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362 lines
9.3 KiB
362 lines
9.3 KiB
4 months ago
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import { devAssert } from '../jsutils/devAssert.mjs';
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import { inspect } from '../jsutils/inspect.mjs';
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import { isNode, QueryDocumentKeys } from './ast.mjs';
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import { Kind } from './kinds.mjs';
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/**
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* A visitor is provided to visit, it contains the collection of
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* relevant functions to be called during the visitor's traversal.
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*/
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export const BREAK = Object.freeze({});
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/**
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* visit() will walk through an AST using a depth-first traversal, calling
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* the visitor's enter function at each node in the traversal, and calling the
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* leave function after visiting that node and all of its child nodes.
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*
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* By returning different values from the enter and leave functions, the
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* behavior of the visitor can be altered, including skipping over a sub-tree of
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* the AST (by returning false), editing the AST by returning a value or null
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* to remove the value, or to stop the whole traversal by returning BREAK.
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*
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* When using visit() to edit an AST, the original AST will not be modified, and
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* a new version of the AST with the changes applied will be returned from the
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* visit function.
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*
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* ```ts
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* const editedAST = visit(ast, {
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* enter(node, key, parent, path, ancestors) {
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* // @return
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* // undefined: no action
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* // false: skip visiting this node
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* // visitor.BREAK: stop visiting altogether
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* // null: delete this node
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* // any value: replace this node with the returned value
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* },
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* leave(node, key, parent, path, ancestors) {
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* // @return
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* // undefined: no action
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* // false: no action
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* // visitor.BREAK: stop visiting altogether
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* // null: delete this node
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* // any value: replace this node with the returned value
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* }
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* });
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* ```
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*
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* Alternatively to providing enter() and leave() functions, a visitor can
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* instead provide functions named the same as the kinds of AST nodes, or
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* enter/leave visitors at a named key, leading to three permutations of the
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* visitor API:
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*
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* 1) Named visitors triggered when entering a node of a specific kind.
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*
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* ```ts
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* visit(ast, {
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* Kind(node) {
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* // enter the "Kind" node
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* }
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* })
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* ```
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*
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* 2) Named visitors that trigger upon entering and leaving a node of a specific kind.
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*
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* ```ts
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* visit(ast, {
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* Kind: {
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* enter(node) {
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* // enter the "Kind" node
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* }
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* leave(node) {
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* // leave the "Kind" 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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* 3) Generic visitors that trigger upon entering and leaving any node.
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*
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* ```ts
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* visit(ast, {
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* enter(node) {
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* // enter any node
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* },
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* leave(node) {
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* // leave any node
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* }
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* })
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* ```
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*/
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export function visit(root, visitor, visitorKeys = QueryDocumentKeys) {
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const enterLeaveMap = new Map();
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for (const kind of Object.values(Kind)) {
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enterLeaveMap.set(kind, getEnterLeaveForKind(visitor, kind));
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}
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/* eslint-disable no-undef-init */
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let stack = undefined;
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let inArray = Array.isArray(root);
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let keys = [root];
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let index = -1;
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let edits = [];
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let node = root;
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let key = undefined;
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let parent = undefined;
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const path = [];
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const ancestors = [];
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/* eslint-enable no-undef-init */
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do {
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index++;
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const isLeaving = index === keys.length;
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const isEdited = isLeaving && edits.length !== 0;
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if (isLeaving) {
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key = ancestors.length === 0 ? undefined : path[path.length - 1];
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node = parent;
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parent = ancestors.pop();
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if (isEdited) {
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if (inArray) {
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node = node.slice();
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let editOffset = 0;
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for (const [editKey, editValue] of edits) {
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const arrayKey = editKey - editOffset;
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if (editValue === null) {
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node.splice(arrayKey, 1);
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editOffset++;
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} else {
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node[arrayKey] = editValue;
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}
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}
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} else {
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node = Object.defineProperties(
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{},
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Object.getOwnPropertyDescriptors(node),
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);
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for (const [editKey, editValue] of edits) {
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node[editKey] = editValue;
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}
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}
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}
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index = stack.index;
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keys = stack.keys;
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edits = stack.edits;
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inArray = stack.inArray;
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stack = stack.prev;
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} else if (parent) {
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key = inArray ? index : keys[index];
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node = parent[key];
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if (node === null || node === undefined) {
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continue;
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}
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path.push(key);
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}
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let result;
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if (!Array.isArray(node)) {
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var _enterLeaveMap$get, _enterLeaveMap$get2;
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isNode(node) || devAssert(false, `Invalid AST Node: ${inspect(node)}.`);
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const visitFn = isLeaving
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? (_enterLeaveMap$get = enterLeaveMap.get(node.kind)) === null ||
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_enterLeaveMap$get === void 0
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? void 0
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: _enterLeaveMap$get.leave
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: (_enterLeaveMap$get2 = enterLeaveMap.get(node.kind)) === null ||
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_enterLeaveMap$get2 === void 0
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? void 0
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: _enterLeaveMap$get2.enter;
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result =
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visitFn === null || visitFn === void 0
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? void 0
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: visitFn.call(visitor, node, key, parent, path, ancestors);
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if (result === BREAK) {
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break;
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}
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if (result === false) {
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if (!isLeaving) {
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path.pop();
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continue;
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}
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} else if (result !== undefined) {
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edits.push([key, result]);
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if (!isLeaving) {
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if (isNode(result)) {
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node = result;
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} else {
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path.pop();
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continue;
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}
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}
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}
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}
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if (result === undefined && isEdited) {
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edits.push([key, node]);
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}
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if (isLeaving) {
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path.pop();
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} else {
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var _node$kind;
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stack = {
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inArray,
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index,
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keys,
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edits,
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prev: stack,
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};
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inArray = Array.isArray(node);
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keys = inArray
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? node
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: (_node$kind = visitorKeys[node.kind]) !== null &&
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_node$kind !== void 0
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? _node$kind
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: [];
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index = -1;
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edits = [];
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if (parent) {
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ancestors.push(parent);
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}
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parent = node;
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}
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} while (stack !== undefined);
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if (edits.length !== 0) {
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// New root
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return edits[edits.length - 1][1];
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}
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return root;
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}
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/**
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* Creates a new visitor instance which delegates to many visitors to run in
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* parallel. Each visitor will be visited for each node before moving on.
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*
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* If a prior visitor edits a node, no following visitors will see that node.
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*/
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export function visitInParallel(visitors) {
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const skipping = new Array(visitors.length).fill(null);
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const mergedVisitor = Object.create(null);
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for (const kind of Object.values(Kind)) {
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let hasVisitor = false;
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const enterList = new Array(visitors.length).fill(undefined);
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const leaveList = new Array(visitors.length).fill(undefined);
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for (let i = 0; i < visitors.length; ++i) {
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const { enter, leave } = getEnterLeaveForKind(visitors[i], kind);
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hasVisitor || (hasVisitor = enter != null || leave != null);
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enterList[i] = enter;
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leaveList[i] = leave;
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}
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if (!hasVisitor) {
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continue;
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}
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const mergedEnterLeave = {
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enter(...args) {
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const node = args[0];
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for (let i = 0; i < visitors.length; i++) {
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if (skipping[i] === null) {
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var _enterList$i;
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const result =
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(_enterList$i = enterList[i]) === null || _enterList$i === void 0
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? void 0
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: _enterList$i.apply(visitors[i], args);
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if (result === false) {
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skipping[i] = node;
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} else if (result === BREAK) {
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skipping[i] = BREAK;
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} else if (result !== undefined) {
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return result;
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}
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}
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}
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},
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leave(...args) {
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const node = args[0];
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for (let i = 0; i < visitors.length; i++) {
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if (skipping[i] === null) {
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var _leaveList$i;
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const result =
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(_leaveList$i = leaveList[i]) === null || _leaveList$i === void 0
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? void 0
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: _leaveList$i.apply(visitors[i], args);
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if (result === BREAK) {
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skipping[i] = BREAK;
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} else if (result !== undefined && result !== false) {
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return result;
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}
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} else if (skipping[i] === node) {
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skipping[i] = null;
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}
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}
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},
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};
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mergedVisitor[kind] = mergedEnterLeave;
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}
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return mergedVisitor;
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}
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/**
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* Given a visitor instance and a node kind, return EnterLeaveVisitor for that kind.
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*/
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export function getEnterLeaveForKind(visitor, kind) {
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const kindVisitor = visitor[kind];
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if (typeof kindVisitor === 'object') {
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// { Kind: { enter() {}, leave() {} } }
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return kindVisitor;
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} else if (typeof kindVisitor === 'function') {
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// { Kind() {} }
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return {
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enter: kindVisitor,
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leave: undefined,
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};
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} // { enter() {}, leave() {} }
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return {
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enter: visitor.enter,
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leave: visitor.leave,
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};
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}
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/**
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* Given a visitor instance, if it is leaving or not, and a node kind, return
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* the function the visitor runtime should call.
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*
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* @deprecated Please use `getEnterLeaveForKind` instead. Will be removed in v17
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*/
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/* c8 ignore next 8 */
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export function getVisitFn(visitor, kind, isLeaving) {
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const { enter, leave } = getEnterLeaveForKind(visitor, kind);
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return isLeaving ? leave : enter;
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}
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