const visit = require('unist-util-visit'); const is = require('hast-util-is-element'); const source = require('unist-util-source'); /** * Add the width and height of the image to the `img` tag if they are * not already provided. This helps prevent jank when the page is * rendered before the image has downloaded. * * If there is no `src` attribute on an image, or it is not possible * to load the image file indicated by the `src` then a warning is emitted. */ module.exports = function addImageDimensions(getImageDimensions) { return function addImageDimensionsImpl() { return (ast, file) => { visit(ast, node => { if (is(node, 'img')) { const props = node.properties; const src = props.src; if (!src) { file.message('Missing src in image tag `' + source(node, file) + '`'); } else { try { const dimensions = getImageDimensions(addImageDimensionsImpl.basePath, src); if (props.width === undefined && props.height === undefined) { props.width = '' + dimensions.width; props.height = '' + dimensions.height; } } catch(e) { if (e.code === 'ENOENT') { file.fail('Unable to load src in image tag `' + source(node, file) + '`'); } else { file.fail(e.message); } } } } }); }; }; };