48 lines
1.6 KiB
JavaScript
48 lines
1.6 KiB
JavaScript
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// vue compiler module for transforming `img:srcset` to a number of `require`s
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const urlToRequire = require('../url-to-require')
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module.exports = () => ({
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postTransformNode: node => {
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transform(node)
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}
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})
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function transform (node) {
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const tags = ['img', 'source']
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if (tags.indexOf(node.tag) !== -1 && node.attrs) {
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node.attrs.forEach(attr => {
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if (attr.name === 'srcset') {
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// same logic as in transform-require.js
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const value = attr.value
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const isStatic = value.charAt(0) === '"' && value.charAt(value.length - 1) === '"'
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if (!isStatic) {
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return
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}
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// http://w3c.github.io/html/semantics-embedded-content.html#ref-for-image-candidate-string-5
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const escapedSpaceCharacters = /( |\\t|\\n|\\f|\\r)+/g
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const imageCandidates = value.substr(1, value.length - 2).split(',').map(s => {
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// The attribute value arrives here with all whitespace, except normal spaces, represented by escape sequences
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const [url, descriptor] = s.replace(escapedSpaceCharacters, ' ').trim().split(' ', 2)
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return { require: urlToRequire(url), descriptor: descriptor }
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})
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// "require(url1)"
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// "require(url1) 1x"
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// "require(url1), require(url2)"
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// "require(url1), require(url2) 2x"
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// "require(url1) 1x, require(url2)"
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// "require(url1) 1x, require(url2) 2x"
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const code = imageCandidates.map(
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({ require, descriptor }) => `${require} + "${descriptor ? ' ' + descriptor : ''}, " + `
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).join('').slice(0, -6).concat('"').replace(/ \+ ""$/, '')
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attr.value = code
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}
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})
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}
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}
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