feat: support 'latest' as ecmaVersion

packages/parser/README.md

@@ -53,7 +53,7 @@ interface ParserOptions {
     jsx?: boolean;
     globalReturn?: boolean;
   };
-  ecmaVersion?: number;
+  ecmaVersion?: number | 'latest';
 
   jsxPragma?: string | null;
   jsxFragmentName?: string | null;
@@ -97,12 +97,13 @@ This options allows you to tell the parser if you want to allow global `return`
 
 Default `2018`.
 
-Accepts any valid ECMAScript version number:
+Accepts any valid ECMAScript version number or `'latest'`:
 
 - A version: es3, es5, es6, es7, es8, es9, es10, es11, ..., or
 - A year: es2015, es2016, es2017, es2018, es2019, es2020, ...
+- `latest`
 
-The value **must** be a number - so do not include the `es` prefix.
+When it's a version or a year, the value **must** be a number - so do not include the `es` prefix.
 
 Specifies the version of ECMAScript syntax you want to use. This is used by the parser to determine how to perform scope analysis, and it affects the default
 

packages/parser/tests/lib/parser.ts

@@ -18,6 +18,11 @@ describe('parser', () => {
     expect(() => parseForESLint(code, null)).not.toThrow();
   });
 
+  it("parseForESLint() should work if options.ecmaVersion is `'latest'`", () => {
+    const code = 'const valid = true;';
+    expect(() => parseForESLint(code, { ecmaVersion: 'latest' })).not.toThrow();
+  });
+
   it('parseAndGenerateServices() should be called with options', () => {
     const code = 'const valid = true;';
     const spy = jest.spyOn(typescriptESTree, 'parseAndGenerateServices');

packages/scope-manager/src/ScopeManager.ts

@@ -26,7 +26,7 @@ interface ScopeManagerOptions {
   globalReturn?: boolean;
   sourceType?: 'module' | 'script';
   impliedStrict?: boolean;
-  ecmaVersion?: number;
+  ecmaVersion?: number | 'latest';
 }
 
 class ScopeManager {
@@ -76,11 +76,17 @@ class ScopeManager {
     return this.#options.impliedStrict === true;
   }
   public isStrictModeSupported(): boolean {
-    return this.#options.ecmaVersion != null && this.#options.ecmaVersion >= 5;
+    return (
+      this.#options.ecmaVersion === 'latest' ||
+      (this.#options.ecmaVersion != null && this.#options.ecmaVersion >= 5)
+    );
   }
 
   public isES6(): boolean {
-    return this.#options.ecmaVersion != null && this.#options.ecmaVersion >= 6;
+    return (
+      this.#options.ecmaVersion === 'latest' ||
+      (this.#options.ecmaVersion != null && this.#options.ecmaVersion >= 6)
+    );
   }
 
   /**

packages/scope-manager/src/analyze.ts

@@ -82,6 +82,10 @@ const DEFAULT_OPTIONS: Required<AnalyzeOptions> = {
 };
 
 function mapEcmaVersion(version: EcmaVersion | undefined): Lib {
+  if (version === 'latest') {
+    return 'esnext';
+  }
+
   if (version == null || version === 3 || version === 5) {
     return 'es5';
   }

packages/scope-manager/tests/eslint-scope/map-ecma-version.test.ts

@@ -31,11 +31,18 @@ describe('ecma version mapping', () => {
   it("should map to 'es2018' when undefined", () => {
     expectMapping(undefined, 'es2018');
   });
+
+  it("should map to 'esnext' when 'latest'", () => {
+    expectMapping('latest', 'esnext');
+  });
 });
 
 const fakeNode = {} as unknown as TSESTree.Node;
 
-function expectMapping(ecmaVersion: number | undefined, lib: Lib): void {
+function expectMapping(
+  ecmaVersion: number | undefined | 'latest',
+  lib: Lib,
+): void {
   (Referencer as jest.Mock).mockClear();
   analyze(fakeNode, { ecmaVersion: ecmaVersion as EcmaVersion });
   expect(Referencer).toHaveBeenCalledWith(

packages/types/src/parser-options.ts

@@ -17,7 +17,8 @@ type EcmaVersion =
   | 2017
   | 2018
   | 2019
-  | 2020;
+  | 2020
+  | 'latest';
 
 type SourceType = 'script' | 'module';