113 lines
2.8 KiB
JavaScript
113 lines
2.8 KiB
JavaScript
/**
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* The MIT License (MIT)
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* Copyright (c) 2017-present Dmitry Soshnikov <[email protected]>
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*/
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'use strict';
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var _require = require('../../transform/utils'),
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increaseQuantifierByOne = _require.increaseQuantifierByOne;
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/**
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* A regexp-tree plugin to merge quantifiers
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*
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* a+a+ -> a{2,}
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* a{2}a{3} -> a{5}
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* a{1,2}a{2,3} -> a{3,5}
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*/
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module.exports = {
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Repetition: function Repetition(path) {
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var node = path.node,
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parent = path.parent;
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if (parent.type !== 'Alternative' || !path.index) {
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return;
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}
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var previousSibling = path.getPreviousSibling();
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if (!previousSibling) {
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return;
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}
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if (previousSibling.node.type === 'Repetition') {
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if (!previousSibling.getChild().hasEqualSource(path.getChild())) {
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return;
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}
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var _extractFromTo = extractFromTo(previousSibling.node.quantifier),
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previousSiblingFrom = _extractFromTo.from,
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previousSiblingTo = _extractFromTo.to;
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var _extractFromTo2 = extractFromTo(node.quantifier),
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nodeFrom = _extractFromTo2.from,
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nodeTo = _extractFromTo2.to;
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// It's does not seem reliable to merge quantifiers with different greediness
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// when none of both is a greedy open range
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if (previousSibling.node.quantifier.greedy !== node.quantifier.greedy && !isGreedyOpenRange(previousSibling.node.quantifier) && !isGreedyOpenRange(node.quantifier)) {
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return;
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}
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// a*a* -> a*
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// a*a+ -> a+
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// a+a+ -> a{2,}
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// a{2}a{4} -> a{6}
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// a{1,2}a{2,3} -> a{3,5}
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// a{1,}a{2,} -> a{3,}
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// a+a{2,} -> a{3,}
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// a??a{2,} -> a{2,}
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// a*?a{2,} -> a{2,}
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// a+?a{2,} -> a{3,}
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node.quantifier.kind = 'Range';
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node.quantifier.from = previousSiblingFrom + nodeFrom;
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if (previousSiblingTo && nodeTo) {
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node.quantifier.to = previousSiblingTo + nodeTo;
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} else {
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delete node.quantifier.to;
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}
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if (isGreedyOpenRange(previousSibling.node.quantifier) || isGreedyOpenRange(node.quantifier)) {
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node.quantifier.greedy = true;
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}
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previousSibling.remove();
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} else {
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if (!previousSibling.hasEqualSource(path.getChild())) {
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return;
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}
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increaseQuantifierByOne(node.quantifier);
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previousSibling.remove();
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}
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}
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};
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function isGreedyOpenRange(quantifier) {
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return quantifier.greedy && (quantifier.kind === '+' || quantifier.kind === '*' || quantifier.kind === 'Range' && !quantifier.to);
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}
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function extractFromTo(quantifier) {
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var from = void 0,
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to = void 0;
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if (quantifier.kind === '*') {
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from = 0;
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} else if (quantifier.kind === '+') {
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from = 1;
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} else if (quantifier.kind === '?') {
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from = 0;
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to = 1;
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} else {
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from = quantifier.from;
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if (quantifier.to) {
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to = quantifier.to;
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}
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}
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return { from: from, to: to };
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} |