Add support for PostCSS 8

Closes postcss#147.

.gitignore

@@ -1,4 +1,5 @@
 node_modules
 test/fixtures/*.actual.css
 test/fixtures/build
+test/fixtures/test
 .idea

README.md

@@ -10,7 +10,7 @@
 ## Installation
 
 ```console
-$ npm install postcss-url
+$ npm install postcss postcss-url
 ```
 
 ## Basic example - rebase

package.json

@@ -26,16 +26,19 @@
     "mime": "2.3.1",
     "minimatch": "3.0.4",
     "mkdirp": "0.5.0",
-    "postcss": "7.0.2",
     "xxhashjs": "0.2.1"
   },
   "devDependencies": {
     "chai": "4.1.2",
     "eslint": "5.16.0",
     "mocha": "5.2.0",
     "npmpub": "4.1.0",
+    "postcss": "8.1.2",
     "postcss-import": "12.0.0"
   },
+  "peerDependencies": {
+    "postcss": "8.1.2"
+  },
   "scripts": {
     "lint": "eslint --fix .",
     "tests": "mocha",

src/index.js

@@ -1,30 +1,32 @@
 'use strict';
 
 const path = require('path');
-const postcss = require('postcss');
 
 const declProcessor = require('./lib/decl-processor').declProcessor;
 
-/**
- *
- * @type {Plugin}
- */
-module.exports = postcss.plugin('postcss-url', (options) => {
+const plugin = (options) => {
     options = options || {};
 
-    return function(styles, result) {
-        const promises = [];
-        const opts = result.opts;
-        const from = opts.from ? path.dirname(opts.from) : '.';
-        const to = opts.to ? path.dirname(opts.to) : from;
+    return {
+        postcssPlugin: 'postcss-url',
+        Once(styles, { result }) {
+            const promises = [];
+            const opts = result.opts;
+            const from = opts.from ? path.dirname(opts.from) : '.';
+            const to = opts.to ? path.dirname(opts.to) : from;
 
-        styles.walkDecls((decl) =>
-            promises.push(declProcessor(from, to, options, result, decl))
-        );
+            styles.walkDecls((decl) =>
+                promises.push(declProcessor(from, to, options, result, decl))
+            );
 
-        return Promise.all(promises);
+            return Promise.all(promises);
+        }
     };
-});
+};
+
+plugin.postcss = true;
+
+module.exports = plugin;
 
 /**
  * @callback PostcssUrl~UrlProcessor

test/setup.js

@@ -13,15 +13,15 @@ global.postcssUrl = url;
 function compareFixtures(name, msg, opts, postcssOpts, plugin) {
     it(msg, () => {
         opts = opts || {};
-        const pcss = postcss();
+        const plugins = [];
 
         if (plugin) {
-            pcss.use(plugin());
+            plugins.push(plugin());
         }
 
-        pcss.use(url(opts));
+        plugins.push(url(opts));
 
-        return pcss.process(read(`fixtures/${name}`), postcssOpts)
+        return postcss(plugins).process(read(`fixtures/${name}`), postcssOpts)
             .then((result) => {
                 const actual = result.css;
                 const expected = read(`fixtures/${name}.expected`);