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53 lines
1.2 KiB
53 lines
1.2 KiB
4 years ago
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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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module.exports = function(node, options, context) {
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function walk(node) {
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enter.call(context, node);
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switch (node.type) {
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case 'Group':
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node.terms.forEach(walk);
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break;
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case 'Multiplier':
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walk(node.term);
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break;
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case 'Type':
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case 'Property':
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case 'Keyword':
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case 'AtKeyword':
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case 'Function':
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case 'String':
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case 'Token':
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case 'Comma':
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break;
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default:
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throw new Error('Unknown type: ' + node.type);
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}
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leave.call(context, node);
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}
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var enter = noop;
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var leave = noop;
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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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}
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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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walk(node, context);
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};
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