feat(lib): initial development

develop/index.js

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+const fs = require('fs');
+const path = require('path');
+const postcss = require('postcss');
+const plugin = require('../lib');
+
+const fixturePath = path.join(process.cwd(), 'tests', 'fixtures');
+const read = (file) => fs.readFileSync(path.join(fixturePath, file), 'utf-8');
+const input = read('develop.css');
+
+postcss()
+	.use(plugin)
+	.process(input, { from: undefined, to: undefined })
+	.then((result) => {
+		console.log(result.css);
+	})
+	.catch(console.error);

lib/index.js

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+'use strict';
+
+const postcss = require('postcss');
+
+module.exports = postcss.plugin('postcss-selector-scope', (options = {}) => {
+	options = Object.assign({
+		not: '.style-scope',
+		exclude: [':root']
+	}, options);
+
+	const excluded = (options.exclude || []).join('|');
+	const included = new RegExp(`^(?!${excluded})\\S+`);
+
+	const scope = (pattern) => (str) => {
+		const result = str.match(pattern) ? `${str}:not(${options.not})` : str;
+
+		return result;
+	};
+
+	const transform = (pattern) => (selector) => selector.split(' ').map(scope(pattern)).join(' ');
+
+	return (root) => {
+		root.walkRules((rule) => {
+			rule.selectors = rule.selectors.map(transform(included));
+		});
+	};
+});

tests/fixtures/develop.css

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+/* excluded */
+:root {
+  --some-var: red;
+}
+
+/* tags */
+a,
+b,
+strong,
+html,
+body,
+body .class,
+.class div {
+    color: red;
+}
+
+/* classes and IDs */
+.foo,
+#bar,
+#id .class,
+.class #id {
+    color: red;
+}
+
+/* pseudo and not */
+div::after,
+div:after {
+  content: "";
+}
+
+a:hover,
+::selection,
+:focus {
+  outline: 1px solid blue;
+}
+
+.any:not(.selected) {
+  color: red;
+}
+
+/* attributes */
+[class*="any"],
+[class^="any-"],
+[class*=" any"] {
+  color: red;
+}