0345c1bc1d
In https://github.com/babel/babel/issues/9511 (and #9495 is another symptom), @PavelKastornyy reported a node crash becaue the JavaScript heap run out of memory. The problem was that their code was adding enumerable properties to `Object.prototype`: it is something that shouldn't be done, but Babel shouldn't make node crash if someone adds them. I reduced down the problem to `for...in` loops in `@babel/traverse` that grew the memory consumption exponentially because of that unexpected properties.
102 lines
2.5 KiB
JavaScript
102 lines
2.5 KiB
JavaScript
import { types as t } from "@babel/core";
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function getTDZStatus(refPath, bindingPath) {
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const executionStatus = bindingPath._guessExecutionStatusRelativeTo(refPath);
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if (executionStatus === "before") {
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return "inside";
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} else if (executionStatus === "after") {
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return "outside";
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} else {
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return "maybe";
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}
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}
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function buildTDZAssert(node, state) {
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return t.callExpression(state.addHelper("temporalRef"), [
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node,
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t.stringLiteral(node.name),
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]);
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}
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function isReference(node, scope, state) {
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const declared = state.letReferences[node.name];
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if (!declared) return false;
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// declared node is different in this scope
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return scope.getBindingIdentifier(node.name) === declared;
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}
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export const visitor = {
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ReferencedIdentifier(path, state) {
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if (!state.tdzEnabled) return;
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const { node, parent, scope } = path;
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if (path.parentPath.isFor({ left: node })) return;
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if (!isReference(node, scope, state)) return;
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const bindingPath = scope.getBinding(node.name).path;
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if (bindingPath.isFunctionDeclaration()) return;
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const status = getTDZStatus(path, bindingPath);
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if (status === "inside") return;
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if (status === "maybe") {
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const assert = buildTDZAssert(node, state);
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// add tdzThis to parent variable declarator so it's exploded
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bindingPath.parent._tdzThis = true;
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path.skip();
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if (path.parentPath.isUpdateExpression()) {
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if (parent._ignoreBlockScopingTDZ) return;
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path.parentPath.replaceWith(t.sequenceExpression([assert, parent]));
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} else {
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path.replaceWith(assert);
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}
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} else if (status === "outside") {
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path.replaceWith(
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t.throwStatement(
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t.inherits(
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t.newExpression(t.identifier("ReferenceError"), [
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t.stringLiteral(
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`${node.name} is not defined - temporal dead zone`,
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),
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]),
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node,
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),
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),
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);
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}
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},
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AssignmentExpression: {
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exit(path, state) {
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if (!state.tdzEnabled) return;
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const { node } = path;
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if (node._ignoreBlockScopingTDZ) return;
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const nodes = [];
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const ids = path.getBindingIdentifiers();
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for (const name of Object.keys(ids)) {
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const id = ids[name];
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if (isReference(id, path.scope, state)) {
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nodes.push(buildTDZAssert(id, state));
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}
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}
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if (nodes.length) {
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node._ignoreBlockScopingTDZ = true;
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nodes.push(node);
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path.replaceWithMultiple(nodes.map(t.expressionStatement));
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}
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},
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},
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};
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