Update: add class fields (refs eslint/eslint#14343) (#486)

* Update: add ES2022 class features support (refs eslint/eslint#14343)

* update README.md

* update tools and add docs for adding new syntax

* add dist

* upgrade eslint-visitor-keys

* Revert "add dist"

This reverts commit 3e9caa7.

* add npm prepare script

* Update CONTRIBUTING.md

Co-authored-by: 薛定谔的猫 <weiran.zsd@outlook.com>

* update CONTRIBUTING.md

* fix for JSON incompatible values

* Apply suggestions from code review

Co-authored-by: 薛定谔的猫 <weiran.zsd@outlook.com>
Co-authored-by: Nicholas C. Zakas <nicholas@nczconsulting.com>

.eslintignore

@@ -1,3 +1,5 @@
 /node_modules
 /tests/fixtures
-/tools
+/tools/*
+!/tools/update-ecma-version-tests.js
+/dist

.eslintrc.cjs

@@ -4,17 +4,30 @@ module.exports = {
     root: true,
     extends: "eslint",
     env: {
-        es6: true
+        es2020: true
+    },
+    parserOptions: {
+        ecmaVersion: 2020,
+        sourceType: "module"
     },
     overrides: [
         {
-            files: ["tests/lib/**"],
+            files: ["*.cjs"],
             parserOptions: {
-                ecmaVersion: 2020
-            },
+                sourceType: "script"
+            }
+        },
+        {
+            files: ["tests/lib/**"],
             env: {
                 mocha: true
             }
+        },
+        {
+            files: ["tools/**"],
+            rules: {
+                "no-console": "off"
+            }
         }
     ]
 };

CONTRIBUTING.md

@@ -6,3 +6,17 @@ Please sign the [jQuery Foundation Contributor License Agreement](https://contri
 
 Our full contribution guidelines can be found at:
 <http://eslint.org/docs/developer-guide/contributing/>
+
+# How to upgrade `acorn` to support new syntax
+
+1. `npm install acorn@latest`
+1. If a new `ecmaVersion` value is added, update `SUPPORTED_VERSIONS` constant in `lib/options.js` and tests in `tests/lib/supported-ecmaversions.js`.
+1. If new token types are added, update `lib/token-translator.js` file to translate the tokens.
+1. Add tests in `tests/fixtures/ecma-version/<ecma-vesion>/`.
+    - Add a directory named the new syntax name.
+    - Add `valid-<test-case-name>.src.js` files for parseable codes.
+    - Add `invalid-<test-case-name>.src.js` files for syntax error codes.
+    - Run `node tools/update-ecma-version-tests.js <ecma-vesion>` command to generate `<name>.result.js` files.
+    - Check the `<name>.result.js` files are expected results.
+1. Update `README.md`.
+1. Send a pull request.

README.md

@@ -141,7 +141,7 @@ const options = {
     tokens: false,
 
     // Set to 3, 5, 6, 7, 8, 9, 10, 11, or 12 to specify the version of ECMAScript syntax you want to use.
-    // You can also set to 2015 (same as 6), 2016 (same as 7), 2017 (same as 8), 2018 (same as 9), 2019 (same as 10), 2020 (same as 11), or 2021 (same as 12) to use the year-based naming.
+    // You can also set to 2015 (same as 6), 2016 (same as 7), 2017 (same as 8), 2018 (same as 9), 2019 (same as 10), 2020 (same as 11), 2021 (same as 12), or 2022 (same as 13) to use the year-based naming.
     // You can also set "latest" (the default) to use the most recently supported version.
     ecmaVersion: 5,
 
@@ -229,12 +229,13 @@ We are building on top of Acorn, however, so that we can contribute back and hel
 
 ### What ECMAScript features do you support?
 
-Espree supports all ECMAScript 2020 features and partially supports ECMAScript 2021 features.
+Espree supports all ECMAScript 2021 features and partially supports ECMAScript 2022 features.
 
-Because ECMAScript 2021 is still under development, we are implementing features as they are finalized. Currently, Espree supports:
+Because ECMAScript 2022 is still under development, we are implementing features as they are finalized. Currently, Espree supports:
 
-* [Logical Assignment Operators](https://github.com/tc39/proposal-logical-assignment)
-* [Numeric Separators](https://github.com/tc39/proposal-numeric-separator)
+* [Class instance fields](https://github.com/tc39/proposal-class-fields)
+* [Class private instance methods and accessors](https://github.com/tc39/proposal-private-methods)
+* [Class static fields, static private methods and accessors](https://github.com/tc39/proposal-static-class-features)
 
 See [finished-proposals.md](https://github.com/tc39/proposals/blob/master/finished-proposals.md) to know what features are finalized.
 

lib/options.js

@@ -16,7 +16,8 @@ const SUPPORTED_VERSIONS = [
     9,
     10,
     11,
-    12
+    12,
+    13
 ];
 
 /**

lib/token-translator.js

@@ -20,6 +20,7 @@ const Token = {
     Boolean: "Boolean",
     EOF: "<end>",
     Identifier: "Identifier",
+    PrivateIdentifier: "PrivateIdentifier",
     Keyword: "Keyword",
     Null: "Null",
     Numeric: "Numeric",
@@ -114,6 +115,9 @@ TokenTranslator.prototype = {
                 token.type = Token.Keyword;
             }
 
+        } else if (type === tt.privateId) {
+            token.type = Token.PrivateIdentifier;
+
         } else if (type === tt.semi || type === tt.comma ||
                  type === tt.parenL || type === tt.parenR ||
                  type === tt.braceL || type === tt.braceR ||

package.json

@@ -33,7 +33,7 @@
   "dependencies": {
     "acorn": "^8.2.2",
     "acorn-jsx": "^5.3.1",
-    "eslint-visitor-keys": "^2.0.0"
+    "eslint-visitor-keys": "^2.1.0"
   },
   "devDependencies": {
     "@rollup/plugin-commonjs": "^17.1.0",

tests/fixtures/ecma-version/13/class-fields/invalid-delete-private-optional.result.js

@@ -0,0 +1,6 @@
+export default {
+    "index": 28,
+    "lineNumber": 3,
+    "column": 11,
+    "message": "Private fields can not be deleted"
+};

tests/fixtures/ecma-version/13/class-fields/invalid-delete-private-optional.src.js

@@ -0,0 +1,4 @@
+class C {
+    #a;
+    f() { delete this?.#a }
+}

tests/fixtures/ecma-version/13/class-fields/invalid-delete-private.result.js

@@ -0,0 +1,6 @@
+export default {
+    "index": 28,
+    "lineNumber": 3,
+    "column": 11,
+    "message": "Private fields can not be deleted"
+};

tests/fixtures/ecma-version/13/class-fields/invalid-delete-private.src.js

@@ -0,0 +1,4 @@
+class C {
+    #a;
+    f() { delete this.#a }
+}

tests/fixtures/ecma-version/13/class-fields/invalid-init-arguments.result.js

@@ -0,0 +1,6 @@
+export default {
+    "index": 43,
+    "lineNumber": 3,
+    "column": 15,
+    "message": "Cannot use 'arguments' in class field initializer"
+};

tests/fixtures/ecma-version/13/class-fields/invalid-init-arguments.src.js

@@ -0,0 +1,5 @@
+function f() {
+    class C {
+        aaa = arguments
+    }
+}

tests/fixtures/ecma-version/13/class-fields/invalid-init-arrow-arguments.result.js

@@ -0,0 +1,6 @@
+export default {
+    "index": 49,
+    "lineNumber": 3,
+    "column": 21,
+    "message": "Cannot use 'arguments' in class field initializer"
+};

tests/fixtures/ecma-version/13/class-fields/invalid-init-arrow-arguments.src.js

@@ -0,0 +1,5 @@
+function f() {
+    class C {
+        aaa = () => arguments
+    }
+}

tests/fixtures/ecma-version/13/class-fields/invalid-init-yield.result.js

@@ -0,0 +1,6 @@
+export default {
+    "index": 333,
+    "lineNumber": 7,
+    "column": 15,
+    "message": "The keyword 'yield' is reserved"
+};

tests/fixtures/ecma-version/13/class-fields/invalid-init-yield.src.js

@@ -0,0 +1,9 @@
+function* f() {
+    class C {
+        // `yield` is an identifier reference in field initializers even if it's in a generator function.
+        // But `yield` as identifier references is disallowed in strict mode.
+        // And the inside of classes is always strict mode.
+        // Therefore this is a syntax error.
+        aaa = yield
+    }
+}

tests/fixtures/ecma-version/13/class-fields/invalid-member-private-undef.result.js

@@ -0,0 +1,6 @@
+export default {
+    "index": 41,
+    "lineNumber": 4,
+    "column": 14,
+    "message": "Private field '#b' must be declared in an enclosing class"
+};

tests/fixtures/ecma-version/13/class-fields/invalid-member-private-undef.src.js

@@ -0,0 +1,6 @@
+class C {
+    #a;
+    f() {
+        this.#b
+    }
+}

tests/fixtures/ecma-version/13/class-fields/invalid-member-super-private.result.js

@@ -0,0 +1,6 @@
+export default {
+    "index": 49,
+    "lineNumber": 3,
+    "column": 17,
+    "message": "Unexpected token #foo"
+};

tests/fixtures/ecma-version/13/class-fields/invalid-member-super-private.src.js

@@ -0,0 +1,4 @@
+class C extends Base {
+    #foo;
+    f() { super.#foo }
+}

tests/fixtures/ecma-version/13/class-fields/invalid-private-constructor.result.js

@@ -0,0 +1,6 @@
+export default {
+    "index": 14,
+    "lineNumber": 2,
+    "column": 5,
+    "message": "Classes can't have an element named '#constructor'"
+};

tests/fixtures/ecma-version/13/class-fields/invalid-private-constructor.src.js

@@ -0,0 +1,3 @@
+class C {
+    #constructor = () => {}
+}

tests/fixtures/ecma-version/13/class-fields/invalid-private-dupelicate.result.js

@@ -0,0 +1,6 @@
+export default {
+    "index": 22,
+    "lineNumber": 3,
+    "column": 5,
+    "message": "Identifier '#a' has already been declared"
+};

tests/fixtures/ecma-version/13/class-fields/invalid-private-dupelicate.src.js

@@ -0,0 +1,4 @@
+class C {
+    #a;
+    #a;
+}

tests/fixtures/ecma-version/13/class-fields/invalid-public-constructor.result.js

@@ -0,0 +1,6 @@
+export default {
+    "index": 14,
+    "lineNumber": 2,
+    "column": 5,
+    "message": "Classes can't have a field named 'constructor'"
+};

tests/fixtures/ecma-version/13/class-fields/invalid-public-constructor.src.js

@@ -0,0 +1,3 @@
+class C {
+    constructor = () => {}
+}

tests/fixtures/ecma-version/13/class-fields/mixed-init-await.module-result.js

@@ -0,0 +1,6 @@
+export default {
+    "index": 304,
+    "lineNumber": 6,
+    "column": 15,
+    "message": "Cannot use keyword 'await' outside an async function"
+};