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95 lines
2.1 KiB
95 lines
2.1 KiB
2 years ago
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'use strict';
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const OVERRIDABLE_RULES = new Set(['keyframes', 'counter-style']);
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const SCOPE_RULES = new Set(['media', 'supports']);
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/**
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* @param {string} prop
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* @return {string}
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*/
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function vendorUnprefixed(prop) {
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return prop.replace(/^-\w+-/, '');
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}
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/**
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* @param {string} name
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* @return {boolean}
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*/
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function isOverridable(name) {
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return OVERRIDABLE_RULES.has(vendorUnprefixed(name.toLowerCase()));
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}
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/**
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* @param {string} name
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* @return {boolean}
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*/
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function isScope(name) {
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return SCOPE_RULES.has(vendorUnprefixed(name.toLowerCase()));
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}
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/**
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* @param {import('postcss').AtRule} node
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* @return {string}
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*/
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function getScope(node) {
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/** @type {import('postcss').Container<import('postcss').ChildNode> | import('postcss').Document | undefined} */
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let current = node.parent;
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const chain = [node.name.toLowerCase(), node.params];
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while (current) {
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if (
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current.type === 'atrule' &&
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isScope(/** @type import('postcss').AtRule */ (current).name)
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) {
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chain.unshift(
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/** @type import('postcss').AtRule */ (current).name +
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' ' +
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/** @type import('postcss').AtRule */ (current).params
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);
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}
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current = current.parent;
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}
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return chain.join('|');
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}
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/**
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* @type {import('postcss').PluginCreator<void>}
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* @return {import('postcss').Plugin}
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*/
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function pluginCreator() {
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return {
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postcssPlugin: 'postcss-discard-overridden',
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prepare() {
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const cache = new Map();
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/** @type {{node: import('postcss').AtRule, scope: string}[]} */
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const rules = [];
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return {
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OnceExit(css) {
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css.walkAtRules((node) => {
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if (isOverridable(node.name)) {
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const scope = getScope(node);
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cache.set(scope, node);
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rules.push({
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node,
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scope,
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});
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}
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});
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rules.forEach((rule) => {
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if (cache.get(rule.scope) !== rule.node) {
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rule.node.remove();
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}
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});
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},
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};
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},
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};
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}
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pluginCreator.postcss = true;
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module.exports = pluginCreator;
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