index.js

const postcss = require('postcss');

module.exports = postcss.plugin('postcss-comment-annotation', (opts) => {
    opts = opts || {};

    const prefix = opts.prefix || '@';
    const newLine = '(?:\\r?\\n|.)*?)';
    const matchComment = `(\\${prefix}${newLine}(?=\\${prefix}|$)`;
    const matchKeyVal = `\\${prefix}(\\w*)\\s(${newLine}(?=\\r?\\n\\r?\\n|$)`;
    const matchBool = `\\${prefix}(\\w+)\\s*(?=\\n|$)`;

    return (root, result) => {
        result.commentAnnotations = [];

        root.walkComments((comment) => {
            const annotationArray = comment.text.match(
                new RegExp(matchComment, 'g')
            );
            const annotationObj = {};

            if (annotationArray) {
                annotationArray.forEach((annotation) => {
                    // Match @rule with single or multiline value after it
                    if (annotation.match(new RegExp(matchKeyVal, 'g')) &&
                      RegExp.$2 !== '\n') {
                        const key = RegExp.$1;
                        const val = RegExp.$2;

                        val.replace(/^\s/g, '');

                        // Create key:value pair
                        annotationObj[key] = val;
                    }

                    // Match single @rule and treat as true
                    if (annotation.match(new RegExp(matchBool, 'g'))) {
                        const key = RegExp.$1;
                        annotationObj[key] = annotationObj[key] || true;
                    }
                });

                if (Object.getOwnPropertyNames(annotationObj).length !== 0) {
                    annotationObj.type = 'comment-annotation';
                    annotationObj.plugin = 'comment-annotation';
                    result.commentAnnotations.push(annotationObj);
                }
            }
        });
    };
});