postcss-url-parser.js

import { promisify } from 'util';

import postcss from 'postcss';
import valueParser from 'postcss-value-parser';

import {
  normalizeUrl,
  requestify,
  resolveRequests,
  isUrlRequestable,
} from '../utils';

const pluginName = 'postcss-url-parser';

const isUrlFunc = /url/i;
const isImageSetFunc = /^(?:-webkit-)?image-set$/i;
const needParseDecl = /(?:url|(?:-webkit-)?image-set)\(/i;

function getNodeFromUrlFunc(node) {
  return node.nodes && node.nodes[0];
}

function shouldHandleRule(rule, decl, result) {
  // https://www.w3.org/TR/css-syntax-3/#typedef-url-token
  if (rule.url.replace(/^[\s]+|[\s]+$/g, '').length === 0) {
    result.warn(`Unable to find uri in '${decl.toString()}'`, { node: decl });

    return false;
  }

  if (!isUrlRequestable(rule.url)) {
    return false;
  }

  return true;
}

function walkCss(css, result, options, callback) {
  const accumulator = [];

  css.walkDecls((decl) => {
    if (!needParseDecl.test(decl.value)) {
      return;
    }

    const parsed = valueParser(decl.value);

    parsed.walk((node) => {
      if (node.type !== 'function') {
        return;
      }

      if (isUrlFunc.test(node.value)) {
        const { nodes } = node;
        const isStringValue = nodes.length !== 0 && nodes[0].type === 'string';
        const url = isStringValue
          ? nodes[0].value
          : valueParser.stringify(nodes);

        const rule = {
          node: getNodeFromUrlFunc(node),
          url,
          needQuotes: false,
          isStringValue,
        };

        if (shouldHandleRule(rule, decl, result)) {
          accumulator.push({ decl, rule, parsed });
        }

        // Do not traverse inside `url`
        // eslint-disable-next-line consistent-return
        return false;
      } else if (isImageSetFunc.test(node.value)) {
        for (const nNode of node.nodes) {
          const { type, value } = nNode;

          if (type === 'function' && isUrlFunc.test(value)) {
            const { nodes } = nNode;
            const isStringValue =
              nodes.length !== 0 && nodes[0].type === 'string';
            const url = isStringValue
              ? nodes[0].value
              : valueParser.stringify(nodes);

            const rule = {
              node: getNodeFromUrlFunc(nNode),
              url,
              needQuotes: false,
              isStringValue,
            };

            if (shouldHandleRule(rule, decl, result)) {
              accumulator.push({ decl, rule, parsed });
            }
          } else if (type === 'string') {
            const rule = {
              node: nNode,
              url: value,
              needQuotes: true,
              isStringValue: true,
            };

            if (shouldHandleRule(rule, decl, result)) {
              accumulator.push({ decl, rule, parsed });
            }
          }
        }

        // Do not traverse inside `image-set`
        // eslint-disable-next-line consistent-return
        return false;
      }
    });
  });

  callback(null, accumulator);
}

const asyncWalkCss = promisify(walkCss);

export default postcss.plugin(pluginName, (options) => async (css, result) => {
  const parsedResults = await asyncWalkCss(css, result, options);

  if (parsedResults.length === 0) {
    return Promise.resolve();
  }

  const tasks = [];
  const imports = new Map();
  const replacements = new Map();

  let hasUrlImportHelper = false;

  for (const parsedResult of parsedResults) {
    const { url, isStringValue } = parsedResult.rule;

    let normalizedUrl = url;
    let prefix = '';

    const queryParts = normalizedUrl.split('!');

    if (queryParts.length > 1) {
      normalizedUrl = queryParts.pop();
      prefix = queryParts.join('!');
    }

    normalizedUrl = normalizeUrl(normalizedUrl, isStringValue);

    if (!options.filter(normalizedUrl)) {
      // eslint-disable-next-line no-continue
      continue;
    }

    if (!hasUrlImportHelper) {
      options.imports.push({
        importName: '___CSS_LOADER_GET_URL_IMPORT___',
        url: options.urlHandler(require.resolve('../runtime/getUrl.js')),
        index: -1,
      });

      hasUrlImportHelper = true;
    }

    const splittedUrl = normalizedUrl.split(/(\?)?#/);
    const [pathname, query, hashOrQuery] = splittedUrl;

    let hash = query ? '?' : '';
    hash += hashOrQuery ? `#${hashOrQuery}` : '';

    const request = requestify(pathname, options.rootContext);

    tasks.push(
      (async () => {
        const { resolver, context } = options;
        const resolvedUrl = await resolveRequests(resolver, context, [
          ...new Set([request, normalizedUrl]),
        ]);

        return { url: resolvedUrl, prefix, hash, parsedResult };
      })()
    );
  }

  const results = await Promise.all(tasks);

  for (let index = 0; index <= results.length - 1; index++) {
    const {
      url,
      prefix,
      hash,
      parsedResult: { decl, rule, parsed },
    } = results[index];
    const newUrl = prefix ? `${prefix}!${url}` : url;
    const importKey = newUrl;
    let importName = imports.get(importKey);

    if (!importName) {
      importName = `___CSS_LOADER_URL_IMPORT_${imports.size}___`;
      imports.set(importKey, importName);

      options.imports.push({
        importName,
        url: options.urlHandler(newUrl),
        index,
      });
    }

    const { needQuotes } = rule;
    const replacementKey = JSON.stringify({ newUrl, hash, needQuotes });
    let replacementName = replacements.get(replacementKey);

    if (!replacementName) {
      replacementName = `___CSS_LOADER_URL_REPLACEMENT_${replacements.size}___`;
      replacements.set(replacementKey, replacementName);

      options.replacements.push({
        replacementName,
        importName,
        hash,
        needQuotes,
      });
    }

    // eslint-disable-next-line no-param-reassign
    rule.node.type = 'word';
    // eslint-disable-next-line no-param-reassign
    rule.node.value = replacementName;

    // eslint-disable-next-line no-param-reassign
    decl.value = parsed.toString();
  }

  return Promise.resolve();
});