94 lines
2.5 KiB
TypeScript
94 lines
2.5 KiB
TypeScript
/**
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* This adds a __self={this} JSX attribute to all JSX elements, which React will use
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* to generate some runtime warnings. However, if the JSX element appears within a
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* constructor of a derived class, `__self={this}` will not be inserted in order to
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* prevent runtime errors.
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*
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* == JSX Literals ==
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*
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* <sometag />
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*
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* becomes:
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*
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* <sometag __self={this} />
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*/
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import { declare } from "@babel/helper-plugin-utils";
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import { types as t } from "@babel/core";
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const TRACE_ID = "__self";
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/**
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* Finds the closest parent function that provides `this`. Specifically, this looks for
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* the first parent function that isn't an arrow function.
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*
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* Derived from `Scope#getFunctionParent`
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*/
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function getThisFunctionParent(path) {
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let scope = path.scope;
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do {
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if (
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scope.path.isFunctionParent() &&
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!scope.path.isArrowFunctionExpression()
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) {
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return scope.path;
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}
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} while ((scope = scope.parent));
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return null;
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}
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/**
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* Returns whether the class has specified a superclass.
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*/
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function isDerivedClass(classPath) {
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return classPath.node.superClass !== null;
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}
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/**
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* Returns whether `this` is allowed at given path.
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*/
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function isThisAllowed(path) {
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// This specifically skips arrow functions as they do not rewrite `this`.
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const parentMethodOrFunction = getThisFunctionParent(path);
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if (parentMethodOrFunction === null) {
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// We are not in a method or function. It is fine to use `this`.
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return true;
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}
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if (!parentMethodOrFunction.isMethod()) {
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// If the closest parent is a regular function, `this` will be rebound, therefore it is fine to use `this`.
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return true;
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}
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// Current node is within a method, so we need to check if the method is a constructor.
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if (parentMethodOrFunction.node.kind !== "constructor") {
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// We are not in a constructor, therefore it is always fine to use `this`.
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return true;
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}
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// Now we are in a constructor. If it is a derived class, we do not reference `this`.
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return !isDerivedClass(parentMethodOrFunction.parentPath.parentPath);
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}
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export default declare(api => {
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api.assertVersion(7);
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const visitor = {
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JSXOpeningElement(path) {
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if (!isThisAllowed(path)) {
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return;
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}
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const node = path.node;
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const id = t.jsxIdentifier(TRACE_ID);
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const trace = t.thisExpression();
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node.attributes.push(t.jsxAttribute(id, t.jsxExpressionContainer(trace)));
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},
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};
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return {
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name: "transform-react-jsx-self",
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visitor: {
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Program(path) {
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path.traverse(visitor);
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},
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},
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};
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});
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