Support Object literal plugin usage

src/Config.js

@@ -63,7 +63,14 @@ module.exports = class extends ChainedMap {
             const args = stringify(value.__pluginArgs).slice(1, -1);
             return `${prefix}new ${constructorName}(${args})`;
           }
-          return prefix + stringify({ args: value.__pluginArgs || [] });
+          return (
+            prefix +
+            stringify(
+              value.__pluginArgs && value.__pluginArgs.length
+                ? { args: value.__pluginArgs }
+                : {}
+            )
+          );
         }
 
         // improve rule/use output

src/Plugin.js

@@ -8,7 +8,12 @@ module.exports = Orderable(
       this.name = name;
       this.extend(['init']);
 
-      this.init((Plugin, args = []) => new Plugin(...args));
+      this.init((Plugin, args = []) => {
+        if (typeof Plugin === 'function') {
+          return new Plugin(...args);
+        }
+        return Plugin;
+      });
     }
 
     use(plugin, args = []) {

test/Plugin.js

@@ -83,3 +83,17 @@ test('toConfig with custom expression', t => {
 
   t.is(initialized.__pluginConstructorName, `(require('my-plugin'))`);
 });
+
+test('toConfig with object literal plugin', t => {
+  const plugin = new Plugin(null, 'gamma');
+
+  const TestPlugin = {
+    apply() {},
+  };
+
+  plugin.use(TestPlugin);
+
+  const initialized = plugin.toConfig();
+
+  t.is(initialized, TestPlugin);
+});