Parse class static block

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

@@ -134,3 +134,18 @@ export function _classMethodHead(node) {
   this.tsPrintClassMemberModifiers(node, /* isField */ false);
   this._methodHead(node);
 }
+
+export function StaticBlock(node) {
+  this.word("static");
+  this.space();
+  this.token("{");
+  if (node.body.length === 0) {
+    this.token("}");
+  } else {
+    this.newline();
+    this.printSequence(node.body, node, {
+      indent: true,
+    });
+    this.rightBrace();
+  }
+}

packages/babel-generator/test/fixtures/minified/static-block/input.js

@@ -0,0 +1,16 @@
+class Foo {
+  static {}
+}
+
+class A1 {
+  static{
+    foo;
+  }
+}
+
+class A2 {
+  static {
+    foo;
+    bar;
+  }
+}

packages/babel-generator/test/fixtures/minified/static-block/options.json

@@ -0,0 +1,4 @@
+{
+  "minified": true,
+  "plugins": ["classStaticBlock"]
+}

packages/babel-generator/test/fixtures/minified/static-block/output.js

@@ -0,0 +1 @@
+class Foo{static{}}class A1{static{foo}}class A2{static{foo;bar}}

packages/babel-generator/test/fixtures/types/ClassBody-StaticBlock/input.js

@@ -0,0 +1,15 @@
+class Foo {
+  static {}
+}
+
+class A1 {
+  static{
+    foo;
+  }
+}
+
+class A2 {
+  static {
+    foo;bar;
+  }
+}

packages/babel-generator/test/fixtures/types/ClassBody-StaticBlock/options.json

@@ -0,0 +1 @@
+{ "plugins": ["classStaticBlock"] }

packages/babel-generator/test/fixtures/types/ClassBody-StaticBlock/output.js

@@ -0,0 +1,16 @@
+class Foo {
+  static {}
+}
+
+class A1 {
+  static {
+    foo;
+  }
+}
+
+class A2 {
+  static {
+    foo;
+    bar;
+  }
+}

packages/babel-parser/ast/spec.md

@@ -1183,7 +1183,7 @@ interface Class <: Node {
 ```js
 interface ClassBody <: Node {
   type: "ClassBody";
-  body: [ ClassMethod | ClassPrivateMethod | ClassProperty | ClassPrivateProperty ];
+  body: [ ClassMethod | ClassPrivateMethod | ClassProperty | ClassPrivateProperty | StaticBlock ];
 }
 ```
 
@@ -1235,6 +1235,17 @@ interface ClassPrivateProperty <: Node {
 }
 ```
 
+## StaticBlock
+
+```js
+interface StaticBlock <: Node {
+  type: "StaticBlock";
+  body: [ Statement ];
+}
+```
+
+A static block proposed in https://github.com/tc39/proposal-class-static-block.
+
 ## ClassDeclaration
 
 ```js

packages/babel-parser/src/parser/error-message.js

@@ -4,8 +4,8 @@
 // The Errors key follows https://cs.chromium.org/chromium/src/v8/src/common/message-template.h unless it does not exist
 export const ErrorMessages = Object.freeze({
   AccessorIsGenerator: "A %0ter cannot be a generator",
-  ArgumentsDisallowedInInitializer:
-    "'arguments' is not allowed in class field initializer",
+  ArgumentsInClass:
+    "'arguments' is only allowed in functions and class methods",
   AsyncFunctionInSingleStatementContext:
     "Async functions can only be declared at the top level or inside a block",
   AwaitBindingIdentifier:
@@ -32,6 +32,7 @@ export const ErrorMessages = Object.freeze({
   DecoratorExportClass:
     "Using the export keyword between a decorator and a class is not allowed. Please use `export @dec class` instead.",
   DecoratorSemicolon: "Decorators must not be followed by a semicolon",
+  DecoratorStaticBlock: "Decorators can't be used with a static block",
   DeletePrivateField: "Deleting a private field is not allowed",
   DestructureNamedImport:
     "ES2015 named imports do not destructure. Use another statement for destructuring after the import.",
@@ -41,6 +42,7 @@ export const ErrorMessages = Object.freeze({
     "`%0` has already been exported. Exported identifiers must be unique.",
   DuplicateProto: "Redefinition of __proto__ property",
   DuplicateRegExpFlags: "Duplicate regular expression flag",
+  DuplicateStaticBlock: "Duplicate static block in the same class",
   ElementAfterRest: "Rest element must be last element",
   EscapedCharNotAnIdentifier: "Invalid Unicode escape",
   ExportDefaultFromAsIdentifier:

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

@@ -2382,7 +2382,7 @@ export default class ExpressionParser extends LValParser {
       !this.scope.inNonArrowFunction &&
       word === "arguments"
     ) {
-      this.raise(startLoc, Errors.ArgumentsDisallowedInInitializer);
+      this.raise(startLoc, Errors.ArgumentsInClass);
       return;
     }
     if (checkKeywords && isKeyword(word)) {

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

@@ -795,7 +795,7 @@ export default class StatementParser extends ExpressionParser {
   }
 
   // Parse a semicolon-enclosed block of statements, handling `"use
-  // strict"` declarations when `allowStrict` is true (used for
+  // strict"` declarations when `allowDirectives` is true (used for
   // function bodies).
 
   parseBlock(
@@ -1205,7 +1205,11 @@ export default class StatementParser extends ExpressionParser {
   ): N.ClassBody {
     this.classScope.enter();
 
-    const state = { hadConstructor: false };
+    const state: N.ParseClassMemberState = {
+      constructorAllowsSuper,
+      hadConstructor: false,
+      hadStaticBlock: false,
+    };
     let decorators: N.Decorator[] = [];
     const classBody: N.ClassBody = this.startNode();
     classBody.body = [];
@@ -1237,7 +1241,7 @@ export default class StatementParser extends ExpressionParser {
           decorators = [];
         }
 
-        this.parseClassMember(classBody, member, state, constructorAllowsSuper);
+        this.parseClassMember(classBody, member, state);
 
         if (
           member.kind === "constructor" &&
@@ -1303,31 +1307,33 @@ export default class StatementParser extends ExpressionParser {
   parseClassMember(
     classBody: N.ClassBody,
     member: N.ClassMember,
-    state: { hadConstructor: boolean },
-    constructorAllowsSuper: boolean,
+    state: N.ParseClassMemberState,
   ): void {
     const isStatic = this.isContextual("static");
 
-    if (isStatic && this.parseClassMemberFromModifier(classBody, member)) {
-      // a class element named 'static'
-      return;
+    if (isStatic) {
+      if (this.parseClassMemberFromModifier(classBody, member)) {
+        // a class element named 'static'
+        return;
+      }
+      if (this.eat(tt.braceL)) {
+        this.parseClassStaticBlock(
+          classBody,
+          ((member: any): N.StaticBlock),
+          state,
+        );
+        return;
+      }
     }
 
-    this.parseClassMemberWithIsStatic(
-      classBody,
-      member,
-      state,
-      isStatic,
-      constructorAllowsSuper,
-    );
+    this.parseClassMemberWithIsStatic(classBody, member, state, isStatic);
   }
 
   parseClassMemberWithIsStatic(
     classBody: N.ClassBody,
     member: N.ClassMember,
-    state: { hadConstructor: boolean },
+    state: N.ParseClassMemberState,
     isStatic: boolean,
-    constructorAllowsSuper: boolean,
   ) {
     const publicMethod: $FlowSubtype<N.ClassMethod> = member;
     const privateMethod: $FlowSubtype<N.ClassPrivateMethod> = member;
@@ -1394,7 +1400,7 @@ export default class StatementParser extends ExpressionParser {
           this.raise(key.start, Errors.DuplicateConstructor);
         }
         state.hadConstructor = true;
-        allowsDirectSuper = constructorAllowsSuper;
+        allowsDirectSuper = state.constructorAllowsSuper;
       }
 
       this.pushClassMethod(
@@ -1513,6 +1519,35 @@ export default class StatementParser extends ExpressionParser {
     return key;
   }
 
+  parseClassStaticBlock(
+    classBody: N.ClassBody,
+    member: N.StaticBlock & { decorators?: Array<N.Decorator> },
+    state: N.ParseClassMemberState,
+  ) {
+    this.expectPlugin("classStaticBlock", member.start);
+    // Start a new lexical scope
+    this.scope.enter(SCOPE_CLASS | SCOPE_SUPER);
+    // Start a new scope with regard to loop labels
+    const oldLabels = this.state.labels;
+    this.state.labels = [];
+    // ClassStaticBlockStatementList:
+    //   StatementList[~Yield, ~Await, ~Return] opt
+    this.prodParam.enter(PARAM);
+    const body = (member.body = []);
+    this.parseBlockOrModuleBlockBody(body, undefined, false, tt.braceR);
+    this.prodParam.exit();
+    this.scope.exit();
+    this.state.labels = oldLabels;
+    classBody.body.push(this.finishNode<N.StaticBlock>(member, "StaticBlock"));
+    if (state.hadStaticBlock) {
+      this.raise(member.start, Errors.DuplicateStaticBlock);
+    }
+    if (member.decorators?.length) {
+      this.raise(member.start, Errors.DecoratorStaticBlock);
+    }
+    state.hadStaticBlock = true;
+  }
+
   pushClassProperty(classBody: N.ClassBody, prop: N.ClassProperty) {
     if (
       !prop.computed &&

packages/babel-parser/src/plugins/flow.js

@@ -2096,8 +2096,7 @@ export default (superClass: Class<Parser>): Class<Parser> =>
     parseClassMember(
       classBody: N.ClassBody,
       member: any,
-      state: { hadConstructor: boolean },
-      constructorAllowsSuper: boolean,
+      state: N.ParseClassMemberState,
     ): void {
       const pos = this.state.start;
       if (this.isContextual("declare")) {
@@ -2109,7 +2108,7 @@ export default (superClass: Class<Parser>): Class<Parser> =>
         member.declare = true;
       }
 
-      super.parseClassMember(classBody, member, state, constructorAllowsSuper);
+      super.parseClassMember(classBody, member, state);
 
       if (member.declare) {
         if (

packages/babel-parser/src/plugins/typescript/index.js

@@ -2068,21 +2068,15 @@ export default (superClass: Class<Parser>): Class<Parser> =>
     parseClassMember(
       classBody: N.ClassBody,
       member: any,
-      state: { hadConstructor: boolean },
-      constructorAllowsSuper: boolean,
+      state: N.ParseClassMemberState,
     ): void {
       this.tsParseModifiers(member, ["declare"]);
       const accessibility = this.parseAccessModifier();
       if (accessibility) member.accessibility = accessibility;
       this.tsParseModifiers(member, ["declare"]);
 
       const callParseClassMember = () => {
-        super.parseClassMember(
-          classBody,
-          member,
-          state,
-          constructorAllowsSuper,
-        );
+        super.parseClassMember(classBody, member, state);
       };
       if (member.declare) {
         this.tsInDeclareContext(callParseClassMember);
@@ -2094,9 +2088,8 @@ export default (superClass: Class<Parser>): Class<Parser> =>
     parseClassMemberWithIsStatic(
       classBody: N.ClassBody,
       member: N.ClassMember | N.TsIndexSignature,
-      state: { hadConstructor: boolean },
+      state: N.ParseClassMemberState,
       isStatic: boolean,
-      constructorAllowsSuper: boolean,
     ): void {
       this.tsParseModifiers(member, ["abstract", "readonly", "declare"]);
 
@@ -2126,13 +2119,7 @@ export default (superClass: Class<Parser>): Class<Parser> =>
 
       /*:: invariant(member.type !== "TSIndexSignature") */
 
-      super.parseClassMemberWithIsStatic(
-        classBody,
-        member,
-        state,
-        isStatic,
-        constructorAllowsSuper,
-      );
+      super.parseClassMemberWithIsStatic(classBody, member, state, isStatic);
     }
 
     parsePostMemberNameModifiers(

packages/babel-parser/src/types.js

@@ -705,7 +705,7 @@ export type ClassBase = HasDecorators & {
 
 export type ClassBody = NodeBase & {
   type: "ClassBody",
-  body: Array<ClassMember | TsIndexSignature>, // TODO: $ReadOnlyArray
+  body: Array<ClassMember | StaticBlock | TsIndexSignature>, // TODO: $ReadOnlyArray
 };
 // | Placeholder<"ClassBody">;
 
@@ -719,6 +719,11 @@ export type ClassMemberBase = NodeBase &
     optional?: ?true,
   };
 
+export type StaticBlock = NodeBase & {
+  type: "StaticBlock",
+  body: Array<Statement>,
+};
+
 export type ClassMember =
   | ClassMethod
   | ClassPrivateMethod
@@ -1487,3 +1492,9 @@ export type ParseSubscriptState = {
   maybeAsyncArrow: boolean,
   stop: boolean,
 };
+
+export type ParseClassMemberState = {|
+  hadConstructor: boolean,
+  hadStaticBlock: boolean,
+  constructorAllowsSuper: boolean,
+|};

packages/babel-parser/test/fixtures/experimental/_no-plugin/class-static-block/input.js

@@ -0,0 +1,6 @@
+class C {
+  static foo() {}
+  static {
+    this.bar = this.foo;
+  }
+}

packages/babel-parser/test/fixtures/experimental/_no-plugin/class-static-block/options.json

@@ -0,0 +1,3 @@
+{
+  "throws": "This experimental syntax requires enabling the parser plugin: 'classStaticBlock' (3:2)"
+}

packages/babel-parser/test/fixtures/experimental/class-properties/arguments-in-arrow-function/output.json

@@ -2,7 +2,7 @@
   "type": "File",
   "start":0,"end":60,"loc":{"start":{"line":1,"column":0},"end":{"line":5,"column":1}},
   "errors": [
-    "SyntaxError: 'arguments' is not allowed in class field initializer (3:16)"
+    "SyntaxError: 'arguments' is only allowed in functions and class methods (3:16)"
   ],
   "program": {
     "type": "Program",

packages/babel-parser/test/fixtures/experimental/class-properties/arguments-in-nested-class-decorator-call-expression/output.json

@@ -2,7 +2,7 @@
   "type": "File",
   "start":0,"end":76,"loc":{"start":{"line":1,"column":0},"end":{"line":5,"column":1}},
   "errors": [
-    "SyntaxError: 'arguments' is not allowed in class field initializer (3:25)"
+    "SyntaxError: 'arguments' is only allowed in functions and class methods (3:25)"
   ],
   "program": {
     "type": "Program",