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index.js
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index.js
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import { declare } from "@babel/helper-plugin-utils";
import syntaxPlugin from "@babel/plugin-syntax-private-property-in-object";
import {
enableFeature,
FEATURES,
injectInitialization as injectConstructorInit,
} from "@babel/helper-create-class-features-plugin";
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)} === ${path.node.right}
`,
);
} else {
const id = getWeakSetId(
classWeakSets,
outerClass,
outerClass,
outerClass.node.id?.name,
injectInitialization,
);
path.replaceWith(
template.expression.ast`${id}.has(${path.node.right})`,
);
}
} else {
// Private fields might not all be initialized: see the 'halfConstructed'
// example at https://v8.dev/features/private-brand-checks.
const id = getWeakSetId(
fieldsWeakSets,
outerClass,
privateElement,
privateElement.node.key.id.name,
injectToFieldInit,
);
path.replaceWith(
template.expression.ast`${id}.has(${path.node.right})`,
);
}
},
},
};
});