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Replace stack based tree traversal in extractNodesFromRoot with a Visitor pattern. #44

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Replace stack based tree traversal in extractNodesFromRoot with a Visitor pattern. #44

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2f7295f
Replace getter property with string reference.
aliceofhartley Feb 17, 2026
fb3afb8
Update comment.
aliceofhartley Feb 17, 2026
a2e3b70
Seperate node parsing from traversal.
aliceofhartley Feb 16, 2026
10f972f
Convert extractNodesFromRoot traversal to be stack-less.
aliceofhartley Feb 16, 2026
ba2d6a1
Replace for loop with map.
aliceofhartley Feb 17, 2026
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135 changes: 75 additions & 60 deletions src/flast.js
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Original file line number Diff line number Diff line change
Expand Up @@ -38,15 +38,6 @@ const generateFlatASTDefaultOptions = {
},
};

/**
* Return a function which retrieves a node's source on demand
* @param {string} src
* @returns {function(number, number): string}
*/
function createSrcClosure(src) {
return function(start, end) {return src.slice(start, end);};
}

/**
* @param {string} inputCode
* @param {object} opts Optional changes to behavior. See generateFlatASTDefaultOptions for available options.
Expand Down Expand Up @@ -96,13 +87,13 @@ function generateRootNode(inputCode, opts = {}) {
let rootNode;
try {
rootNode = parseCode(inputCode, parseOpts);
if (opts.includeSrc) rootNode.srcClosure = createSrcClosure(inputCode);
if (opts.includeSrc) rootNode.src = inputCode;
} catch (e) {
// If any parse error occurs and alternateSourceTypeOnFailure is set, try 'script' mode
if (opts.alternateSourceTypeOnFailure) {
try {
rootNode = parseCode(inputCode, {...parseOpts, sourceType: 'script'});
if (opts.includeSrc) rootNode.srcClosure = createSrcClosure(inputCode);
if (opts.includeSrc) rootNode.src = inputCode;
} catch (e2) {
logger.debug('Failed to parse as module and script:', e, e2);
}
Expand All @@ -113,69 +104,93 @@ function generateRootNode(inputCode, opts = {}) {
return rootNode;
}

/**
* @param {object} opts
* @param {ASTNode} rootNode
* @param {{number: ASTScope}} scopes
* @param {number} nodeId
* @param {ASTNode} node
* @return {ASTNode}
*/
function parseNode (opts, rootNode, scopes, nodeId, node) {
if (node.nodeId) return;
node.childNodes = node.childNodes || [];
const childrenLoc = {}; // Store the location of child nodes to sort them by order
node.parentKey = node.parentKey || ''; // Make sure parentKey exists
// Iterate over all keys of the node to find child nodes
const keys = Object.keys(node);
for (let i = 0; i < keys.length; i++) {
const key = keys[i];
if (excludedParentKeys.includes(key)) continue;
const content = node[key];
if (content && typeof content === 'object') {
// Sort each child node by its start position
// and set the parentNode and parentKey attributes
if (Array.isArray(content)) {
for (let j = 0; j < content.length; j++) {
const childNode = content[j];
if (!childNode) continue;
childNode.parentNode = node;
childNode.parentKey = key;
childrenLoc[childNode.start] = childNode;
}
} else {
content.parentNode = node;
content.parentKey = key;
childrenLoc[content.start] = content;
}
}
}
// Add the child nodes to top of the stack and populate the node's childNodes array
node.childNodes.push(...Object.values(childrenLoc));

node.nodeId = nodeId;
if (opts.detailed) {
node.scope = scopes[node.scopeId] || node.parentNode?.scope;
node.lineage = [...node.parentNode?.lineage || []];
if (!node.lineage.includes(node.scope.scopeId)) {
node.lineage.push(node.scope.scopeId);
}
}
// Avoid using a getter with a closure around source here, as the
// memory requirement for a function per node is far greater than using
// a string reference for sufficiently large AST Trees
// (~2.4 nodes for 3 Gib).
if (opts.includeSrc && !node.src)
node.src = rootNode.src.substring(node.start,node.end);
return node;
}

/**
* @param rootNode
* @param opts
* @return {ASTNode[]}
*/
function extractNodesFromRoot(rootNode, opts) {
opts = {...generateFlatASTDefaultOptions, ...opts};
let nodeId = 0;
const typeMap = {};
const allNodes = [];
const scopes = opts.detailed ? getAllScopes(rootNode) : {};

const stack = [rootNode];
while (stack.length) {
const node = stack.shift();
if (node.nodeId) continue;
node.childNodes = node.childNodes || [];
const childrenLoc = {}; // Store the location of child nodes to sort them by order
node.parentKey = node.parentKey || ''; // Make sure parentKey exists
// Iterate over all keys of the node to find child nodes
const keys = Object.keys(node);
for (let i = 0; i < keys.length; i++) {
const key = keys[i];
if (excludedParentKeys.includes(key)) continue;
const content = node[key];
if (content && typeof content === 'object') {
// Sort each child node by its start position
// and set the parentNode and parentKey attributes
if (Array.isArray(content)) {
for (let j = 0; j < content.length; j++) {
const childNode = content[j];
if (!childNode) continue;
childNode.parentNode = node;
childNode.parentKey = key;
childrenLoc[childNode.start] = childNode;
}
} else {
content.parentNode = node;
content.parentKey = key;
childrenLoc[content.start] = content;
}
}
let nodeId = 0;
let visitor = rootNode;
const lastParsed = {};
while (visitor) {
if(!visitor.childNodes){
allNodes.push(parseNode(opts, rootNode, scopes, nodeId++, visitor));
typeMap[visitor.type] = typeMap[visitor.type] || [];
typeMap[visitor.type].push(visitor);
lastParsed[visitor.nodeId] = 0;
}
// Add the child nodes to top of the stack and populate the node's childNodes array
stack.unshift(...Object.values(childrenLoc));
node.childNodes.push(...Object.values(childrenLoc));

allNodes.push(node);
node.nodeId = nodeId++;
typeMap[node.type] = typeMap[node.type] || [];
typeMap[node.type].push(node);
if (opts.detailed) {
node.scope = scopes[node.scopeId] || node.parentNode?.scope;
node.lineage = [...node.parentNode?.lineage || []];
if (!node.lineage.includes(node.scope.scopeId)) {
node.lineage.push(node.scope.scopeId);
}
let visitorId = visitor.nodeId;
if(lastParsed[visitorId] < visitor.childNodes.length){
visitor = visitor.childNodes[lastParsed[visitorId]++];
}else{
visitor = visitor.parentNode;
delete lastParsed[visitorId];
}
// Add a getter for the node's source code
if (opts.includeSrc && !node.src) Object.defineProperty(node, 'src', {
get() {return rootNode.srcClosure(node.start, node.end);},
});
}

if (opts.detailed) {
const identifiers = typeMap.Identifier || [];
const scopeVarMaps = buildScopeVarMaps(scopes);
Expand Down