Add accessor contextual modifier to class properties

Adds the `accessor` modifier to public and private class properties.
This is the first part of the implementation of the latest version of
the decorators proposal: https://github.com/tc39/proposal-decorators

The keyword is outlined here in the README: https://github.com/tc39/proposal-decorators#class-auto-accessors

It was unclear to me if there is any feature flagging that should be
added in here at the parser level, or if that happens at a later stage.
I know that decorators would refuse to parse, for instance, unless you
have the decorators proposal enabled, but it seems like that might
happen in a different layer?

packages/babel-parser/ast/spec.md

@@ -1235,6 +1235,7 @@ interface ClassProperty <: Node {
   value: Expression;
   static: boolean;
   computed: boolean;
+  accessor: boolean;
 }
 ```
 

packages/babel-parser/package.json

@@ -4,7 +4,7 @@
   "description": "A JavaScript parser",
   "author": "The Babel Team (https://babel.dev/team)",
   "homepage": "https://babel.dev/docs/en/next/babel-parser",
-  "bugs": "https://github.com/babel/babel/issues?utf8=%E2%9C%93&q=is%3Aissue+label%3A%22pkg%3A+parser+%28babylon%29%22+is%3Aopen",
+  "bugs": "https://github.com/babel/babel/issues?utf8=%E2%9C%93&q=is%3Aissue+label%3A%22pkg%3A+parser+%28bab;lon%29%22+is%3Aopen",
   "license": "MIT",
   "publishConfig": {
     "access": "public"

packages/babel-parser/src/parser/statement.js

@@ -1373,6 +1373,7 @@ export default class StatementParser extends ExpressionParser {
       prop.computed = false;
       prop.key = key;
       prop.static = false;
+      prop.accessor = false;
       classBody.body.push(this.parseClassProperty(prop));
       return true;
     }
@@ -1409,10 +1410,11 @@ export default class StatementParser extends ExpressionParser {
   ) {
     const publicMethod: $FlowSubtype<N.ClassMethod> = member;
     const privateMethod: $FlowSubtype<N.ClassPrivateMethod> = member;
-    const publicProp: $FlowSubtype<N.ClassMethod> = member;
-    const privateProp: $FlowSubtype<N.ClassPrivateMethod> = member;
+    const publicProp: $FlowSubtype<N.ClassProperty> = member;
+    const privateProp: $FlowSubtype<N.ClassPrivateProperty> = member;
 
     const method: typeof publicMethod | typeof privateMethod = publicMethod;
+    const prop: typeof publicProp | typeof privateProp = publicProp;
     const publicMember: typeof publicMethod | typeof publicProp = publicMethod;
 
     member.static = isStatic;
@@ -1486,6 +1488,8 @@ export default class StatementParser extends ExpressionParser {
         allowsDirectSuper,
       );
     } else if (this.isClassProperty()) {
+      prop.accessor = false;
+
       if (isPrivate) {
         this.pushClassPrivateProperty(classBody, privateProp);
       } else {
@@ -1563,6 +1567,24 @@ export default class StatementParser extends ExpressionParser {
       }
 
       this.checkGetterSetterParams(publicMethod);
+    } else if (
+      isContextual &&
+      key.name === "accessor" &&
+      !this.isLineTerminator()
+    ) {
+      this.resetPreviousNodeTrailingComments(key);
+
+      // The so-called parsed name would have been "get/set": get the real name.
+      const isPrivate = this.match(tt.privateName);
+      this.parseClassElementName(publicProp);
+
+      prop.accessor = true;
+
+      if (isPrivate) {
+        this.pushClassPrivateProperty(classBody, privateProp);
+      } else {
+        this.pushClassProperty(classBody, publicProp);
+      }
     } else if (this.isLineTerminator()) {
       // an uninitialized class property (due to ASI, since we don't otherwise recognize the next token)
       if (isPrivate) {

packages/babel-parser/src/types.js

@@ -813,6 +813,7 @@ export type ClassProperty = ClassMemberBase &
     type: "ClassProperty",
     key: Expression,
     value: ?Expression, // TODO: Not in spec that this is nullable.
+    accessor: boolean,
 
     typeAnnotation?: ?TypeAnnotationBase, // TODO: Not in spec
     variance?: ?FlowVariance, // TODO: Not in spec
@@ -828,6 +829,7 @@ export type ClassPrivateProperty = NodeBase & {
   value: ?Expression, // TODO: Not in spec that this is nullable.
   static: boolean,
   computed: false,
+  accessor: boolean,
 
   // Flow and Typescript
   typeAnnotation?: ?TypeAnnotationBase,

packages/babel-parser/test/fixtures/core/opts/private-name-tokens-true-babel-7/output.json

@@ -33,6 +33,7 @@
                   "name": "p"
                 }
               },
+              "accessor": false,
               "value": null
             }
           ]

packages/babel-parser/test/fixtures/es2022/class-private-methods/combined/output.json

@@ -30,6 +30,7 @@
                 "name": "a"
               },
               "computed": false,
+              "accessor": false,
               "value": {
                 "type": "NumericLiteral",
                 "start":18,"end":19,"loc":{"start":{"line":2,"column":6},"end":{"line":2,"column":7}},
@@ -98,6 +99,7 @@
                   "name": "b"
                 }
               },
+              "accessor": false,
               "value": {
                 "type": "NumericLiteral",
                 "start":61,"end":62,"loc":{"start":{"line":8,"column":7},"end":{"line":8,"column":8}},
@@ -222,12 +224,12 @@
                           "start":139,"end":143,"loc":{"start":{"line":14,"column":11},"end":{"line":14,"column":15},"identifierName":"Math"},
                           "name": "Math"
                         },
+                        "computed": false,
                         "property": {
                           "type": "Identifier",
                           "start":144,"end":150,"loc":{"start":{"line":14,"column":16},"end":{"line":14,"column":22},"identifierName":"random"},
                           "name": "random"
-                        },
-                        "computed": false
+                        }
                       },
                       "arguments": []
                     }

packages/babel-parser/test/fixtures/es2022/class-private-names-duplicated/instance-field-instance-field/output.json

@@ -36,6 +36,7 @@
                   "name": "x"
                 }
               },
+              "accessor": false,
               "value": {
                 "type": "NumericLiteral",
                 "start":17,"end":18,"loc":{"start":{"line":2,"column":7},"end":{"line":2,"column":8}},
@@ -59,6 +60,7 @@
                   "name": "x"
                 }
               },
+              "accessor": false,
               "value": {
                 "type": "NumericLiteral",
                 "start":27,"end":28,"loc":{"start":{"line":3,"column":7},"end":{"line":3,"column":8}},

packages/babel-parser/test/fixtures/es2022/class-private-names-duplicated/instance-field-instance-get/output.json

@@ -36,6 +36,7 @@
                   "name": "x"
                 }
               },
+              "accessor": false,
               "value": {
                 "type": "NumericLiteral",
                 "start":17,"end":18,"loc":{"start":{"line":2,"column":7},"end":{"line":2,"column":8}},

packages/babel-parser/test/fixtures/es2022/class-private-names-duplicated/instance-field-instance-method/output.json

@@ -36,6 +36,7 @@
                   "name": "x"
                 }
               },
+              "accessor": false,
               "value": {
                 "type": "NumericLiteral",
                 "start":17,"end":18,"loc":{"start":{"line":2,"column":7},"end":{"line":2,"column":8}},

packages/babel-parser/test/fixtures/es2022/class-private-names-duplicated/instance-field-instance-set/output.json

@@ -36,6 +36,7 @@
                   "name": "x"
                 }
               },
+              "accessor": false,
               "value": {
                 "type": "NumericLiteral",
                 "start":17,"end":18,"loc":{"start":{"line":2,"column":7},"end":{"line":2,"column":8}},

packages/babel-parser/test/fixtures/es2022/class-private-names-duplicated/instance-field-static-field/output.json

@@ -36,6 +36,7 @@
                   "name": "x"
                 }
               },
+              "accessor": false,
               "value": {
                 "type": "NumericLiteral",
                 "start":17,"end":18,"loc":{"start":{"line":2,"column":7},"end":{"line":2,"column":8}},
@@ -59,6 +60,7 @@
                   "name": "x"
                 }
               },
+              "accessor": false,
               "value": {
                 "type": "NumericLiteral",
                 "start":34,"end":35,"loc":{"start":{"line":3,"column":14},"end":{"line":3,"column":15}},

packages/babel-parser/test/fixtures/es2022/class-private-names-duplicated/instance-field-static-get/output.json

@@ -36,6 +36,7 @@
                   "name": "x"
                 }
               },
+              "accessor": false,
               "value": {
                 "type": "NumericLiteral",
                 "start":17,"end":18,"loc":{"start":{"line":2,"column":7},"end":{"line":2,"column":8}},

packages/babel-parser/test/fixtures/es2022/class-private-names-duplicated/instance-field-static-method/output.json

@@ -36,6 +36,7 @@
                   "name": "x"
                 }
               },
+              "accessor": false,
               "value": {
                 "type": "NumericLiteral",
                 "start":17,"end":18,"loc":{"start":{"line":2,"column":7},"end":{"line":2,"column":8}},

packages/babel-parser/test/fixtures/es2022/class-private-names-duplicated/instance-field-static-set/output.json

@@ -36,6 +36,7 @@
                   "name": "x"
                 }
               },
+              "accessor": false,
               "value": {
                 "type": "NumericLiteral",
                 "start":17,"end":18,"loc":{"start":{"line":2,"column":7},"end":{"line":2,"column":8}},

packages/babel-parser/test/fixtures/es2022/class-private-names-duplicated/instance-get-instance-field/output.json

@@ -62,6 +62,7 @@
                   "name": "x"
                 }
               },
+              "accessor": false,
               "value": {
                 "type": "NumericLiteral",
                 "start":31,"end":32,"loc":{"start":{"line":3,"column":7},"end":{"line":3,"column":8}},

packages/babel-parser/test/fixtures/es2022/class-private-names-duplicated/instance-get-static-field/output.json

@@ -62,6 +62,7 @@
                   "name": "x"
                 }
               },
+              "accessor": false,
               "value": {
                 "type": "NumericLiteral",
                 "start":38,"end":39,"loc":{"start":{"line":3,"column":14},"end":{"line":3,"column":15}},

packages/babel-parser/test/fixtures/es2022/class-private-names-duplicated/instance-method-instance-field/output.json

@@ -61,6 +61,7 @@
                   "name": "x"
                 }
               },
+              "accessor": false,
               "value": {
                 "type": "NumericLiteral",
                 "start":27,"end":28,"loc":{"start":{"line":3,"column":7},"end":{"line":3,"column":8}},

packages/babel-parser/test/fixtures/es2022/class-private-names-duplicated/instance-method-static-field/output.json

@@ -61,6 +61,7 @@
                   "name": "x"
                 }
               },
+              "accessor": false,
               "value": {
                 "type": "NumericLiteral",
                 "start":34,"end":35,"loc":{"start":{"line":3,"column":14},"end":{"line":3,"column":15}},

packages/babel-parser/test/fixtures/es2022/class-private-names-duplicated/instance-set-instance-field/output.json

@@ -68,6 +68,7 @@
                   "name": "x"
                 }
               },
+              "accessor": false,
               "value": {
                 "type": "NumericLiteral",
                 "start":32,"end":33,"loc":{"start":{"line":3,"column":7},"end":{"line":3,"column":8}},

packages/babel-parser/test/fixtures/es2022/class-private-names-duplicated/instance-set-static-field/output.json

@@ -68,6 +68,7 @@
                   "name": "x"
                 }
               },
+              "accessor": false,
               "value": {
                 "type": "NumericLiteral",
                 "start":39,"end":40,"loc":{"start":{"line":3,"column":14},"end":{"line":3,"column":15}},

packages/babel-parser/test/fixtures/es2022/class-private-names-duplicated/static-field-instance-field/output.json

@@ -36,6 +36,7 @@
                   "name": "x"
                 }
               },
+              "accessor": false,
               "value": {
                 "type": "NumericLiteral",
                 "start":24,"end":25,"loc":{"start":{"line":2,"column":14},"end":{"line":2,"column":15}},
@@ -59,6 +60,7 @@
                   "name": "x"
                 }
               },
+              "accessor": false,
               "value": {
                 "type": "NumericLiteral",
                 "start":34,"end":35,"loc":{"start":{"line":3,"column":7},"end":{"line":3,"column":8}},

packages/babel-parser/test/fixtures/es2022/class-private-names-duplicated/static-field-instance-get/output.json

@@ -36,6 +36,7 @@
                   "name": "x"
                 }
               },
+              "accessor": false,
               "value": {
                 "type": "NumericLiteral",
                 "start":24,"end":25,"loc":{"start":{"line":2,"column":14},"end":{"line":2,"column":15}},

packages/babel-parser/test/fixtures/es2022/class-private-names-duplicated/static-field-instance-method/output.json

@@ -36,6 +36,7 @@
                   "name": "x"
                 }
               },
+              "accessor": false,
               "value": {
                 "type": "NumericLiteral",
                 "start":24,"end":25,"loc":{"start":{"line":2,"column":14},"end":{"line":2,"column":15}},

packages/babel-parser/test/fixtures/es2022/class-private-names-duplicated/static-field-instance-set/output.json

@@ -36,6 +36,7 @@
                   "name": "x"
                 }
               },
+              "accessor": false,
               "value": {
                 "type": "NumericLiteral",
                 "start":24,"end":25,"loc":{"start":{"line":2,"column":14},"end":{"line":2,"column":15}},

packages/babel-parser/test/fixtures/es2022/class-private-names-duplicated/static-field-static-field/output.json

@@ -36,6 +36,7 @@
                   "name": "x"
                 }
               },
+              "accessor": false,
               "value": {
                 "type": "NumericLiteral",
                 "start":24,"end":25,"loc":{"start":{"line":2,"column":14},"end":{"line":2,"column":15}},
@@ -59,6 +60,7 @@
                   "name": "x"
                 }
               },
+              "accessor": false,
               "value": {
                 "type": "NumericLiteral",
                 "start":41,"end":42,"loc":{"start":{"line":3,"column":14},"end":{"line":3,"column":15}},

packages/babel-parser/test/fixtures/es2022/class-private-names-duplicated/static-field-static-get/output.json

@@ -36,6 +36,7 @@
                   "name": "x"
                 }
               },
+              "accessor": false,
               "value": {
                 "type": "NumericLiteral",
                 "start":24,"end":25,"loc":{"start":{"line":2,"column":14},"end":{"line":2,"column":15}},

packages/babel-parser/test/fixtures/es2022/class-private-names-duplicated/static-field-static-method/output.json

@@ -36,6 +36,7 @@
                   "name": "x"
                 }
               },
+              "accessor": false,
               "value": {
                 "type": "NumericLiteral",
                 "start":24,"end":25,"loc":{"start":{"line":2,"column":14},"end":{"line":2,"column":15}},

packages/babel-parser/test/fixtures/es2022/class-private-names-duplicated/static-field-static-set/output.json

@@ -36,6 +36,7 @@
                   "name": "x"
                 }
               },
+              "accessor": false,
               "value": {
                 "type": "NumericLiteral",
                 "start":24,"end":25,"loc":{"start":{"line":2,"column":14},"end":{"line":2,"column":15}},

packages/babel-parser/test/fixtures/es2022/class-private-names-duplicated/static-get-instance-field/output.json

@@ -62,6 +62,7 @@
                   "name": "x"
                 }
               },
+              "accessor": false,
               "value": {
                 "type": "NumericLiteral",
                 "start":38,"end":39,"loc":{"start":{"line":3,"column":7},"end":{"line":3,"column":8}},

packages/babel-parser/test/fixtures/es2022/class-private-names-duplicated/static-get-static-field/output.json

@@ -62,6 +62,7 @@
                   "name": "x"
                 }
               },
+              "accessor": false,
               "value": {
                 "type": "NumericLiteral",
                 "start":45,"end":46,"loc":{"start":{"line":3,"column":14},"end":{"line":3,"column":15}},

packages/babel-parser/test/fixtures/es2022/class-private-names-duplicated/static-method-instance-field/output.json

@@ -61,6 +61,7 @@
                   "name": "x"
                 }
               },
+              "accessor": false,
               "value": {
                 "type": "NumericLiteral",
                 "start":34,"end":35,"loc":{"start":{"line":3,"column":7},"end":{"line":3,"column":8}},

packages/babel-parser/test/fixtures/es2022/class-private-names-duplicated/static-method-static-field/output.json

@@ -61,6 +61,7 @@
                   "name": "x"
                 }
               },
+              "accessor": false,
               "value": {
                 "type": "NumericLiteral",
                 "start":41,"end":42,"loc":{"start":{"line":3,"column":14},"end":{"line":3,"column":15}},

packages/babel-parser/test/fixtures/es2022/class-private-names-duplicated/static-set-instance-field/output.json

@@ -68,6 +68,7 @@
                   "name": "x"
                 }
               },
+              "accessor": false,
               "value": {
                 "type": "NumericLiteral",
                 "start":39,"end":40,"loc":{"start":{"line":3,"column":7},"end":{"line":3,"column":8}},

packages/babel-parser/test/fixtures/es2022/class-private-names-duplicated/static-set-static-field/output.json

@@ -68,6 +68,7 @@
                   "name": "x"
                 }
               },
+              "accessor": false,
               "value": {
                 "type": "NumericLiteral",
                 "start":46,"end":47,"loc":{"start":{"line":3,"column":14},"end":{"line":3,"column":15}},

packages/babel-parser/test/fixtures/es2022/class-private-properties/asi-success/output.json

@@ -48,6 +48,7 @@
                   "name": "y"
                 }
               },
+              "accessor": false,
               "value": null
             }
           ]

packages/babel-parser/test/fixtures/es2022/class-private-properties/await-identifier-in-property-in-arguments-of-async-call/output.json

@@ -50,6 +50,7 @@
                           "name": "x"
                         }
                       },
+                      "accessor": false,
                       "value": {
                         "type": "Identifier",
                         "start":24,"end":29,"loc":{"start":{"line":1,"column":24},"end":{"line":1,"column":29},"identifierName":"await"},