [the typescript-eslint Discord's `v6` channel](https://discord.com/channels/1026804805894672454/1084245444676292688)! +::: + +### Type Checker Wrapper APIs + +As described in our [ASTs and typescript-eslint](/blog/asts-and-typescript-eslint) post, ESLint rules don't natively work with AST nodes compatible with TypeScript's API. +Retrieving type information for an ESLint AST node in a custom rule requires code somewhat like: + +```ts title="custom-rule-with-v5.ts" +{ + // ... + create() { + const services = util.getParserServices(context); + const checker = services.program.getTypeChecker(); + const tsNode = services.esTreeNodeToTSNodeMap.get(esNode); + const type = checker.getTypeAtLocation(node); + + // ... + } + // ... +} +``` + +How cumbersome, just to call to a single method (`getTypeAtLocation`) on the TypeScript API! + +In typescript-eslint v6, we've added a set of wrapper APIs on the `services: ParserServices` object that act as shortcuts for commonly used TypeScript APIs including `getTypeAtLocation`: + +```ts title="custom-rule-with-v6.ts" +{ + // ... + create() { + const services = util.getParserServices(context); + const type = services.getTypeAtLocation(node); + + // ... + } + // ... +} +``` + +For now, the available wrapper APIs are: + +- `getSymbolAtLocation`: passes an ESTree's equivalent TypeScript node to `checker.getSymbolAtLocation` +- `getTypeAtLocation`: passes an ESTree node's equivalent TypeScript node to `checker.getTypeAtLocation` + +We hope these wrapper APIs make it more convenient to write lint rules that rely on the awesome power of TypeScript's type checking. +In the future, we may add more wrapper APIs, and may even add internal caching to those APIs to improve performance. + +:::note +Rules can still retrieve their full backing TypeScript type checker with `services.program.getTypeChecker()`. +This can be necessary for TypeScript APIs not wrapped by the parser services. +::: + +See [_Custom Rules_ on the v6 docs site preview](https://v6--typescript-eslint.netlify.app/custom-rules) for the updated documentation on creating custom rules with typescript-eslint. + +### AST Breaking Changes + +These PRs changed the AST shapes generated by typescript-eslint when parsing code. +If you author any ESLint rules that refer to the syntax mentioned by them, these are relevant to you. + +- [feat: made BaseNode.parent non-optional](https://github.com/typescript-eslint/typescript-eslint/pull/5252): makes the `node.parent` property on AST nodes non-optional (`TSESTree.Node` instead of `TSESTree.Node | undefined`). +- [fix(ast-spec): correct some incorrect ast types](https://github.com/typescript-eslint/typescript-eslint/pull/6257): applies the following changes to correct erroneous types of AST node properties: + - `ArrayExpressions`'s `elements` property can now include `null` (i.e. is now `(Expression | SpreadElement | null)[]`), for the case of sparse arrays (e.g. `[1, , 3]`). + - `MemberExpression`'s `object` property is now `Expression`, not `LeftHandSideExpression`. + - `ObjectLiteralElement` no longer allows for `MethodDefinition`. +- [fix(typescript-estree): wrap import = declaration in an export node](https://github.com/typescript-eslint/typescript-eslint/pull/5885): Exported `TSImportEqualsDeclaration` nodes are now wrapped in an `ExportNamedDeclaration` node instead of having `.isExport = true` property. +- [fix(ast-spec): remove more invalid properties](https://github.com/typescript-eslint/typescript-eslint/pull/6243): applies the following changes to remove invalid properties from AST nodes: + - `MethodDefinitionBase` no longer has a `typeParameters` property. + - `TSIndexSignature`, `TSMethodSignature`, and `TSPropertySignatureBase` no longer have an `export` property. + - `TSPropertySignatureBase` no longer has an `initializer` property. +- [fix(typescript-estree): account for namespace nesting in AST conversion](https://github.com/typescript-eslint/typescript-eslint/pull/6272): Namespaces with qualified names like `Abc.Def` now use a `TSQualifiedName` node, instead of a nested body structure. + +### ⏳ Errors on Invalid AST Parsing + +:::note +These changes only impact API consumers of typescript-eslint that work at parsing level. +If the extent of your API usage is writing custom rules, these changes don't impact you. +::: + +The `@typescript-eslint/typescript-estree` parser is by default very forgiving of invalid ASTs. +If it encounters invalid syntax, it will still attempt create an AST if possible: even if required properties of nodes don't exist. + +For example, this snippet of TypeScript code creates a `ClassDeclaration` whose `id` is `null`: + +```ts +export class {} +``` + +Invalid parsed ASTs can cause problems for downstream tools expecting AST nodes to adhere to the ESTree spec. +ESLint rules in particular tend to crash when given invalid ASTs. + +`@typescript-eslint/typescript-estree` will now throw an error when it encounters a known invalid AST such as the `export class {}` example. +This is generally the correct behavior for most parsing contexts so downstream tools don't have to work with a potentially invalid AST. + +For consumers that don't want the updated behavior of throwing on invalid ASTs, a new `allowInvalidAST` option exists to disable the throwing behavior. +Keep in mind that with it enabled, ASTs produced by typescript-eslint might not match their TSESTree type definitions. + +For more information, see: + +- The backing issue: [Parsing: strictly enforce the produced AST matches the spec and enforce most "error recovery" parsing errors](https://github.com/typescript-eslint/typescript-eslint/issues/1852) +- The implementing pull request: [feat(typescript-estree): added allowInvalidAST option to throw on invalid tokens](https://github.com/typescript-eslint/typescript-eslint/pull/6247) + +### Other Developer-Facing Breaking Changes + +- [feat: remove semantically invalid properties from TSEnumDeclaration, TSInterfaceDeclaration and TSModuleDeclaration](https://github.com/typescript-eslint/typescript-eslint/pull/4863): Removes some properties from those AST node types that should generally not have existed to begin with. +- [fix(utils): removed TRuleListener generic from the createRule](https://github.com/typescript-eslint/typescript-eslint/pull/5036): Makes `createRule`-created rules more portable in the type system. +- [feat(utils): remove (ts-)eslint-scope types](https://github.com/typescript-eslint/typescript-eslint/pull/5256): Removes no-longer-useful `TSESLintScope` types from the `@typescript-eslint/utils` package. +- [fix: rename typeParameters to typeArguments where needed](https://github.com/typescript-eslint/typescript-eslint/pull/5384): corrects the names of AST properties that were called _parameters_ instead of _arguments_. + - To recap the terminology: + - An _argument_ is something you provide to a recipient, such as a type provided explicitly to a call expression. + - A _parameter_ is how the recipient receives what you provide, such as a function declaration's generic type parameter. + - ⏳ [Enhancement: Add test-only console warnings to deprecated AST properties](https://github.com/typescript-eslint/typescript-eslint/issues/6469): The properties will include a `console.log` that triggers only in test environments, to encourage developers to move off of them. +- [feat(scope-manager): ignore ECMA version](https://github.com/typescript-eslint/typescript-eslint/pull/5889): `@typescript-eslint/scope-manager` no longer includes properties referring to `ecmaVersion`, `isES6`, or other ECMA versioning options. It instead now always assumes ESNext. +- [feat: remove partial type-information program](https://github.com/typescript-eslint/typescript-eslint/pull/6066): When user configurations don't provide a `parserOptions.project`, parser services will no longer include a `program` with incomplete type information. `program` will be `null` instead. +- [feat(experimental-utils): console.warn on import of experimental-utils](https://github.com/typescript-eslint/typescript-eslint/pull/6179): The `@typescript-eslint/experimental-utils` package has since been renamed to `@typescript-eslint/utils`. The old package name now includes a `console.warn` message to indicate you should switch to the new package name. + - As a result, the `errorOnTypeScriptSyntacticAndSemanticIssues` option will no longer be allowed if `parserOptions.project` is not provided. +- ⏳ [feat(typescript-estree): remove optionality from AST boolean properties](https://github.com/typescript-eslint/typescript-eslint/pull/6274): Switches most AST properties marked as `?: boolean` to `: boolean`, as well as some properties marked as `?:` optional to `| undefined`. This results in more predictable AST node object shapes. +- [chore(typescript-estree): remove visitor-keys backwards compat export](https://github.com/typescript-eslint/typescript-eslint/pull/6242): `visitorKeys` can now only be imported from `@typescript-eslint/visitor-keys`. Previously it was also re-exported by `@typescript-eslint/utils`. +- [feat: add package.json exports for public packages](https://github.com/typescript-eslint/typescript-eslint/pull/6458): `@typescript-eslint/*` packages now use `exports` to prevent importing internal file paths. + +## Appreciation + +We'd like to extend a sincere _thank you_ to everybody who pitched in to make typescript-eslint v6 possible. + +- Ourselves on the maintenance team: + - [Armano](https://github.com/armano2) + - [Brad Zacher](https://github.com/bradzacher) + - [James Henry](https://github.com/JamesHenry) + - [Josh Goldberg](https://github.com/JoshuaKGoldberg) + - [Joshua Chen](https://github.com/Josh-Cena) +- Community contributors whose PRs were merged into the 6.0.0 release: + + - [Bryan Mishkin](https://github.com/bmish) + - [fisker Cheung](https://github.com/fisker) + - [Juan García](https://github.com/juank1809) + - [Kevin Ball](https://github.com/kball) + - [Marek Dědič](https://github.com/marekdedic) + - [Mateusz Burzyński](https://github.com/Andarist) + + +See the [v6.0.0 milestone](https://github.com/typescript-eslint/typescript-eslint/milestone/8) for the list of issues and associated merged pull requests. + +## Supporting typescript-eslint + +If you enjoyed this blog post and/or or use typescript-eslint, please consider [supporting us on Open Collective](https://opencollective.com/typescript-eslint). +We're a small volunteer team and could use your support to make the ESLint experience on TypeScript great. +Thanks! 💖Note: This service is not intended for secure transactions such as banking, social media, email, or purchasing. 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