Adds the simpleAutoAccessors parser plugin

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 adds a `simpleAutoAccessors` plugin which can be used to parse the `accessor` keyword into ClassAccessorProperty and ClassPrivateAccessorProperty node types.
babel · Sep 19, 2021 · 5f6f23e · 5f6f23e
1 parent 3d1481f
commit 5f6f23e
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diff --git a/packages/babel-generator/src/generators/classes.ts b/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,
@@ -134,6 +176,29 @@ export function ClassPrivateProperty(
   this.semicolon();
 }
 
+export function ClassPrivateAccessorProperty(
+  this: Printer,
+  node: t.ClassPrivateAccessorProperty,
+) {
+  this.printJoin(node.decorators, node);
+  if (node.static) {
+    this.word("static");
+    this.space();
+  }
+  this.word("accessor");
+  this.space();
+
+  this.print(node.key, node);
+  this.print(node.typeAnnotation, node);
+  if (node.value) {
+    this.space();
+    this.token("=");
+    this.space();
+    this.print(node.value, node);
+  }
+  this.semicolon();
+}
+
 export function ClassMethod(this: Printer, node: t.ClassMethod) {
   this._classMethodHead(node);
   this.space();

diff --git a/packages/babel-parser/ast/spec.md b/packages/babel-parser/ast/spec.md
@@ -1213,6 +1213,29 @@ interface ClassPrivateProperty <: Node {
 }
 ```
 
+## ClassAccessorProperty
+
+```js
+interface ClassAccessorProperty <: Node {
+  type: "ClassAccessorProperty";
+  key: Expression;
+  value: Expression;
+  static: boolean;
+  computed: boolean;
+}
+```
+
+## ClassPrivateAccessorProperty
+
+```js
+interface ClassPrivateAccessorProperty <: Node {
+  type: "ClassPrivateAccessorProperty";
+  key: PrivateName;
+  value: Expression;
+  static: boolean;
+}
+```
+
 ## StaticBlock
 
 ```js

diff --git a/packages/babel-parser/src/parser/statement.js b/packages/babel-parser/src/parser/statement.js
@@ -1393,6 +1393,7 @@ export default class StatementParser extends ExpressionParser {
       prop.computed = false;
       prop.key = key;
       prop.static = false;
+
       classBody.body.push(this.parseClassProperty(prop));
       return true;
     }
@@ -1429,8 +1430,11 @@ 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 publicAccessorProp: $FlowSubtype<N.ClassAccessorProperty> = member;
+    const privateAccessorProp: $FlowSubtype<N.ClassPrivateAccessorProperty> =
+      member;
 
     const method: typeof publicMethod | typeof privateMethod = publicMethod;
     const publicMember: typeof publicMethod | typeof publicProp = publicMethod;
@@ -1583,6 +1587,23 @@ export default class StatementParser extends ExpressionParser {
       }
 
       this.checkGetterSetterParams(publicMethod);
+    } else if (
+      isContextual &&
+      key.name === "accessor" &&
+      this.hasPlugin("simpleAutoAccessors") &&
+      !this.isLineTerminator()
+    ) {
+      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);
+
+      if (isPrivate) {
+        this.pushClassPrivateAccessorProperty(classBody, privateAccessorProp);
+      } else {
+        this.pushClassAccessorProperty(classBody, publicAccessorProp);
+      }
     } else if (this.isLineTerminator()) {
       // an uninitialized class property (due to ASI, since we don't otherwise recognize the next token)
       if (isPrivate) {
@@ -1664,6 +1685,36 @@ export default class StatementParser extends ExpressionParser {
     );
   }
 
+  pushClassAccessorProperty(
+    classBody: N.ClassBody,
+    prop: N.ClassAccessorProperty,
+  ) {
+    if (
+      !prop.computed &&
+      (prop.key.name === "constructor" || prop.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);
+    }
+
+    classBody.body.push(this.parseClassAccessorProperty(prop));
+  }
+
+  pushClassPrivateAccessorProperty(
+    classBody: N.ClassBody,
+    prop: N.ClassPrivateAccessorProperty,
+  ) {
+    const node = this.parseClassPrivateAccessorProperty(prop);
+    classBody.body.push(node);
+
+    this.classScope.declarePrivateName(
+      this.getPrivateNameSV(node.key),
+      CLASS_ELEMENT_OTHER,
+      node.key.start,
+    );
+  }
+
   pushClassMethod(
     classBody: N.ClassBody,
     method: N.ClassMethod,
@@ -1741,6 +1792,22 @@ export default class StatementParser extends ExpressionParser {
     return this.finishNode(node, "ClassProperty");
   }
 
+  parseClassPrivateAccessorProperty(
+    node: N.ClassPrivateAccessorProperty,
+  ): N.ClassPrivateAccessorProperty {
+    this.parseInitializer(node);
+    this.semicolon();
+    return this.finishNode(node, "ClassPrivateAccessorProperty");
+  }
+
+  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 {
     this.scope.enter(SCOPE_CLASS | SCOPE_SUPER);

diff --git a/packages/babel-parser/src/types.js b/packages/babel-parser/src/types.js
@@ -849,6 +849,37 @@ export type ClassPrivateProperty = NodeBase & {
   override?: true,
 };
 
+export type ClassAccessorProperty = ClassMemberBase &
+  DeclarationBase & {
+    type: "ClassAccesorProperty",
+    key: Expression,
+    init?: Expression, // TODO: Not in spec that this is nullable.
+
+    typeAnnotation?: ?TypeAnnotationBase, // TODO: Not in spec
+    variance?: ?FlowVariance, // TODO: Not in spec
+
+    // TypeScript only: (TODO: Not in spec)
+    readonly?: true,
+    definite?: true,
+  };
+
+export type ClassPrivateAccessorProperty = NodeBase & {
+  type: "ClassPrivateAccessorProperty",
+  key: PrivateName,
+  init?: Expression, // TODO: Not in spec that this is nullable.
+  static: boolean,
+  computed: false,
+
+  // Flow and Typescript
+  typeAnnotation?: ?TypeAnnotationBase,
+
+  // TypeScript only
+  optional?: true,
+  definite?: true,
+  readonly?: true,
+  override?: true,
+};
+
 export type OptClassDeclaration = ClassBase &
   DeclarationBase &
   HasDecorators & {

diff --git a/...rser/test/fixtures/experimental/simple-auto-accessors/accessor-named-constructor/input.js b/...rser/test/fixtures/experimental/simple-auto-accessors/accessor-named-constructor/input.js
@@ -0,0 +1,3 @@
+class Foo {
+  accessor constructor;
+}
diff --git a/...r/test/fixtures/experimental/simple-auto-accessors/accessor-named-constructor/output.json b/...r/test/fixtures/experimental/simple-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": []
+  }
+}
diff --git a/...ser/test/fixtures/experimental/simple-auto-accessors/basic-accessor-with-newline/input.js b/...ser/test/fixtures/experimental/simple-auto-accessors/basic-accessor-with-newline/input.js
@@ -0,0 +1,4 @@
+class Foo {
+  accessor
+  bar;
+}
diff --git a/.../test/fixtures/experimental/simple-auto-accessors/basic-accessor-with-newline/output.json b/.../test/fixtures/experimental/simple-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": []
+  }
+}
diff --git a/...ges/babel-parser/test/fixtures/experimental/simple-auto-accessors/basic-accessor/input.js b/...ges/babel-parser/test/fixtures/experimental/simple-auto-accessors/basic-accessor/input.js
@@ -0,0 +1,3 @@
+class Foo {
+  accessor bar;
+}