Add the decoratorsAutoAccessors parser plugin

packages/babel-compat-data/data/plugins.json

@@ -379,7 +379,7 @@
     "chrome": "46",
     "opera": "33",
     "edge": "14",
-    "firefox": "45",
+    "firefox": "41",
     "safari": "10",
     "node": "5",
     "ios": "10",

packages/babel-generator/src/generators/classes.ts

@@ -114,6 +114,48 @@ export function ClassProperty(this: Printer, node: t.ClassProperty) {
   this.semicolon();
 }
 
+export function ClassAccessorProperty(
+  this: Printer,
+  node: t.ClassAccessorProperty,
+) {
+  this.printJoin(node.decorators, node);
+
+  // catch up to property key, avoid line break
+  // between member modifiers and the property key.
+  this.source("end", node.key.loc);
+
+  this.tsPrintClassMemberModifiers(node, /* isField */ true);
+
+  this.word("accessor");
+  this.space();
+
+  if (node.computed) {
+    this.token("[");
+    this.print(node.key, node);
+    this.token("]");
+  } else {
+    this._variance(node);
+    this.print(node.key, node);
+  }
+
+  // TS
+  if (node.optional) {
+    this.token("?");
+  }
+  if (node.definite) {
+    this.token("!");
+  }
+
+  this.print(node.typeAnnotation, node);
+  if (node.value) {
+    this.space();
+    this.token("=");
+    this.space();
+    this.print(node.value, node);
+  }
+  this.semicolon();
+}
+
 export function ClassPrivateProperty(
   this: Printer,
   node: t.ClassPrivateProperty,

packages/babel-parser/ast/spec.md

@@ -1213,6 +1213,18 @@ interface ClassPrivateProperty <: Node {
 }
 ```
 
+## ClassAccessorProperty
+
+```js
+interface ClassAccessorProperty <: Node {
+  type: "ClassAccessorProperty";
+  key: Expression | PrivateName;
+  value: Expression;
+  static: boolean;
+  computed: boolean;
+}
+```
+
 ## StaticBlock
 
 ```js

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

@@ -1394,6 +1394,7 @@ export default class StatementParser extends ExpressionParser {
       prop.computed = false;
       prop.key = key;
       prop.static = false;
+
       classBody.body.push(this.parseClassProperty(prop));
       return true;
     }
@@ -1430,8 +1431,9 @@ 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 accessorProp: $FlowSubtype<N.ClassAccessorProperty> = member;
 
     const method: typeof publicMethod | typeof privateMethod = publicMethod;
     const publicMember: typeof publicMethod | typeof publicProp = publicMethod;
@@ -1585,6 +1587,18 @@ export default class StatementParser extends ExpressionParser {
       }
 
       this.checkGetterSetterParams(publicMethod);
+    } else if (
+      isContextual &&
+      key.name === "accessor" &&
+      !this.isLineTerminator()
+    ) {
+      this.expectPlugin("decoratorAutoAccessors");
+      this.resetPreviousNodeTrailingComments(key);
+
+      // The so-called parsed name would have been "accessor": get the real name.
+      const isPrivate = this.match(tt.privateName);
+      this.parseClassElementName(publicProp);
+      this.pushClassAccessorProperty(classBody, accessorProp, isPrivate);
     } else if (this.isLineTerminator()) {
       // an uninitialized class property (due to ASI, since we don't otherwise recognize the next token)
       if (isPrivate) {
@@ -1666,6 +1680,34 @@ export default class StatementParser extends ExpressionParser {
     );
   }
 
+  pushClassAccessorProperty(
+    classBody: N.ClassBody,
+    prop: N.ClassAccessorProperty,
+    isPrivate: boolean,
+  ) {
+    if (!isPrivate && !prop.computed) {
+      // Not private, so not node is not a PrivateName and we can safely cast
+      const key = (prop.key: N.Expression);
+
+      if (key.name === "constructor" || key.value === "constructor") {
+        // Non-computed field, which is either an identifier named "constructor"
+        // or a string literal named "constructor"
+        this.raise(prop.key.start, Errors.ConstructorClassField);
+      }
+    }
+
+    const node = this.parseClassAccessorProperty(prop);
+    classBody.body.push(node);
+
+    if (isPrivate) {
+      this.classScope.declarePrivateName(
+        this.getPrivateNameSV(node.key),
+        CLASS_ELEMENT_OTHER,
+        node.key.start,
+      );
+    }
+  }
+
   pushClassMethod(
     classBody: N.ClassBody,
     method: N.ClassMethod,
@@ -1743,8 +1785,18 @@ export default class StatementParser extends ExpressionParser {
     return this.finishNode(node, "ClassProperty");
   }
 
+  parseClassAccessorProperty(
+    node: N.ClassAccessorProperty,
+  ): N.ClassAccessorProperty {
+    this.parseInitializer(node);
+    this.semicolon();
+    return this.finishNode(node, "ClassAccessorProperty");
+  }
+
   // https://tc39.es/proposal-class-fields/#prod-Initializer
-  parseInitializer(node: N.ClassProperty | N.ClassPrivateProperty): void {
+  parseInitializer(
+    node: N.ClassProperty | N.ClassPrivateProperty | N.ClassAccessorProperty,
+  ): void {
     this.scope.enter(SCOPE_CLASS | SCOPE_SUPER);
     this.expressionScope.enter(newExpressionScope());
     this.prodParam.enter(PARAM);

packages/babel-parser/src/types.js

@@ -782,7 +782,8 @@ export type ClassMember =
   | ClassMethod
   | ClassPrivateMethod
   | ClassProperty
-  | ClassPrivateProperty;
+  | ClassPrivateProperty
+  | ClassAccessorProperty;
 
 export type MethodLike =
   | ObjectMethod
@@ -849,6 +850,20 @@ export type ClassPrivateProperty = NodeBase & {
   override?: true,
 };
 
+export type ClassAccessorProperty = ClassMemberBase &
+  DeclarationBase & {
+    type: "ClassAccessorProperty",
+    key: Expression | PrivateName,
+    value: ?Expression,
+
+    typeAnnotation?: ?TypeAnnotationBase, // TODO: Not in spec
+    variance?: ?FlowVariance, // TODO: Not in spec
+
+    // TypeScript only: (TODO: Not in spec)
+    readonly?: true,
+    definite?: true,
+  };
+
 export type OptClassDeclaration = ClassBase &
   DeclarationBase &
   HasDecorators & {

packages/babel-parser/test/fixtures/experimental/_no-plugin/auto-accessors/input.js

@@ -0,0 +1,3 @@
+class Foo {
+  accessor bar;
+}

packages/babel-parser/test/fixtures/experimental/_no-plugin/auto-accessors/options.json

@@ -0,0 +1,4 @@
+{
+  "throws": "This experimental syntax requires enabling the parser plugin: 'decoratorAutoAccessors' (2:11)",
+  "plugins": []
+}

packages/babel-parser/test/fixtures/experimental/decorator-auto-accessors/accessor-named-constructor/input.js

@@ -0,0 +1,3 @@
+class Foo {
+  accessor constructor;
+}

packages/babel-parser/test/fixtures/experimental/decorator-auto-accessors/accessor-named-constructor/output.json

@@ -0,0 +1,44 @@
+{
+  "type": "File",
+  "start":0,"end":37,"loc":{"start":{"line":1,"column":0},"end":{"line":3,"column":1}},
+  "errors": [
+    "SyntaxError: Classes may not have a field named 'constructor'. (2:11)"
+  ],
+  "program": {
+    "type": "Program",
+    "start":0,"end":37,"loc":{"start":{"line":1,"column":0},"end":{"line":3,"column":1}},
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ClassDeclaration",
+        "start":0,"end":37,"loc":{"start":{"line":1,"column":0},"end":{"line":3,"column":1}},
+        "id": {
+          "type": "Identifier",
+          "start":6,"end":9,"loc":{"start":{"line":1,"column":6},"end":{"line":1,"column":9},"identifierName":"Foo"},
+          "name": "Foo"
+        },
+        "superClass": null,
+        "body": {
+          "type": "ClassBody",
+          "start":10,"end":37,"loc":{"start":{"line":1,"column":10},"end":{"line":3,"column":1}},
+          "body": [
+            {
+              "type": "ClassAccessorProperty",
+              "start":14,"end":35,"loc":{"start":{"line":2,"column":2},"end":{"line":2,"column":23}},
+              "static": false,
+              "key": {
+                "type": "Identifier",
+                "start":23,"end":34,"loc":{"start":{"line":2,"column":11},"end":{"line":2,"column":22},"identifierName":"constructor"},
+                "name": "constructor"
+              },
+              "computed": false,
+              "value": null
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}

packages/babel-parser/test/fixtures/experimental/decorator-auto-accessors/basic-accessor-with-newline/input.js

@@ -0,0 +1,4 @@
+class Foo {
+  accessor
+  bar;
+}

packages/babel-parser/test/fixtures/experimental/decorator-auto-accessors/basic-accessor-with-newline/output.json

@@ -0,0 +1,53 @@
+{
+  "type": "File",
+  "start":0,"end":31,"loc":{"start":{"line":1,"column":0},"end":{"line":4,"column":1}},
+  "program": {
+    "type": "Program",
+    "start":0,"end":31,"loc":{"start":{"line":1,"column":0},"end":{"line":4,"column":1}},
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ClassDeclaration",
+        "start":0,"end":31,"loc":{"start":{"line":1,"column":0},"end":{"line":4,"column":1}},
+        "id": {
+          "type": "Identifier",
+          "start":6,"end":9,"loc":{"start":{"line":1,"column":6},"end":{"line":1,"column":9},"identifierName":"Foo"},
+          "name": "Foo"
+        },
+        "superClass": null,
+        "body": {
+          "type": "ClassBody",
+          "start":10,"end":31,"loc":{"start":{"line":1,"column":10},"end":{"line":4,"column":1}},
+          "body": [
+            {
+              "type": "ClassProperty",
+              "start":14,"end":22,"loc":{"start":{"line":2,"column":2},"end":{"line":2,"column":10}},
+              "static": false,
+              "key": {
+                "type": "Identifier",
+                "start":14,"end":22,"loc":{"start":{"line":2,"column":2},"end":{"line":2,"column":10},"identifierName":"accessor"},
+                "name": "accessor"
+              },
+              "computed": false,
+              "value": null
+            },
+            {
+              "type": "ClassProperty",
+              "start":25,"end":29,"loc":{"start":{"line":3,"column":2},"end":{"line":3,"column":6}},
+              "static": false,
+              "key": {
+                "type": "Identifier",
+                "start":25,"end":28,"loc":{"start":{"line":3,"column":2},"end":{"line":3,"column":5},"identifierName":"bar"},
+                "name": "bar"
+              },
+              "computed": false,
+              "value": null
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}

packages/babel-parser/test/fixtures/experimental/decorator-auto-accessors/basic-accessor/input.js

@@ -0,0 +1,3 @@
+class Foo {
+  accessor bar;
+}

packages/babel-parser/test/fixtures/experimental/decorator-auto-accessors/basic-accessor/output.json

@@ -0,0 +1,41 @@
+{
+  "type": "File",
+  "start":0,"end":29,"loc":{"start":{"line":1,"column":0},"end":{"line":3,"column":1}},
+  "program": {
+    "type": "Program",
+    "start":0,"end":29,"loc":{"start":{"line":1,"column":0},"end":{"line":3,"column":1}},
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ClassDeclaration",
+        "start":0,"end":29,"loc":{"start":{"line":1,"column":0},"end":{"line":3,"column":1}},
+        "id": {
+          "type": "Identifier",
+          "start":6,"end":9,"loc":{"start":{"line":1,"column":6},"end":{"line":1,"column":9},"identifierName":"Foo"},
+          "name": "Foo"
+        },
+        "superClass": null,
+        "body": {
+          "type": "ClassBody",
+          "start":10,"end":29,"loc":{"start":{"line":1,"column":10},"end":{"line":3,"column":1}},
+          "body": [
+            {
+              "type": "ClassAccessorProperty",
+              "start":14,"end":27,"loc":{"start":{"line":2,"column":2},"end":{"line":2,"column":15}},
+              "static": false,
+              "key": {
+                "type": "Identifier",
+                "start":23,"end":26,"loc":{"start":{"line":2,"column":11},"end":{"line":2,"column":14},"identifierName":"bar"},
+                "name": "bar"
+              },
+              "computed": false,
+              "value": null
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}

packages/babel-parser/test/fixtures/experimental/decorator-auto-accessors/computed-accessor-named-constructor/input.js

@@ -0,0 +1,3 @@
+class Foo {
+  accessor ["constructor"];
+}