Allow compiling #foo in obj without compiling private fields

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

@@ -20,7 +20,7 @@ import {
   isLoose,
 } from "./features";
 
-export { FEATURES, injectInitialization };
+export { FEATURES, enableFeature, injectInitialization };
 
 // Note: Versions are represented as an integer. e.g. 7.1.5 is represented
 //       as 70000100005. This method is easier than using a semver-parsing

packages/babel-plugin-proposal-private-property-in-object/package.json

@@ -17,8 +17,10 @@
     "babel-plugin"
   ],
   "dependencies": {
+    "@babel/helper-compilation-targets": "workspace:^7.12.17",
     "@babel/helper-create-class-features-plugin": "workspace:^7.13.0",
-    "@babel/helper-plugin-utils": "workspace:^7.13.0"
+    "@babel/helper-plugin-utils": "workspace:^7.13.0",
+    "@babel/plugin-syntax-private-property-in-object": "workspace:^7.13.0"
   },
   "peerDependencies": {
     "@babel/core": "^7.0.0-0"

packages/babel-plugin-proposal-private-property-in-object/src/index.js

@@ -1,23 +1,158 @@
-/* eslint-disable @babel/development/plugin-name */
-
 import { declare } from "@babel/helper-plugin-utils";
+import syntaxPlugin from "@babel/plugin-syntax-private-property-in-object";
 import {
-  createClassFeaturePlugin,
+  enableFeature,
   FEATURES,
+  injectInitialization as injectConstructorInit,
 } from "@babel/helper-create-class-features-plugin";
 
-export default declare((api, options) => {
-  api.assertVersion(7);
+export default declare(({ assertVersion, types: t, template }, { loose }) => {
+  assertVersion(7);
+
+  // NOTE: When using the class fields or private methods plugins,
+  // they will also take care of '#priv in obj' checks when visiting
+  // the ClassExpression or ClassDeclaration nodes.
+  // The visitor of this plugin is only effective when not compiling
+  // private fields and methods.
+
+  const classWeakSets = new WeakMap();
+  const fieldsWeakSets = new WeakMap();
+
+  function unshadow(name, targetScope, scope) {
+    while (scope !== targetScope) {
+      if (scope.hasOwnBinding(name)) scope.rename(name);
+      scope = scope.parent;
+    }
+  }
+
+  function injectToFieldInit(fieldPath, expr, before = false) {
+    if (fieldPath.node.value) {
+      if (before) {
+        fieldPath.get("value").insertBefore(expr);
+      } else {
+        fieldPath.get("value").insertAfter(expr);
+      }
+    } else {
+      fieldPath.set("value", t.unaryExpression("void", expr));
+    }
+  }
+
+  function injectInitialization(classPath, init) {
+    let firstFieldPath;
+    let consturctorPath;
+
+    for (const el of classPath.get("body.body")) {
+      if (
+        (el.isClassProperty() || el.isClassPrivateProperty()) &&
+        !el.node.static
+      ) {
+        firstFieldPath = el;
+        break;
+      }
+      if (!consturctorPath && el.isClassMethod({ kind: "constructor" })) {
+        consturctorPath = el;
+      }
+    }
+
+    if (firstFieldPath) {
+      injectToFieldInit(firstFieldPath, init, true);
+    } else {
+      injectConstructorInit(classPath, consturctorPath, [
+        t.expressionStatement(init),
+      ]);
+    }
+  }
+
+  function getWeakSetId(weakSets, outerClass, reference, name = "", inject) {
+    let id = classWeakSets.get(reference.node);
+
+    if (!id) {
+      id = outerClass.scope.generateUidIdentifier(`${name || ""} brandCheck`);
+      classWeakSets.set(reference.node, id);
+
+      inject(reference, template.expression.ast`${t.cloneNode(id)}.add(this)`);
+
+      outerClass.insertBefore(template.ast`var ${id} = new WeakSet()`);
+    }
+
+    return t.cloneNode(id);
+  }
+
+  return {
+    name: "proposal-private-property-in-object",
+    inherits: syntaxPlugin,
+    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.privateIn, loose);
+    },
+    visitor: {
+      BinaryExpression(path) {
+        const { node } = path;
+        if (node.operator !== "in") return;
+        if (!t.isPrivateName(node.left)) return;
+
+        const { name } = node.left.id;
+
+        let privateElement;
+        const outerClass = path.findParent(path => {
+          if (!path.isClass()) return false;
+
+          privateElement = path
+            .get("body.body")
+            .find(({ node }) => t.isPrivate(node) && node.key.id.name === name);
+
+          return !!privateElement;
+        });
+
+        if (outerClass.parentPath.scope.path.isPattern()) {
+          outerClass.replaceWith(template.ast`(() => ${outerClass.node})()`);
+          // The injected class will be queued and eventually transformed when visited
+          return;
+        }
+
+        if (privateElement.isMethod()) {
+          if (privateElement.node.static) {
+            if (outerClass.node.id) {
+              unshadow(outerClass.node.id.name, outerClass.scope, path.scope);
+            } else {
+              outerClass.set("id", path.scope.generateUidIdentifier("class"));
+            }
+            path.replaceWith(
+              template.expression.ast`
+                ${t.cloneNode(outerClass.node.id)} === ${path.node.right}
+              `,
+            );
+          } else {
+            const id = getWeakSetId(
+              classWeakSets,
+              outerClass,
+              outerClass,
+              outerClass.node.id?.name,
+              injectInitialization,
+            );
 
-  return createClassFeaturePlugin({
-    name: "proposal-class-properties",
+            path.replaceWith(
+              template.expression.ast`${id}.has(${path.node.right})`,
+            );
+          }
+        } else {
+          // Private fields might not all be initialized: see the 'halfConstructed'
+          // example at https://v8.dev/features/private-brand-checks.
 
-    api,
-    feature: FEATURES.privateIn,
-    loose: options.loose,
+          const id = getWeakSetId(
+            fieldsWeakSets,
+            outerClass,
+            privateElement,
+            privateElement.node.key.id.name,
+            injectToFieldInit,
+          );
 
-    manipulateOptions(opts, parserOpts) {
-      parserOpts.plugins.push("privateIn");
+          path.replaceWith(
+            template.expression.ast`${id}.has(${path.node.right})`,
+          );
+        }
+      },
     },
-  });
+  };
 });

packages/babel-plugin-proposal-private-property-in-object/test/fixtures/to-native-fields/accessor/input.js

@@ -0,0 +1,7 @@
+class Foo {
+  get #foo() {}
+
+  test(other) {
+    return #foo in other;
+  }
+}

packages/babel-plugin-proposal-private-property-in-object/test/fixtures/to-native-fields/accessor/output.js

@@ -0,0 +1,14 @@
+var _FooBrandCheck = new WeakSet();
+
+class Foo {
+  constructor() {
+    _FooBrandCheck.add(this);
+  }
+
+  get #foo() {}
+
+  test(other) {
+    return _FooBrandCheck.has(other);
+  }
+
+}

packages/babel-plugin-proposal-private-property-in-object/test/fixtures/to-native-fields/class-expression-in-default-param/input.js

@@ -0,0 +1,4 @@
+(x = class {
+  #foo;
+  test(other) { return #foo in other }
+}) => {}

packages/babel-plugin-proposal-private-property-in-object/test/fixtures/to-native-fields/class-expression-in-default-param/output.js

@@ -0,0 +1,12 @@
+(x = (() => {
+  var _fooBrandCheck;
+
+  return _fooBrandCheck = new WeakSet(), class {
+    #foo = void _fooBrandCheck.add(this);
+
+    test(other) {
+      return _fooBrandCheck.has(other);
+    }
+
+  };
+})()) => {};

packages/babel-plugin-proposal-private-property-in-object/test/fixtures/to-native-fields/class-expression-instance/input.js

@@ -0,0 +1,9 @@
+function fn() {
+  return new class {
+    #priv;
+
+    method(obj) {
+      return #priv in obj;
+    }
+  }
+}

packages/babel-plugin-proposal-private-property-in-object/test/fixtures/to-native-fields/class-expression-instance/output.js

@@ -0,0 +1,12 @@
+function fn() {
+  var _privBrandCheck;
+
+  return new (_privBrandCheck = new WeakSet(), class {
+    #priv = void _privBrandCheck.add(this);
+
+    method(obj) {
+      return _privBrandCheck.has(obj);
+    }
+
+  })();
+}

packages/babel-plugin-proposal-private-property-in-object/test/fixtures/to-native-fields/class-expression-static/input.js

@@ -0,0 +1,9 @@
+function fn() {
+  return new class {
+    static #priv;
+
+    method(obj) {
+      return #priv in obj;
+    }
+  }
+}

packages/babel-plugin-proposal-private-property-in-object/test/fixtures/to-native-fields/class-expression-static/output.js

@@ -0,0 +1,12 @@
+function fn() {
+  var _privBrandCheck;
+
+  return new (_privBrandCheck = new WeakSet(), class {
+    static #priv = void _privBrandCheck.add(this);
+
+    method(obj) {
+      return _privBrandCheck.has(obj);
+    }
+
+  })();
+}

packages/babel-plugin-proposal-private-property-in-object/test/fixtures/to-native-fields/field/input.js

@@ -0,0 +1,7 @@
+class Foo {
+  #foo = 1;
+
+  test(other) {
+    return #foo in other;
+  }
+}

packages/babel-plugin-proposal-private-property-in-object/test/fixtures/to-native-fields/field/output.js

@@ -0,0 +1,12 @@
+var _temp;
+
+var _fooBrandCheck = new WeakSet();
+
+class Foo {
+  #foo = (_temp = 1, _fooBrandCheck.add(this), _temp);
+
+  test(other) {
+    return _fooBrandCheck.has(other);
+  }
+
+}

packages/babel-plugin-proposal-private-property-in-object/test/fixtures/to-native-fields/half-constructed-instance/exec.js

@@ -0,0 +1,28 @@
+let hasW, hasX, hasY, hasZ;
+let halfConstructed;
+
+class F {
+  m() {
+    hasW = #w in this;
+    hasX = #x in this;
+    hasY = #y in this;
+    hasZ = #z in this;
+  }
+  get #w() {}
+  #x = 0;
+  #y = (() => {
+    halfConstructed = this;
+    throw "error";
+  })();
+  #z() {}
+}
+
+try {
+  new F();
+} catch {}
+halfConstructed.m();
+
+expect(hasW).toBe(true);
+expect(hasX).toBe(true);
+expect(hasY).toBe(false);
+expect(hasZ).toBe(true);

packages/babel-plugin-proposal-private-property-in-object/test/fixtures/to-native-fields/half-constructed-instance/input.js

@@ -0,0 +1,14 @@
+class F {
+  m() {
+    #w in this;
+    #x in this;
+    #y in this;
+    #z in this;
+  }
+  get #w() {}
+  #x = 0;
+  #y = (() => {
+    throw 'error';
+  })();
+  #z() {}
+}

packages/babel-plugin-proposal-private-property-in-object/test/fixtures/to-native-fields/half-constructed-instance/options.json

@@ -0,0 +1,3 @@
+{
+  "minNodeVersion": "14.0.0"
+}

packages/babel-plugin-proposal-private-property-in-object/test/fixtures/to-native-fields/half-constructed-instance/output.js

@@ -0,0 +1,29 @@
+var _temp, _temp2;
+
+var _FBrandCheck = new WeakSet();
+
+var _xBrandCheck = new WeakSet();
+
+var _yBrandCheck = new WeakSet();
+
+class F {
+  m() {
+    _FBrandCheck.has(this);
+
+    _xBrandCheck.has(this);
+
+    _yBrandCheck.has(this);
+
+    _FBrandCheck.has(this);
+  }
+
+  get #w() {}
+
+  #x = (_temp = (_FBrandCheck.add(this), 0), _xBrandCheck.add(this), _temp);
+  #y = (_temp2 = (() => {
+    throw 'error';
+  })(), _yBrandCheck.add(this), _temp2);
+
+  #z() {}
+
+}