Implement $firstMixin / $firstComponent function

Author: kylekatarnls

README.md

@@ -130,3 +130,41 @@ Contact us
   Footer of Contact page
 </footer>
 ```
+
+### Fallback component
+
+This package also include a function to get the first defined mixin/component
+among given names:
+
+```pug
+component page
+  | Page component
+
++#{$firstComponent('customPage', 'page')}
+```
+
+Output:
+
+```html
+Page component
+```
+
+And if `customPage` component is defined, it will be used instead:
+```pug
+component page
+  | Page component
+
+component customPage
+  | CustomPage component
+
++#{$firstComponent('customPage', 'page')}
+```
+
+Output:
+
+```html
+CustomPage component
+```
+
+(`$firstComponent` becomes `firstComponent` if you use pug-php or js-phpize)
+`$firstMixin` is also available as an alias.

src/Phug/Component/ComponentExtension.php

@@ -6,6 +6,7 @@
 use Phug\AbstractPlugin;
 use Phug\Ast\NodeInterface;
 use Phug\Compiler\Event\NodeEvent;
+use Phug\Compiler\Event\OutputEvent;
 use Phug\CompilerEvent;
 use Phug\Parser\NodeInterface as ParserNodeInterface;
 use Phug\Parser\Node\CodeNode;
@@ -113,13 +114,37 @@ public function handleNodeEvent(NodeEvent $event): void
         }
     }
 
+    public function handleOutputEvent(OutputEvent $event): void
+    {
+        $event->setOutput(
+            implode("\n", [
+                '<?php',
+                '$firstMixin = function (string ...$names) use (&$__pug_mixins) {',
+                '  foreach ($names as $name) {',
+                '    if (isset($__pug_mixins[$name])) {',
+                '      return $name;',
+                '    }',
+                '  }',
+                '  throw new \\InvalidArgumentException("No defined mixin/component in [".implode(", ", $names)."]");',
+                '};',
+                '$firstComponent = $firstMixin;',
+                '?>',
+            ]).
+            $event->getOutput()
+        );
+    }
+
     public function attachEvents(): void
     {
-        $this->getContainer()->getCompiler()->attach(CompilerEvent::NODE, [$this, 'handleNodeEvent']);
+        $compiler = $this->getCompiler();
+        $compiler->attach(CompilerEvent::NODE, [$this, 'handleNodeEvent']);
+        $compiler->attach(CompilerEvent::OUTPUT, [$this, 'handleOutputEvent']);
     }
 
     public function detachEvents(): void
     {
-        $this->getContainer()->getCompiler()->detach(CompilerEvent::NODE, [$this, 'handleNodeEvent']);
+        $compiler = $this->getCompiler();
+        $compiler->detach(CompilerEvent::NODE, [$this, 'handleNodeEvent']);
+        $compiler->detach(CompilerEvent::OUTPUT, [$this, 'handleOutputEvent']);
     }
 }

tests/Phug/Component/ComponentExtensionTest.php

@@ -325,6 +325,27 @@ public function testBasicMixinAreStillFine()
         ])));
     }
 
+    /**
+     * @covers ::handleOutputEvent
+     */
+    public function testFirstMixin()
+    {
+        $this->assertSame("<p>5</p>\nHello", $this->renderAndFormat(implode("\n", [
+            'mixin foo($num)',
+            '  p=$num',
+            '  block',
+            '+#{$firstMixin("biz", "foo", "bar")}(5)',
+            '  | Hello',
+        ])));
+        $this->assertSame("<p>5</p>\nHello", $this->renderAndFormat(implode("\n", [
+            'component foo($num)',
+            '  p=$num',
+            '  block',
+            '+#{$firstComponent("biz", "foo", "bar")}(5)',
+            '  | Hello',
+        ])));
+    }
+
     /**
      * @covers ::__construct
      * @covers ::getOptions