feat(twig): Add attribute merging behaviour

src/TwigComponent/CHANGELOG.md

@@ -3,6 +3,7 @@
 ## Unreleased
 
 -   Make `ComponentAttributes` traversable/countable.
+-   Add attribute merging behaviour system.
 
 ## 2.13.0
 

src/TwigComponent/src/ComponentAttributeValue.php

@@ -0,0 +1,42 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\UX\TwigComponent;
+
+/**
+ * @author Kevin Bond <kevinbond@gmail.com>
+ */
+final class ComponentAttributeValue implements \Stringable
+{
+    public function __construct(private string $value, private string $separator = ' ')
+    {
+    }
+
+    public function __toString(): string
+    {
+        return $this->value;
+    }
+
+    public function default(string $value): string
+    {
+        return $this->value ?: $value;
+    }
+
+    public function prepend(string $default): string
+    {
+        return trim(sprintf('%s%s%s', $default, $this->separator, $this->value));
+    }
+
+    public function append(string $default): string
+    {
+        return trim(sprintf('%s%s%s', $this->value, $this->separator, $default));
+    }
+}

src/TwigComponent/src/ComponentAttributes.php

@@ -21,6 +21,9 @@
  */
 final class ComponentAttributes implements \IteratorAggregate, \Countable
 {
+    /** @var array<string,true> */
+    private array $rendered = [];
+
     /**
      * @param array<string, string|bool> $attributes
      */
@@ -31,7 +34,10 @@ public function __construct(private array $attributes)
     public function __toString(): string
     {
         return array_reduce(
-            array_keys($this->attributes),
+            array_filter(
+                array_keys($this->attributes),
+                fn (string $key) => !isset($this->rendered[$key])
+            ),
             function (string $carry, string $key) {
                 $value = $this->attributes[$key];
 
@@ -54,6 +60,29 @@ function (string $carry, string $key) {
         );
     }
 
+    public function __clone(): void
+    {
+        $this->rendered = [];
+    }
+
+    public function __get(string $attribute): ComponentAttributeValue
+    {
+        return $this->render($attribute);
+    }
+
+    public function render(string $attribute, string $separator = ' '): ComponentAttributeValue
+    {
+        $value = $this->attributes[$attribute] ?? '';
+
+        if (!\is_string($value)) {
+            throw new \LogicException(sprintf('Cannot render attribute "%s" because it is not a string.', $attribute));
+        }
+
+        $this->rendered[$attribute] = true;
+
+        return new ComponentAttributeValue($value, $separator);
+    }
+
     /**
      * @return array<string, string|bool>
      */
@@ -89,6 +118,10 @@ public function defaults(iterable $attributes): self
             $attributes[$key] = $value;
         }
 
+        foreach (array_keys($this->rendered) as $attribute) {
+            unset($attributes[$attribute]);
+        }
+
         return new self($attributes);
     }
 

src/TwigComponent/tests/Unit/ComponentAttributesTest.php

@@ -199,4 +199,78 @@ public function testIsTraversableAndCountable(): void
         $this->assertSame($attributes->all(), iterator_to_array($attributes));
         $this->assertCount(1, $attributes);
     }
+
+    public function testRenderIndividualAttribute(): void
+    {
+        $attributes = new ComponentAttributes(['attr1' => 'value1', 'attr2' => 'value2']);
+
+        $this->assertSame('value1', (string) $attributes->render('attr1'));
+        $this->assertSame(' attr2="value2"', (string) $attributes);
+    }
+
+    public function testRenderIndividualAttributeUsingMagicGet(): void
+    {
+        $attributes = new ComponentAttributes(['attr1' => 'value1', 'attr2' => 'value2']);
+
+        $this->assertSame('value1', (string) $attributes->attr1);
+        $this->assertSame(' attr2="value2"', (string) $attributes);
+    }
+
+    public function testCannotRenderNonStringAttribute(): void
+    {
+        $attributes = new ComponentAttributes(['attr1' => false]);
+
+        $this->expectException(\LogicException::class);
+
+        $attributes->render('attr1');
+    }
+
+    public function testRenderedAttributeCanHaveADefault(): void
+    {
+        $attributes = new ComponentAttributes(['attr1' => 'value1', 'attr2' => 'value2']);
+
+        $this->assertSame('value1', $attributes->render('attr1')->default('default'));
+        $this->assertSame('default', $attributes->render('attr3')->default('default'));
+        $this->assertSame(' attr2="value2"', (string) $attributes);
+    }
+
+    public function testRenderedAttributeCanBePrepended(): void
+    {
+        $attributes = new ComponentAttributes(['attr1' => 'value1', 'attr2' => 'value2']);
+
+        $this->assertSame('default value1', $attributes->render('attr1')->prepend('default'));
+        $this->assertSame('default', $attributes->render('attr3')->prepend('default'));
+        $this->assertSame(' attr2="value2"', (string) $attributes);
+    }
+
+    public function testRenderedAttributeCanBeAppended(): void
+    {
+        $attributes = new ComponentAttributes(['attr1' => 'value1', 'attr2' => 'value2']);
+
+        $this->assertSame('value1 default', $attributes->render('attr1')->append('default'));
+        $this->assertSame('default', $attributes->render('attr3')->append('default'));
+        $this->assertSame(' attr2="value2"', (string) $attributes);
+    }
+
+    public function testDefaultsIgnoredIfAlreadyRendered(): void
+    {
+        $attributes = new ComponentAttributes(['attr1' => 'value1', 'attr2' => 'value2']);
+        $this->assertSame('value1', (string) $attributes->render('attr1'));
+
+        $attributes = $attributes->defaults(['attr1' => 'default']);
+
+        $this->assertSame(' attr2="value2"', (string) $attributes);
+    }
+
+    public function testCloningResetsRenderedAttributes(): void
+    {
+        $attributes = new ComponentAttributes(['attr1' => 'value1', 'attr2' => 'value2']);
+
+        $this->assertSame('value1', (string) $attributes->render('attr1'));
+        $this->assertSame(' attr2="value2"', (string) $attributes);
+
+        $attributes = clone $attributes;
+
+        $this->assertSame(' attr1="value1" attr2="value2"', (string) $attributes);
+    }
 }