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