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    @typescript-eslint/typescript-estree
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    4.28.0 • Public • Published

    TypeScript ESTree

    A parser that converts TypeScript source code into an ESTree-compatible form

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    Getting Started

    You can find our Getting Started docs here

    About

    This parser is somewhat generic and robust, and could be used to power any use-case which requires taking TypeScript source code and producing an ESTree-compatible AST.

    In fact, it is already used within these hyper-popular open-source projects to power their TypeScript support:

    • ESLint, the pluggable linting utility for JavaScript and JSX
    • Prettier, an opinionated code formatter

    Installation

    yarn add -D @typescript-eslint/typescript-estree

    API

    Parsing

    parse(code, options)

    Parses the given string of code with the options provided and returns an ESTree-compatible AST.

    interface ParseOptions {
      /**
       * create a top-level comments array containing all comments
       */
      comment?: boolean;
    
      /**
       * An array of modules to turn explicit debugging on for.
       * - 'typescript-eslint' is the same as setting the env var `DEBUG=typescript-eslint:*`
       * - 'eslint' is the same as setting the env var `DEBUG=eslint:*`
       * - 'typescript' is the same as setting `extendedDiagnostics: true` in your tsconfig compilerOptions
       *
       * For convenience, also supports a boolean:
       * - true === ['typescript-eslint']
       * - false === []
       */
      debugLevel?: boolean | ('typescript-eslint' | 'eslint' | 'typescript')[];
    
      /**
       * Cause the parser to error if it encounters an unknown AST node type (useful for testing).
       * This case only usually occurs when TypeScript releases new features.
       */
      errorOnUnknownASTType?: boolean;
    
      /**
       * Absolute (or relative to `cwd`) path to the file being parsed.
       */
      filePath?: string;
    
      /**
       * Enable parsing of JSX.
       * For more details, see https://www.typescriptlang.org/docs/handbook/jsx.html
       *
       * NOTE: this setting does not effect known file types (.js, .jsx, .ts, .tsx, .json) because the
       * TypeScript compiler has its own internal handling for known file extensions.
       *
       * For the exact behavior, see https://github.com/typescript-eslint/typescript-eslint/tree/master/packages/parser#parseroptionsecmafeaturesjsx
       */
      jsx?: boolean;
    
      /**
       * Controls whether the `loc` information to each node.
       * The `loc` property is an object which contains the exact line/column the node starts/ends on.
       * This is similar to the `range` property, except it is line/column relative.
       */
      loc?: boolean;
    
      /*
       * Allows overriding of function used for logging.
       * When value is `false`, no logging will occur.
       * When value is not provided, `console.log()` will be used.
       */
      loggerFn?: Function | false;
    
      /**
       * Controls whether the `range` property is included on AST nodes.
       * The `range` property is a [number, number] which indicates the start/end index of the node in the file contents.
       * This is similar to the `loc` property, except this is the absolute index.
       */
      range?: boolean;
    
      /**
       * Set to true to create a top-level array containing all tokens from the file.
       */
      tokens?: boolean;
    
      /*
       * The JSX AST changed the node type for string literals
       * inside a JSX Element from `Literal` to `JSXText`.
       * When value is `true`, these nodes will be parsed as type `JSXText`.
       * When value is `false`, these nodes will be parsed as type `Literal`.
       */
      useJSXTextNode?: boolean;
    }
    
    const PARSE_DEFAULT_OPTIONS: ParseOptions = {
      comment: false,
      errorOnUnknownASTType: false,
      filePath: 'estree.ts', // or 'estree.tsx', if you pass jsx: true
      jsx: false,
      loc: false,
      loggerFn: undefined,
      range: false,
      tokens: false,
      useJSXTextNode: false,
    };
    
    declare function parse(
      code: string,
      options: ParseOptions = PARSE_DEFAULT_OPTIONS,
    ): TSESTree.Program;

    Example usage:

    import { parse } from '@typescript-eslint/typescript-estree';
    
    const code = `const hello: string = 'world';`;
    const ast = parse(code, {
      loc: true,
      range: true,
    });

    parseAndGenerateServices(code, options)

    Parses the given string of code with the options provided and returns an ESTree-compatible AST. Accepts additional options which can be used to generate type information along with the AST.

    interface ParseAndGenerateServicesOptions extends ParseOptions {
      /**
       * Causes the parser to error if the TypeScript compiler returns any unexpected syntax/semantic errors.
       */
      errorOnTypeScriptSyntacticAndSemanticIssues?: boolean;
    
      /**
       * ***EXPERIMENTAL FLAG*** - Use this at your own risk.
       *
       * Causes TS to use the source files for referenced projects instead of the compiled .d.ts files.
       * This feature is not yet optimized, and is likely to cause OOMs for medium to large projects.
       *
       * This flag REQUIRES at least TS v3.9, otherwise it does nothing.
       *
       * See: https://github.com/typescript-eslint/typescript-eslint/issues/2094
       */
      EXPERIMENTAL_useSourceOfProjectReferenceRedirect?: boolean;
    
      /**
       * When `project` is provided, this controls the non-standard file extensions which will be parsed.
       * It accepts an array of file extensions, each preceded by a `.`.
       */
      extraFileExtensions?: string[];
    
      /**
       * Absolute (or relative to `tsconfigRootDir`) path to the file being parsed.
       * When `project` is provided, this is required, as it is used to fetch the file from the TypeScript compiler's cache.
       */
      filePath?: string;
    
      /**
       * Allows the user to control whether or not two-way AST node maps are preserved
       * during the AST conversion process.
       *
       * By default: the AST node maps are NOT preserved, unless `project` has been specified,
       * in which case the maps are made available on the returned `parserServices`.
       *
       * NOTE: If `preserveNodeMaps` is explicitly set by the user, it will be respected,
       * regardless of whether or not `project` is in use.
       */
      preserveNodeMaps?: boolean;
    
      /**
       * Absolute (or relative to `tsconfigRootDir`) paths to the tsconfig(s).
       * If this is provided, type information will be returned.
       */
      project?: string | string[];
    
      /**
       * If you provide a glob (or globs) to the project option, you can use this option to ignore certain folders from
       * being matched by the globs.
       * This accepts an array of globs to ignore.
       *
       * By default, this is set to ["/node_modules/"]
       */
      projectFolderIgnoreList?: string[];
    
      /**
       * The absolute path to the root directory for all provided `project`s.
       */
      tsconfigRootDir?: string;
    
      /**
       * Instance of a TypeScript Program object to be used for type information.
       * This overrides any program or programs that would have been computed from the `project` option.
       * All linted files must be part of the provided program.
       */
      program?: import('typescript').Program;
    
      /**
       ***************************************************************************************
       * IT IS RECOMMENDED THAT YOU DO NOT USE THIS OPTION, AS IT CAUSES PERFORMANCE ISSUES. *
       ***************************************************************************************
       *
       * When passed with `project`, this allows the parser to create a catch-all, default program.
       * This means that if the parser encounters a file not included in any of the provided `project`s,
       * it will not error, but will instead parse the file and its dependencies in a new program.
       */
      createDefaultProgram?: boolean;
    
      /**
       * ESLint (and therefore typescript-eslint) is used in both "single run"/one-time contexts,
       * such as an ESLint CLI invocation, and long-running sessions (such as continuous feedback
       * on a file in an IDE).
       *
       * When typescript-eslint handles TypeScript Program management behind the scenes, this distinction
       * is important because there is significant overhead to managing the so called Watch Programs
       * needed for the long-running use-case.
       *
       * When allowAutomaticSingleRunInference is enabled, we will use common heuristics to infer
       * whether or not ESLint is being used as part of a single run.
       */
      allowAutomaticSingleRunInference?: boolean;
    }
    
    interface ParserServices {
      program: ts.Program;
      esTreeNodeToTSNodeMap: WeakMap<TSESTree.Node, ts.Node | ts.Token>;
      tsNodeToESTreeNodeMap: WeakMap<ts.Node | ts.Token, TSESTree.Node>;
      hasFullTypeInformation: boolean;
    }
    
    interface ParseAndGenerateServicesResult<T extends TSESTreeOptions> {
      ast: TSESTree.Program;
      services: ParserServices;
    }
    
    const PARSE_AND_GENERATE_SERVICES_DEFAULT_OPTIONS: ParseOptions = {
      ...PARSE_DEFAULT_OPTIONS,
      errorOnTypeScriptSyntacticAndSemanticIssues: false,
      extraFileExtensions: [],
      preserveNodeMaps: false, // or true, if you do not set this, but pass `project`
      project: undefined,
      projectFolderIgnoreList: ['/node_modules/'],
      tsconfigRootDir: process.cwd(),
    };
    
    declare function parseAndGenerateServices(
      code: string,
      options: ParseOptions = PARSE_DEFAULT_OPTIONS,
    ): ParseAndGenerateServicesResult;

    Example usage:

    import { parseAndGenerateServices } from '@typescript-eslint/typescript-estree';
    
    const code = `const hello: string = 'world';`;
    const { ast, services } = parseAndGenerateServices(code, {
      filePath: '/some/path/to/file/foo.ts',
      loc: true,
      project: './tsconfig.json',
      range: true,
    });

    parseWithNodeMaps(code, options)

    Parses the given string of code with the options provided and returns both the ESTree-compatible AST as well as the node maps. This allows you to work with both ASTs without the overhead of types that may come with parseAndGenerateServices.

    interface ParseWithNodeMapsResult<T extends TSESTreeOptions> {
      ast: TSESTree.Program;
      esTreeNodeToTSNodeMap: ParserServices['esTreeNodeToTSNodeMap'];
      tsNodeToESTreeNodeMap: ParserServices['tsNodeToESTreeNodeMap'];
    }
    
    declare function parseWithNodeMaps(
      code: string,
      options: ParseOptions = PARSE_DEFAULT_OPTIONS,
    ): ParseWithNodeMapsResult;

    Example usage:

    import { parseWithNodeMaps } from '@typescript-eslint/typescript-estree';
    
    const code = `const hello: string = 'world';`;
    const { ast, esTreeNodeToTSNodeMap, tsNodeToESTreeNodeMap } = parseWithNodeMaps(
      code,
      {
        loc: true,
        range: true,
      },
    );

    TSESTree, AST_NODE_TYPES and AST_TOKEN_TYPES

    Types for the AST produced by the parse functions.

    • TSESTree is a namespace which contains object types representing all of the AST Nodes produced by the parser.
    • AST_NODE_TYPES is an enum which provides the values for every single AST node's type property.
    • AST_TOKEN_TYPES is an enum which provides the values for every single AST token's type property.

    Utilities

    createProgram(configFile, projectDirectory)

    This serves as a utility method for users of the ParseOptions.program feature to create a TypeScript program instance from a config file.

    declare function createProgram(
      configFile: string,
      projectDirectory: string = process.cwd(),
    ): import('typescript').Program;

    Example usage:

    const tsESTree = require('@typescript-eslint/typescript-estree');
    
    const program = tsESTree.createProgram('tsconfig.json');
    const code = `const hello: string = 'world';`;
    const { ast, services } = parseAndGenerateServices(code, {
      filePath: '/some/path/to/file/foo.ts',
      loc: true,
      program,
      range: true,
    });

    Supported TypeScript Version

    See the Supported TypeScript Version section in the project root.

    If you use a non-supported version of TypeScript, the parser will log a warning to the console.

    Please ensure that you are using a supported version before submitting any issues/bug reports.

    Reporting Issues

    Please check the current list of open and known issues and ensure the issue has not been reported before. When creating a new issue provide as much information about your environment as possible. This includes:

    • TypeScript version
    • The typescript-estree version

    AST Alignment Tests

    A couple of years after work on this parser began, the TypeScript Team at Microsoft began officially supporting TypeScript parsing via Babel.

    I work closely with the TypeScript Team and we are gradually aligning the AST of this project with the one produced by Babel's parser. To that end, I have created a full test harness to compare the ASTs of the two projects which runs on every PR, please see the code for more details.

    Debugging

    If you encounter a bug with the parser that you want to investigate, you can turn on the debug logging via setting the environment variable: DEBUG=typescript-eslint:*. I.e. in this repo you can run: DEBUG=typescript-eslint:* yarn lint.

    License

    TypeScript ESTree inherits from the the original TypeScript ESLint Parser license, as the majority of the work began there. It is licensed under a permissive BSD 2-clause license.

    Contributing

    See the contributing guide here

    Install

    npm i @typescript-eslint/typescript-estree

    DownloadsWeekly Downloads

    15,772,800

    Version

    4.28.0

    License

    BSD-2-Clause

    Unpacked Size

    501 kB

    Total Files

    92

    Last publish

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