feat: try all known parsers at runtime if no parser specific

Author: JounQin

.eslintrc.js

@@ -10,18 +10,13 @@ tsNode.register({
 module.exports = {
   root: true,
   extends: ['@1stg/eslint-config/recommended'],
-  overrides: [
-    {
-      files: '*.ts',
-      settings: {
-        node: {
-          allowModules: ['@babel/types', 'estree', 'unist'],
-        },
-      },
-      rules: {
-        '@typescript-eslint/no-unnecessary-condition': 0,
-        '@typescript-eslint/unbound-method': 0, // See https://github.com/typescript-eslint/typescript-eslint/issues/636
-      },
+  settings: {
+    node: {
+      allowModules: ['@babel/types', 'estree', 'unist'],
     },
-  ],
+  },
+  rules: {
+    '@typescript-eslint/no-unnecessary-condition': 0,
+    '@typescript-eslint/unbound-method': 0, // See https://github.com/typescript-eslint/typescript-eslint/issues/636
+  },
 }

packages/eslint-mdx/src/helper.ts

@@ -1,6 +1,6 @@
 /// <reference path="../typings.d.ts" />
 
-import { AST } from 'eslint'
+import { AST, Linter } from 'eslint'
 import { parse as esParse } from 'espree'
 import { SourceLocation } from 'estree'
 import { Position } from 'unist'
@@ -40,24 +40,31 @@ export const normalizeParser = (parser?: ParserOptions['parser']) => {
     if (typeof parser !== 'function') {
       throw new TypeError(`Invalid custom parser for \`eslint-mdx\`: ${parser}`)
     }
-  } else {
-    // try to load FALLBACK_PARSERS automatically
-    for (const fallback of FALLBACK_PARSERS) {
-      try {
-        // eslint-disable-next-line @typescript-eslint/no-require-imports,@typescript-eslint/no-var-requires
-        const fallbackParser = require(fallback)
-        /* istanbul ignore next */
-        parser = fallbackParser.parseForESLint || fallbackParser.parse
-        break
-      } catch (e) {}
-    }
 
-    if (typeof parser !== 'function') {
-      parser = esParse as ParserFn
-    }
+    return [parser]
+  }
+
+  const parsers = [esParse as ParserFn]
+
+  // try to load FALLBACK_PARSERS automatically
+  for (const fallback of FALLBACK_PARSERS) {
+    try {
+      // eslint-disable-next-line @typescript-eslint/no-require-imports,@typescript-eslint/no-var-requires
+      const fallbackParser: Linter.ParserModule = require(fallback)
+      /* istanbul ignore next */
+      const parserFn =
+        'parseForESLint' in fallbackParser
+          ? fallbackParser.parseForESLint
+          : fallbackParser.parse
+      /* istanbul ignore else */
+      if (parserFn) {
+        parsers.unshift(parserFn)
+      }
+      break
+    } catch (e) {}
   }
 
-  return parser
+  return parsers
 }
 
 export const normalizePosition = (

packages/eslint-mdx/src/parser.ts

@@ -48,7 +48,7 @@ const OFFSET = JSX_WRAPPER_START.length
 
 export class Parser {
   // @internal
-  private _parser: ParserFn
+  private _parsers: ParserFn[]
 
   // @internal
   private _ast: AST.Program
@@ -191,14 +191,32 @@ export class Parser {
 
   // @internal
   private _eslintParse(code: string, options: ParserOptions) {
-    if (!this._parser || options.parser !== this._options.parser) {
-      this._parser = normalizeParser(options.parser)
+    if (!this._parsers || options.parser !== this._options.parser) {
+      this._parsers = normalizeParser(options.parser)
     }
+
     /* istanbul ignore else */
     if (options.filePath && this._options !== options) {
       Object.assign(this._options, options)
     }
-    const program = this._parser(code, this._options)
+
+    let program: ReturnType<ParserFn>
+    let parseError: Error
+    for (const parser of this._parsers) {
+      try {
+        program = parser(code, this._options)
+        break
+      } catch (e) {
+        if (!parseError) {
+          parseError = e
+        }
+      }
+    }
+
+    if (!program && parseError) {
+      throw parseError
+    }
+
     /* istanbul ignore next */
     return ('ast' in program && program.ast
       ? program

test/parser.test.ts

@@ -141,7 +141,7 @@ describe('parser', () => {
 
   it('should fallback to espree if no preferred parsers found', () => {
     jest.mock('@typescript-eslint/parser', noop).mock('babel-eslint', noop)
-    expect(normalizeParser()).toBe(parse)
+    expect(normalizeParser()).toContain(parse)
     jest.unmock('@typescript-eslint/parser').unmock('babel-eslint')
   })