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Runtime error
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'use strict';
const { hasOwnProperty } = Object.prototype;
const noop = function() {};
function ensureFunction(value) {
return typeof value === 'function' ? value : noop;
}
function invokeForType(fn, type) {
return function(node, item, list) {
if (node.type === type) {
fn.call(this, node, item, list);
}
};
}
function getWalkersFromStructure(name, nodeType) {
const structure = nodeType.structure;
const walkers = [];
for (const key in structure) {
if (hasOwnProperty.call(structure, key) === false) {
continue;
}
let fieldTypes = structure[key];
const walker = {
name: key,
type: false,
nullable: false
};
if (!Array.isArray(fieldTypes)) {
fieldTypes = [fieldTypes];
}
for (const fieldType of fieldTypes) {
if (fieldType === null) {
walker.nullable = true;
} else if (typeof fieldType === 'string') {
walker.type = 'node';
} else if (Array.isArray(fieldType)) {
walker.type = 'list';
}
}
if (walker.type) {
walkers.push(walker);
}
}
if (walkers.length) {
return {
context: nodeType.walkContext,
fields: walkers
};
}
return null;
}
function getTypesFromConfig(config) {
const types = {};
for (const name in config.node) {
if (hasOwnProperty.call(config.node, name)) {
const nodeType = config.node[name];
if (!nodeType.structure) {
throw new Error('Missed `structure` field in `' + name + '` node type definition');
}
types[name] = getWalkersFromStructure(name, nodeType);
}
}
return types;
}
function createTypeIterator(config, reverse) {
const fields = config.fields.slice();
const contextName = config.context;
const useContext = typeof contextName === 'string';
if (reverse) {
fields.reverse();
}
return function(node, context, walk, walkReducer) {
let prevContextValue;
if (useContext) {
prevContextValue = context[contextName];
context[contextName] = node;
}
for (const field of fields) {
const ref = node[field.name];
if (!field.nullable || ref) {
if (field.type === 'list') {
const breakWalk = reverse
? ref.reduceRight(walkReducer, false)
: ref.reduce(walkReducer, false);
if (breakWalk) {
return true;
}
} else if (walk(ref)) {
return true;
}
}
}
if (useContext) {
context[contextName] = prevContextValue;
}
};
}
function createFastTraveralMap({
StyleSheet,
Atrule,
Rule,
Block,
DeclarationList
}) {
return {
Atrule: {
StyleSheet,
Atrule,
Rule,
Block
},
Rule: {
StyleSheet,
Atrule,
Rule,
Block
},
Declaration: {
StyleSheet,
Atrule,
Rule,
Block,
DeclarationList
}
};
}
function createWalker(config) {
const types = getTypesFromConfig(config);
const iteratorsNatural = {};
const iteratorsReverse = {};
const breakWalk = Symbol('break-walk');
const skipNode = Symbol('skip-node');
for (const name in types) {
if (hasOwnProperty.call(types, name) && types[name] !== null) {
iteratorsNatural[name] = createTypeIterator(types[name], false);
iteratorsReverse[name] = createTypeIterator(types[name], true);
}
}
const fastTraversalIteratorsNatural = createFastTraveralMap(iteratorsNatural);
const fastTraversalIteratorsReverse = createFastTraveralMap(iteratorsReverse);
const walk = function(root, options) {
function walkNode(node, item, list) {
const enterRet = enter.call(context, node, item, list);
if (enterRet === breakWalk) {
return true;
}
if (enterRet === skipNode) {
return false;
}
if (iterators.hasOwnProperty(node.type)) {
if (iterators[node.type](node, context, walkNode, walkReducer)) {
return true;
}
}
if (leave.call(context, node, item, list) === breakWalk) {
return true;
}
return false;
}
let enter = noop;
let leave = noop;
let iterators = iteratorsNatural;
let walkReducer = (ret, data, item, list) => ret || walkNode(data, item, list);
const context = {
break: breakWalk,
skip: skipNode,
root,
stylesheet: null,
atrule: null,
atrulePrelude: null,
rule: null,
selector: null,
block: null,
declaration: null,
function: null
};
if (typeof options === 'function') {
enter = options;
} else if (options) {
enter = ensureFunction(options.enter);
leave = ensureFunction(options.leave);
if (options.reverse) {
iterators = iteratorsReverse;
}
if (options.visit) {
if (fastTraversalIteratorsNatural.hasOwnProperty(options.visit)) {
iterators = options.reverse
? fastTraversalIteratorsReverse[options.visit]
: fastTraversalIteratorsNatural[options.visit];
} else if (!types.hasOwnProperty(options.visit)) {
throw new Error('Bad value `' + options.visit + '` for `visit` option (should be: ' + Object.keys(types).sort().join(', ') + ')');
}
enter = invokeForType(enter, options.visit);
leave = invokeForType(leave, options.visit);
}
}
if (enter === noop && leave === noop) {
throw new Error('Neither `enter` nor `leave` walker handler is set or both aren\'t a function');
}
walkNode(root);
};
walk.break = breakWalk;
walk.skip = skipNode;
walk.find = function(ast, fn) {
let found = null;
walk(ast, function(node, item, list) {
if (fn.call(this, node, item, list)) {
found = node;
return breakWalk;
}
});
return found;
};
walk.findLast = function(ast, fn) {
let found = null;
walk(ast, {
reverse: true,
enter(node, item, list) {
if (fn.call(this, node, item, list)) {
found = node;
return breakWalk;
}
}
});
return found;
};
walk.findAll = function(ast, fn) {
const found = [];
walk(ast, function(node, item, list) {
if (fn.call(this, node, item, list)) {
found.push(node);
}
});
return found;
};
return walk;
}
exports.createWalker = createWalker;
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