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262 lines
6.9 KiB
262 lines
6.9 KiB
var hasOwnProperty = Object.prototype.hasOwnProperty;
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var noop = function() {};
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function ensureFunction(value) {
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return typeof value === 'function' ? value : noop;
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}
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function invokeForType(fn, type) {
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return function(node, item, list) {
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if (node.type === type) {
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fn.call(this, node, item, list);
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}
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};
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}
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function getWalkersFromStructure(name, nodeType) {
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var structure = nodeType.structure;
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var walkers = [];
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for (var key in structure) {
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if (hasOwnProperty.call(structure, key) === false) {
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continue;
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}
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var fieldTypes = structure[key];
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var walker = {
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name: key,
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type: false,
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nullable: false
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};
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if (!Array.isArray(structure[key])) {
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fieldTypes = [structure[key]];
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}
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for (var i = 0; i < fieldTypes.length; i++) {
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var fieldType = fieldTypes[i];
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if (fieldType === null) {
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walker.nullable = true;
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} else if (typeof fieldType === 'string') {
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walker.type = 'node';
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} else if (Array.isArray(fieldType)) {
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walker.type = 'list';
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}
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}
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if (walker.type) {
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walkers.push(walker);
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}
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}
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if (walkers.length) {
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return {
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context: nodeType.walkContext,
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fields: walkers
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};
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}
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return null;
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}
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function getTypesFromConfig(config) {
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var types = {};
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for (var name in config.node) {
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if (hasOwnProperty.call(config.node, name)) {
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var nodeType = config.node[name];
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if (!nodeType.structure) {
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throw new Error('Missed `structure` field in `' + name + '` node type definition');
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}
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types[name] = getWalkersFromStructure(name, nodeType);
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}
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}
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return types;
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}
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function createTypeIterator(config, reverse) {
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var fields = config.fields.slice();
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var contextName = config.context;
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var useContext = typeof contextName === 'string';
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if (reverse) {
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fields.reverse();
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}
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return function(node, context, walk) {
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var prevContextValue;
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if (useContext) {
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prevContextValue = context[contextName];
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context[contextName] = node;
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}
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for (var i = 0; i < fields.length; i++) {
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var field = fields[i];
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var ref = node[field.name];
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if (!field.nullable || ref) {
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if (field.type === 'list') {
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if (reverse) {
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ref.forEachRight(walk);
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} else {
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ref.forEach(walk);
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}
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} else {
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walk(ref);
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}
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}
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}
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if (useContext) {
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context[contextName] = prevContextValue;
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}
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};
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}
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function createFastTraveralMap(iterators) {
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return {
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Atrule: {
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StyleSheet: iterators.StyleSheet,
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Atrule: iterators.Atrule,
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Rule: iterators.Rule,
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Block: iterators.Block
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},
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Rule: {
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StyleSheet: iterators.StyleSheet,
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Atrule: iterators.Atrule,
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Rule: iterators.Rule,
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Block: iterators.Block
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},
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Declaration: {
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StyleSheet: iterators.StyleSheet,
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Atrule: iterators.Atrule,
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Rule: iterators.Rule,
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Block: iterators.Block
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}
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};
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}
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module.exports = function createWalker(config) {
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var types = getTypesFromConfig(config);
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var iteratorsNatural = {};
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var iteratorsReverse = {};
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for (var name in types) {
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if (hasOwnProperty.call(types, name) && types[name] !== null) {
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iteratorsNatural[name] = createTypeIterator(types[name], false);
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iteratorsReverse[name] = createTypeIterator(types[name], true);
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}
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}
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var fastTraversalIteratorsNatural = createFastTraveralMap(iteratorsNatural);
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var fastTraversalIteratorsReverse = createFastTraveralMap(iteratorsReverse);
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var walk = function(root, options) {
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function walkNode(node, item, list) {
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enter.call(context, node, item, list);
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if (iterators.hasOwnProperty(node.type)) {
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iterators[node.type](node, context, walkNode);
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}
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leave.call(context, node, item, list);
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}
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var enter = noop;
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var leave = noop;
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var iterators = iteratorsNatural;
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var context = {
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root: root,
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stylesheet: null,
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atrule: null,
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atrulePrelude: null,
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rule: null,
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selector: null,
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block: null,
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declaration: null,
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function: null
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};
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if (typeof options === 'function') {
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enter = options;
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} else if (options) {
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enter = ensureFunction(options.enter);
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leave = ensureFunction(options.leave);
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if (options.reverse) {
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iterators = iteratorsReverse;
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}
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if (options.visit) {
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if (fastTraversalIteratorsNatural.hasOwnProperty(options.visit)) {
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iterators = options.reverse
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? fastTraversalIteratorsReverse[options.visit]
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: fastTraversalIteratorsNatural[options.visit];
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} else if (!types.hasOwnProperty(options.visit)) {
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throw new Error('Bad value `' + options.visit + '` for `visit` option (should be: ' + Object.keys(types).join(', ') + ')');
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}
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enter = invokeForType(enter, options.visit);
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leave = invokeForType(leave, options.visit);
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}
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}
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if (enter === noop && leave === noop) {
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throw new Error('Neither `enter` nor `leave` walker handler is set or both aren\'t a function');
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}
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// swap handlers in reverse mode to invert visit order
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if (options.reverse) {
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var tmp = enter;
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enter = leave;
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leave = tmp;
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}
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walkNode(root);
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};
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walk.find = function(ast, fn) {
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var found = null;
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walk(ast, function(node, item, list) {
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if (found === null && fn.call(this, node, item, list)) {
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found = node;
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}
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});
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return found;
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};
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walk.findLast = function(ast, fn) {
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var found = null;
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walk(ast, {
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reverse: true,
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enter: function(node, item, list) {
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if (found === null && fn.call(this, node, item, list)) {
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found = node;
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}
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}
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});
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return found;
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};
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walk.findAll = function(ast, fn) {
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var found = [];
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walk(ast, function(node, item, list) {
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if (fn.call(this, node, item, list)) {
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found.push(node);
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}
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});
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return found;
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};
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return walk;
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};
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