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inlineStyles.js
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Tue, Feb 11, 08:34

inlineStyles.js
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'use strict';
/**
* @typedef {import('../lib/types').Specificity} Specificity
* @typedef {import('../lib/types').XastElement} XastElement
* @typedef {import('../lib/types').XastParent} XastParent
*/
const csstree = require('css-tree');
// @ts-ignore not defined in @types/csso
const specificity = require('csso/lib/restructure/prepare/specificity');
const stable = require('stable');
const {
visitSkip,
querySelectorAll,
detachNodeFromParent,
} = require('../lib/xast.js');
exports.type = 'visitor';
exports.name = 'inlineStyles';
exports.active = true;
exports.description = 'inline styles (additional options)';
/**
* Compares two selector specificities.
* extracted from https://github.com/keeganstreet/specificity/blob/master/specificity.js#L211
*
* @type {(a: Specificity, b: Specificity) => number}
*/
const compareSpecificity = (a, b) => {
for (var i = 0; i < 4; i += 1) {
if (a[i] < b[i]) {
return -1;
} else if (a[i] > b[i]) {
return 1;
}
}
return 0;
};
/**
* Moves + merges styles from style elements to element styles
*
* Options
* onlyMatchedOnce (default: true)
* inline only selectors that match once
*
* removeMatchedSelectors (default: true)
* clean up matched selectors,
* leave selectors that hadn't matched
*
* useMqs (default: ['', 'screen'])
* what media queries to be used
* empty string element for styles outside media queries
*
* usePseudos (default: [''])
* what pseudo-classes/-elements to be used
* empty string element for all non-pseudo-classes and/or -elements
*
* @author strarsis <strarsis@gmail.com>
*
* @type {import('../lib/types').Plugin<{
* onlyMatchedOnce?: boolean,
* removeMatchedSelectors?: boolean,
* useMqs?: Array<string>,
* usePseudos?: Array<string>
* }>}
*/
exports.fn = (root, params) => {
const {
onlyMatchedOnce = true,
removeMatchedSelectors = true,
useMqs = ['', 'screen'],
usePseudos = [''],
} = params;
/**
* @type {Array<{ node: XastElement, parentNode: XastParent, cssAst: csstree.StyleSheet }>}
*/
const styles = [];
/**
* @type {Array<{
* node: csstree.Selector,
* item: csstree.ListItem<csstree.CssNode>,
* rule: csstree.Rule,
* matchedElements?: Array<XastElement>
* }>}
*/
let selectors = [];
return {
element: {
enter: (node, parentNode) => {
// skip <foreignObject /> content
if (node.name === 'foreignObject') {
return visitSkip;
}
// collect only non-empty <style /> elements
if (node.name !== 'style' || node.children.length === 0) {
return;
}
// values other than the empty string or text/css are not used
if (
node.attributes.type != null &&
node.attributes.type !== '' &&
node.attributes.type !== 'text/css'
) {
return;
}
// parse css in style element
let cssText = '';
for (const child of node.children) {
if (child.type === 'text' || child.type === 'cdata') {
cssText += child.value;
}
}
/**
* @type {null | csstree.CssNode}
*/
let cssAst = null;
try {
cssAst = csstree.parse(cssText, {
parseValue: false,
parseCustomProperty: false,
});
} catch {
return;
}
if (cssAst.type === 'StyleSheet') {
styles.push({ node, parentNode, cssAst });
}
// collect selectors
csstree.walk(cssAst, {
visit: 'Selector',
enter(node, item) {
const atrule = this.atrule;
const rule = this.rule;
if (rule == null) {
return;
}
// skip media queries not included into useMqs param
let mq = '';
if (atrule != null) {
mq = atrule.name;
if (atrule.prelude != null) {
mq += ` ${csstree.generate(atrule.prelude)}`;
}
}
if (useMqs.includes(mq) === false) {
return;
}
/**
* @type {Array<{
* item: csstree.ListItem<csstree.CssNode>,
* list: csstree.List<csstree.CssNode>
* }>}
*/
const pseudos = [];
if (node.type === 'Selector') {
node.children.each((childNode, childItem, childList) => {
if (
childNode.type === 'PseudoClassSelector' ||
childNode.type === 'PseudoElementSelector'
) {
pseudos.push({ item: childItem, list: childList });
}
});
}
// skip pseudo classes and pseudo elements not includes into usePseudos param
const pseudoSelectors = csstree.generate({
type: 'Selector',
children: new csstree.List().fromArray(
pseudos.map((pseudo) => pseudo.item.data)
),
});
if (usePseudos.includes(pseudoSelectors) === false) {
return;
}
// remove pseudo classes and elements to allow querySelector match elements
// TODO this is not very accurate since some pseudo classes like first-child
// are used for selection
for (const pseudo of pseudos) {
pseudo.list.remove(pseudo.item);
}
selectors.push({ node, item, rule });
},
});
},
},
root: {
exit: () => {
if (styles.length === 0) {
return;
}
// stable sort selectors
const sortedSelectors = stable(selectors, (a, b) => {
const aSpecificity = specificity(a.item.data);
const bSpecificity = specificity(b.item.data);
return compareSpecificity(aSpecificity, bSpecificity);
}).reverse();
for (const selector of sortedSelectors) {
// match selectors
const selectorText = csstree.generate(selector.item.data);
/**
* @type {Array<XastElement>}
*/
const matchedElements = [];
try {
for (const node of querySelectorAll(root, selectorText)) {
if (node.type === 'element') {
matchedElements.push(node);
}
}
} catch (selectError) {
continue;
}
// nothing selected
if (matchedElements.length === 0) {
continue;
}
// apply styles to matched elements
// skip selectors that match more than once if option onlyMatchedOnce is enabled
if (onlyMatchedOnce && matchedElements.length > 1) {
continue;
}
// apply <style/> to matched elements
for (const selectedEl of matchedElements) {
const styleDeclarationList = csstree.parse(
selectedEl.attributes.style == null
? ''
: selectedEl.attributes.style,
{
context: 'declarationList',
parseValue: false,
}
);
if (styleDeclarationList.type !== 'DeclarationList') {
continue;
}
const styleDeclarationItems = new Map();
csstree.walk(styleDeclarationList, {
visit: 'Declaration',
enter(node, item) {
styleDeclarationItems.set(node.property, item);
},
});
// merge declarations
csstree.walk(selector.rule, {
visit: 'Declaration',
enter(ruleDeclaration) {
// existing inline styles have higher priority
// no inline styles, external styles, external styles used
// inline styles, external styles same priority as inline styles, inline styles used
// inline styles, external styles higher priority than inline styles, external styles used
const matchedItem = styleDeclarationItems.get(
ruleDeclaration.property
);
const ruleDeclarationItem =
styleDeclarationList.children.createItem(ruleDeclaration);
if (matchedItem == null) {
styleDeclarationList.children.append(ruleDeclarationItem);
} else if (
matchedItem.data.important !== true &&
ruleDeclaration.important === true
) {
styleDeclarationList.children.replace(
matchedItem,
ruleDeclarationItem
);
styleDeclarationItems.set(
ruleDeclaration.property,
ruleDeclarationItem
);
}
},
});
selectedEl.attributes.style =
csstree.generate(styleDeclarationList);
}
if (
removeMatchedSelectors &&
matchedElements.length !== 0 &&
selector.rule.prelude.type === 'SelectorList'
) {
// clean up matching simple selectors if option removeMatchedSelectors is enabled
selector.rule.prelude.children.remove(selector.item);
}
selector.matchedElements = matchedElements;
}
// no further processing required
if (removeMatchedSelectors === false) {
return;
}
// clean up matched class + ID attribute values
for (const selector of sortedSelectors) {
if (selector.matchedElements == null) {
continue;
}
if (onlyMatchedOnce && selector.matchedElements.length > 1) {
// skip selectors that match more than once if option onlyMatchedOnce is enabled
continue;
}
for (const selectedEl of selector.matchedElements) {
// class
const classList = new Set(
selectedEl.attributes.class == null
? null
: selectedEl.attributes.class.split(' ')
);
const firstSubSelector = selector.node.children.first();
if (
firstSubSelector != null &&
firstSubSelector.type === 'ClassSelector'
) {
classList.delete(firstSubSelector.name);
}
if (classList.size === 0) {
delete selectedEl.attributes.class;
} else {
selectedEl.attributes.class = Array.from(classList).join(' ');
}
// ID
if (
firstSubSelector != null &&
firstSubSelector.type === 'IdSelector'
) {
if (selectedEl.attributes.id === firstSubSelector.name) {
delete selectedEl.attributes.id;
}
}
}
}
for (const style of styles) {
csstree.walk(style.cssAst, {
visit: 'Rule',
enter: function (node, item, list) {
// clean up <style/> rulesets without any css selectors left
if (
node.type === 'Rule' &&
node.prelude.type === 'SelectorList' &&
node.prelude.children.isEmpty()
) {
list.remove(item);
}
},
});
if (style.cssAst.children.isEmpty()) {
// remove emtpy style element
detachNodeFromParent(style.node, style.parentNode);
} else {
// update style element if any styles left
const firstChild = style.node.children[0];
if (firstChild.type === 'text' || firstChild.type === 'cdata') {
firstChild.value = csstree.generate(style.cssAst);
}
}
}
},
},
};
};

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