144 lines
4.4 KiB
Plaintext
144 lines
4.4 KiB
Plaintext
/**
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* Copyright (c) Meta Platforms, Inc. and affiliates.
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*
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* This source code is licensed under the MIT license found in the
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* LICENSE file in the root directory of this source tree.
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*
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* @flow strict
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* @format
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*/
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'use strict';
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import type {VisitorKeysType} from '../traverse/getVisitorKeys';
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import type {ESNode, Program} from 'hermes-estree';
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import {SimpleTraverser} from '../traverse/SimpleTraverser';
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import {
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nodeWith,
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removeNodeOnParent,
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replaceNodeOnParent,
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} from './astNodeMutationHelpers';
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/**
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* Transform callback
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* @param node The node we are visiting
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* @returns
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* - return input node, signals no changes were made will continue to the next node.
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* - return new node, the old node will be replaced in the AST. The new node and its
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* children are then traversed.
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* - return null, signals the node should be deleted from the AST.
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*/
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export type TransformCallback = (node: ESNode) => ESNode | null;
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export type TransformOptions = $ReadOnly<{
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/** The callback function which is called on entering each node. */
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transform: TransformCallback,
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/** The set of visitor keys to use for traversal. Defaults to the Flow ESTree visitor keys */
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visitorKeys?: ?VisitorKeysType,
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}>;
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function setParentPointer(node: ESNode, parent: ?ESNode): void {
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if (parent != null) {
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// $FlowExpectedError[cannot-write]
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node.parent = parent;
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}
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}
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/**
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* A simple class to recursively tranform AST trees.
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*/
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export class SimpleTransform {
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/**
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* Transform the given AST tree.
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* @param rootNode The root node to traverse.
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* @param options The option object.
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* @return The modified rootNode or a new node if the rootNode was transformed directly.
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*/
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transform(rootNode: ESNode, options: TransformOptions): ESNode | null {
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let resultRootNode: ESNode | null = rootNode;
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SimpleTraverser.traverse(rootNode, {
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enter: (node: ESNode, parent: ?ESNode) => {
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// Ensure the parent pointers are correctly set before entering the node.
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setParentPointer(node, parent);
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const resultNode = options.transform(node);
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if (resultNode !== node) {
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let traversedResultNode = null;
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if (resultNode != null) {
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// Ensure the new node has the correct parent pointers before recursing again.
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setParentPointer(resultNode, parent);
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traversedResultNode = this.transform(resultNode, options);
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}
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if (parent == null) {
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if (node !== rootNode) {
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throw new Error(
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'SimpleTransform infra error: Parent not set on non root node, this should not be possible',
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);
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}
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resultRootNode = traversedResultNode;
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} else if (traversedResultNode == null) {
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removeNodeOnParent(node, parent, options.visitorKeys);
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} else {
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replaceNodeOnParent(
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node,
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parent,
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traversedResultNode,
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options.visitorKeys,
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);
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setParentPointer(traversedResultNode, parent);
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}
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throw SimpleTraverser.Skip;
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}
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},
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leave(_node: ESNode) {},
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visitorKeys: options.visitorKeys,
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});
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return resultRootNode;
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}
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/**
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* Transform the given AST tree.
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* @param node The root node to traverse.
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* @param options The option object.
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*/
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static transform(node: ESNode, options: TransformOptions): ESNode | null {
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return new SimpleTransform().transform(node, options);
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}
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static transformProgram(
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program: Program,
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options: TransformOptions,
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): Program {
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const result = SimpleTransform.transform(program, options);
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if (result?.type === 'Program') {
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return result;
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}
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throw new Error('SimpleTransform.transformProgram: Expected program node.');
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}
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/**
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* Return a new AST node with the given properties overrided if needed.
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*
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* This function takes care to only create new nodes when needed. Referential equality of nodes
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* is important as its used to know if a node should be re-traversed.
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*
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* @param node The base AST node.
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* @param overrideProps New properties to apply to the node.
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* @return Either the orginal node if the properties matched the existing node or a new node with
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* the new properties.
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*/
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static nodeWith<T: ESNode>(
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node: T,
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overrideProps: Partial<T>,
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visitorKeys?: VisitorKeysType,
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): T {
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return nodeWith<T>(node, overrideProps, visitorKeys);
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}
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}
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