Compile static blocks without the intermediate priv field step

packages/babel-helper-create-class-features-plugin/src/features.js

@@ -6,6 +6,7 @@ export const FEATURES = Object.freeze({
   privateMethods: 1 << 2,
   decorators: 1 << 3,
   privateIn: 1 << 4,
+  staticBlocks: 1 << 5,
 });
 
 const featuresSameLoose = new Map([
@@ -144,8 +145,8 @@ export function verifyUsedFeatures(path, file) {
     }
   }
 
-  // NOTE: We can't use path.isPrivateMethod() because it isn't supported in <7.2.0
-  if (path.isPrivate() && path.isMethod()) {
+  // NOTE: path.isPrivateMethod() it isn't supported in <7.2.0
+  if (path.isPrivateMethod?.()) {
     if (!hasFeature(file, FEATURES.privateMethods)) {
       throw path.buildCodeFrameError("Class private methods are not enabled.");
     }
@@ -170,4 +171,13 @@ export function verifyUsedFeatures(path, file) {
       throw path.buildCodeFrameError("Class fields are not enabled.");
     }
   }
+
+  if (path.isStaticBlock?.()) {
+    if (!hasFeature(file, FEATURES.staticBlocks)) {
+      throw path.buildCodeFrameError(
+        "Static class blocks are not enabled. " +
+          "Please add `@babel/plugin-proposal-class-static-block` to your configuration.",
+      );
+    }
+  }
 }

packages/babel-helper-create-class-features-plugin/src/fields.js

@@ -669,7 +669,14 @@ const thisContextVisitor = traverse.visitors.merge([
   environmentVisitor,
 ]);
 
-function replaceThisContext(path, ref, superRef, file, constantSuper) {
+function replaceThisContext(
+  path,
+  ref,
+  superRef,
+  file,
+  isStaticBlock,
+  constantSuper,
+) {
   const state = { classRef: ref, needsClassRef: false };
 
   const replacer = new ReplaceSupers({
@@ -680,13 +687,13 @@ function replaceThisContext(path, ref, superRef, file, constantSuper) {
     refToPreserve: ref,
     getObjectRef() {
       state.needsClassRef = true;
-      return path.node.static
+      return isStaticBlock || path.node.static
         ? ref
         : t.memberExpression(ref, t.identifier("prototype"));
     },
   });
   replacer.replace();
-  if (path.isProperty()) {
+  if (isStaticBlock || path.isProperty()) {
     path.traverse(thisContextVisitor, state);
   }
   return state.needsClassRef;
@@ -717,19 +724,26 @@ export function buildFieldsInitNodes(
     const isPublic = !isPrivate;
     const isField = prop.isProperty();
     const isMethod = !isField;
+    const isStaticBlock = prop.isStaticBlock?.();
 
-    if (isStatic || (isMethod && isPrivate)) {
+    if (isStatic || (isMethod && isPrivate) || isStaticBlock) {
       const replaced = replaceThisContext(
         prop,
         ref,
         superRef,
         state,
+        isStaticBlock,
         constantSuper,
       );
       needsClassRef = needsClassRef || replaced;
     }
 
     switch (true) {
+      case isStaticBlock:
+        staticNodes.push(
+          template.statement.ast`(() => ${t.blockStatement(prop.node.body)})()`,
+        );
+        break;
       case isStatic && isPrivate && isField && privateFieldsAsProperties:
         needsClassRef = true;
         staticNodes.push(

packages/babel-helper-create-class-features-plugin/src/index.js

@@ -146,24 +146,16 @@ export function createClassFeaturePlugin({
             constructor = path;
           } else {
             elements.push(path);
-            if (path.isProperty() || path.isPrivate()) {
+            if (
+              path.isProperty() ||
+              path.isPrivate() ||
+              path.isStaticBlock?.()
+            ) {
               props.push(path);
             }
           }
 
           if (!isDecorated) isDecorated = hasOwnDecorators(path.node);
-
-          if (path.isStaticBlock?.()) {
-            throw path.buildCodeFrameError(`Incorrect plugin order, \`@babel/plugin-proposal-class-static-block\` should be placed before class features plugins
-{
-  "plugins": [
-    "@babel/plugin-proposal-class-static-block",
-    "@babel/plugin-proposal-private-property-in-object",
-    "@babel/plugin-proposal-private-methods",
-    "@babel/plugin-proposal-class-properties",
-  ]
-}`);
-          }
         }
 
         if (!props.length && !isDecorated) return;

packages/babel-helper-create-class-features-plugin/test/fixtures/missing-class-static-blocks-plugin/basic/input.js

@@ -0,0 +1,4 @@
+class A {
+  #x;
+  static {}
+}

packages/babel-helper-create-class-features-plugin/test/fixtures/missing-class-static-blocks-plugin/basic/options.json

@@ -0,0 +1,4 @@
+{
+  "plugins": ["proposal-class-properties", "syntax-class-static-block"],
+  "throws": "Static class blocks are not enabled. Please add `@babel/plugin-proposal-class-static-block` to your configuration."
+}

packages/babel-helper-replace-supers/src/index.ts

@@ -281,7 +281,8 @@ export default class ReplaceSupers {
     this.methodPath = path;
     this.isDerivedConstructor =
       path.isClassMethod({ kind: "constructor" }) && !!opts.superRef;
-    this.isStatic = path.isObjectMethod() || path.node.static;
+    this.isStatic =
+      path.isObjectMethod() || path.node.static || path.isStaticBlock?.();
     this.isPrivateMethod = path.isPrivate() && path.isMethod();
 
     this.file = opts.file;

packages/babel-plugin-proposal-class-static-block/package.json

@@ -19,6 +19,7 @@
     "babel-plugin"
   ],
   "dependencies": {
+    "@babel/helper-create-class-features-plugin": "workspace:^7.13.11",
     "@babel/helper-plugin-utils": "workspace:^7.13.0",
     "@babel/plugin-syntax-class-static-block": "workspace:^7.12.13"
   },

packages/babel-plugin-proposal-class-static-block/src/index.js

@@ -1,6 +1,11 @@
 import { declare } from "@babel/helper-plugin-utils";
 import syntaxClassStaticBlock from "@babel/plugin-syntax-class-static-block";
 
+import {
+  enableFeature,
+  FEATURES,
+} from "@babel/helper-create-class-features-plugin";
+
 /**
  * Generate a uid that is not in `denyList`
  *
@@ -25,10 +30,19 @@ export default declare(({ types: t, template, assertVersion }) => {
   return {
     name: "proposal-class-static-block",
     inherits: syntaxClassStaticBlock,
+
+    pre() {
+      // Enable this in @babel/helper-create-class-features-plugin, so that it
+      // can be handled by the private fields and methods transform.
+      enableFeature(this.file, FEATURES.staticBlocks, /* loose */ false);
+    },
+
     visitor: {
-      Class(path: NodePath<Class>) {
-        const { scope } = path;
-        const classBody = path.get("body");
+      // Run on ClassBody and not on class so that if @babel/helper-create-class-features-plugin
+      // is enabled it can generte optimized output without passing from the intermediate
+      // private fields representation.
+      ClassBody(classBody: NodePath<Class>) {
+        const { scope } = classBody;
         const privateNames = new Set();
         const body = classBody.get("body");
         for (const path of body) {

packages/babel-plugin-proposal-class-static-block/test/fixtures/integration-loose/class-binding/output.js

@@ -1,12 +1,9 @@
-var _ = /*#__PURE__*/babelHelpers.classPrivateFieldLooseKey("_");
-
 class Foo {}
 
 Foo.bar = 42;
-Object.defineProperty(Foo, _, {
-  writable: true,
-  value: (() => {
-    Foo.foo = Foo.bar;
-  })()
-});
+
+(() => {
+  Foo.foo = Foo.bar;
+})();
+
 expect(Foo.foo).toBe(42);

packages/babel-plugin-proposal-class-static-block/test/fixtures/integration-loose/class-declaration/output.js

@@ -1,12 +1,9 @@
-var _ = /*#__PURE__*/babelHelpers.classPrivateFieldLooseKey("_");
-
 class Foo {}
 
 Foo.bar = 42;
-Object.defineProperty(Foo, _, {
-  writable: true,
-  value: (() => {
-    Foo.foo = Foo.bar;
-  })()
-});
+
+(() => {
+  Foo.foo = Foo.bar;
+})();
+
 expect(Foo.foo).toBe(42);

packages/babel-plugin-proposal-class-static-block/test/fixtures/integration-loose/in-class-heritage/output.js

@@ -1,23 +1,13 @@
-var _class, _2, _temp, _class2, _3, _temp2;
+var _class, _temp, _class2, _temp2;
 
-var _ = /*#__PURE__*/babelHelpers.classPrivateFieldLooseKey("_");
+class Foo extends (_temp = _class = class extends (_temp2 = _class2 = class Base {}, (() => {
+  _class2.qux = 21;
+})(), _temp2) {}, (() => {
+  _class.bar = 21;
+})(), _temp) {}
 
-class Foo extends (_temp = (_2 = /*#__PURE__*/babelHelpers.classPrivateFieldLooseKey("_"), _class = class extends (_temp2 = (_3 = /*#__PURE__*/babelHelpers.classPrivateFieldLooseKey("_"), _class2 = class Base {}), Object.defineProperty(_class2, _3, {
-  writable: true,
-  value: (() => {
-    _class2.qux = 21;
-  })()
-}), _temp2) {}), Object.defineProperty(_class, _2, {
-  writable: true,
-  value: (() => {
-    _class.bar = 21;
-  })()
-}), _temp) {}
+(() => {
+  Foo.foo = Foo.bar + Foo.qux;
+})();
 
-Object.defineProperty(Foo, _, {
-  writable: true,
-  value: (() => {
-    Foo.foo = Foo.bar + Foo.qux;
-  })()
-});
 expect(Foo.foo).toBe(42);

packages/babel-plugin-proposal-class-static-block/test/fixtures/integration-loose/multiple-static-initializers/output.js

@@ -1,26 +1,19 @@
 var _bar = /*#__PURE__*/babelHelpers.classPrivateFieldLooseKey("bar");
 
-var _ = /*#__PURE__*/babelHelpers.classPrivateFieldLooseKey("_");
-
-var _2 = /*#__PURE__*/babelHelpers.classPrivateFieldLooseKey("_2");
-
 class Foo {}
 
 Object.defineProperty(Foo, _bar, {
   writable: true,
   value: 21
 });
-Object.defineProperty(Foo, _, {
-  writable: true,
-  value: (() => {
-    Foo.foo = babelHelpers.classPrivateFieldLooseBase(Foo, _bar)[_bar];
-    Foo.qux1 = Foo.qux;
-  })()
-});
+
+(() => {
+  Foo.foo = babelHelpers.classPrivateFieldLooseBase(Foo, _bar)[_bar];
+  Foo.qux1 = Foo.qux;
+})();
+
 Foo.qux = 21;
-Object.defineProperty(Foo, _2, {
-  writable: true,
-  value: (() => {
-    Foo.qux2 = Foo.qux;
-  })()
-});
+
+(() => {
+  Foo.qux2 = Foo.qux;
+})();

packages/babel-plugin-proposal-class-static-block/test/fixtures/integration-loose/name-conflict/output.js

@@ -1,17 +1,14 @@
 var _ = /*#__PURE__*/babelHelpers.classPrivateFieldLooseKey("_");
 
-var _2 = /*#__PURE__*/babelHelpers.classPrivateFieldLooseKey("_2");
-
 class Foo {}
 
 Object.defineProperty(Foo, _, {
   writable: true,
   value: 42
 });
-Object.defineProperty(Foo, _2, {
-  writable: true,
-  value: (() => {
-    Foo.foo = babelHelpers.classPrivateFieldLooseBase(Foo, _)[_];
-  })()
-});
+
+(() => {
+  Foo.foo = babelHelpers.classPrivateFieldLooseBase(Foo, _)[_];
+})();
+
 expect(Foo.foo).toBe(42);

packages/babel-plugin-proposal-class-static-block/test/fixtures/integration-loose/super-static-block/output.js

@@ -1,26 +1,17 @@
-var _class, _2, _temp;
+var _class, _temp;
 
-var _ = /*#__PURE__*/babelHelpers.classPrivateFieldLooseKey("_");
-
-class Foo extends (_temp = (_2 = /*#__PURE__*/babelHelpers.classPrivateFieldLooseKey("_"), _class = class {}), Object.defineProperty(_class, _2, {
-  writable: true,
-  value: (() => {
-    _class.bar = 42;
-  })()
-}), _temp) {}
+class Foo extends (_temp = _class = class {}, (() => {
+  _class.bar = 42;
+})(), _temp) {}
 
 Foo.bar = 21;
-Object.defineProperty(Foo, _, {
-  writable: true,
-  value: (() => {
-    var _class2, _3, _temp2;
 
-    Foo.foo = (_temp2 = (_3 = /*#__PURE__*/babelHelpers.classPrivateFieldLooseKey("_"), _class2 = class {}), Object.defineProperty(_class2, _3, {
-      writable: true,
-      value: (() => {
-        _class2.bar = 42;
-      })()
-    }), _temp2).bar;
-  })()
-});
+(() => {
+  var _class2, _temp2;
+
+  Foo.foo = (_temp2 = _class2 = class {}, (() => {
+    _class2.bar = 42;
+  })(), _temp2).bar;
+})();
+
 expect(Foo.foo).toBe(42);

packages/babel-plugin-proposal-class-static-block/test/fixtures/integration/class-binding/output.js

@@ -1,10 +1,9 @@
 class Foo {}
 
 babelHelpers.defineProperty(Foo, "bar", 42);
-var _ = {
-  writable: true,
-  value: (() => {
-    Foo.foo = Foo.bar;
-  })()
-};
+
+(() => {
+  Foo.foo = Foo.bar;
+})();
+
 expect(Foo.foo).toBe(42);

packages/babel-plugin-proposal-class-static-block/test/fixtures/integration/class-declaration/output.js

@@ -1,10 +1,9 @@
 class Foo {}
 
 babelHelpers.defineProperty(Foo, "bar", 42);
-var _ = {
-  writable: true,
-  value: (() => {
-    Foo.foo = Foo.bar;
-  })()
-};
+
+(() => {
+  Foo.foo = Foo.bar;
+})();
+
 expect(Foo.foo).toBe(42);