support postcss 8 plugins, closes #5

.travis.yml

@@ -8,9 +8,21 @@ os:
   - osx
 
 node_js:
+  - 14
   - 12
   - 10
-  - 8
+
+jobs:
+  include:
+    - node_js: 8
+      os: windows
+      before_script: |
+        npm install postcss@7
+        nvs add 12
+        nvs use 12
+        npm run pretest:tape
+        nvs use 8
+      script: npm run test:tape:7 -- --ci true
 
 install:
   - git config --global core.autocrlf false

package.json

@@ -21,20 +21,25 @@
     "pretest:tape": "npm run build",
     "test": "npm run test:js && npm run test:tape",
     "test:js": "eslint src/{*,**/*}.js --cache --ignore-pattern .gitignore",
-    "test:tape": "node . --plugin test/plugin.js --config test",
-    "test:tape:ci": "node . --ci true --plugin test/plugin.js --config test"
+    "test:tape:7": "node . --plugin test/postcss7-plugin.js --config test",
+    "test:tape:8": "node . --plugin test/postcss8-plugin.js --config test",
+    "test:tape": "npm run test:tape:7 && npm run test:tape:8",
+    "test:tape:ci": "npm run test:tape:7 -- --ci true && npm run test:tape:8 -- --ci true"
   },
   "engines": {
     "node": ">=8.0.0"
   },
+  "peerDependencies": {
+    "postcss": "^7.0.0 || ^8.0.0"
+  },
   "devDependencies": {
     "@babel/core": "^7.7.2",
     "@babel/plugin-syntax-dynamic-import": "^7.2.0",
     "@babel/preset-env": "^7.7.1",
     "babel-eslint": "^10.0.3",
     "eslint": "^6.6.0",
-    "postcss": "^7.0.21",
-    "rollup": "^1.26.3",
+    "postcss": "^8.0.5",
+    "rollup": "^2.27.1",
     "rollup-plugin-babel": "^4.3.3",
     "rollup-plugin-terser": "^5.1.2"
   },

src/index.js

@@ -5,6 +5,20 @@ import getErrorMessage from './lib/get-error-message';
 import getOptions from './lib/get-options';
 import path from 'path';
 
+async function postcss8(plugins) {
+	const pkg = await import('postcss/package.json');
+	if (pkg.version[0] === '8') {
+		const m = await import('postcss');
+		return m.default(plugins);
+	} else {
+		throw new Error(`postcss@8 must be installed, found ${pkg.version}`);
+	}
+}
+
+function isPostcss8Plugin(plugin) {
+	return typeof plugin === 'function' && Object(plugin).postcss === true;
+}
+
 getOptions().then(
 	async options => {
 		let hadError = false;
@@ -13,12 +27,6 @@ getOptions().then(
 		for (const name in options.config) {
 			const test = options.config[name];
 
-			const testPlugin = typeof Object(test.plugin).process === 'function'
-				? test.plugin
-			: typeof test.plugin === 'function'
-				? { process: test.plugin }
-			: options.plugin;
-
 			const testBase = name.split(':')[0];
 			const testFull = name.split(':').join('.');
 
@@ -30,7 +38,19 @@ getOptions().then(
 			const processOptions = Object.assign({ from: sourcePath, to: resultPath }, test.processOptions);
 			const pluginOptions = test.options;
 
-			const pluginName = Object(testPlugin.postcss).postcssPlugin || 'postcss';
+			let rawPlugin = test.plugin || options.plugin;
+			if (rawPlugin.default) {
+				rawPlugin = rawPlugin.default;
+			}
+			const plugin = isPostcss8Plugin(rawPlugin)
+				? rawPlugin(pluginOptions)
+			: typeof Object(rawPlugin).process === 'function'
+				? rawPlugin
+			: typeof rawPlugin === 'function'
+				? { process: rawPlugin }
+			: Object(rawPlugin).postcssPlugin;
+
+			const pluginName = plugin.postcssPlugin || Object(rawPlugin.postcss).postcssPlugin || 'postcss';
 
 			log.wait(pluginName, test.message, options.ci);
 
@@ -42,7 +62,13 @@ getOptions().then(
 				const expectCSS = await safelyReadFile(expectPath);
 				const sourceCSS = await readOrWriteFile(sourcePath, expectCSS);
 
-				const result = await testPlugin.process(sourceCSS, processOptions, pluginOptions);
+				let result;
+				if (isPostcss8Plugin(rawPlugin)) {
+					const postcss = await postcss8([ plugin ]);
+					result = await postcss.process(sourceCSS, processOptions);
+				} else {
+					result = await plugin.process(sourceCSS, processOptions, pluginOptions);
+				}
 				const resultCSS = result.css;
 
 				if (options.fix) {

test/postcss8-plugin.js

@@ -0,0 +1,14 @@
+module.exports = function testPlugin(options) {
+  return {
+    postcssPlugin: 'test-plugin',
+    Root (root, { result }) {
+      if (Object(options).shouldFail) {
+        throw new Error('This should fail.');
+      } else if (Object(options).shouldWarn) {
+        result.warn('This should warn.');
+      }
+    }
+  };
+};
+
+module.exports.postcss = true;