feat(twig): Add attribute rendering system

src/TwigComponent/CHANGELOG.md

@@ -5,6 +5,7 @@
 -   Make `ComponentAttributes` traversable/countable
 -   Fixed lexing some `{# twig comments #}` with HTML Twig syntax
 -   Fix various usages of deprecated Twig code
+-   Add attribute rendering system
 
 ## 2.13.0
 

src/TwigComponent/doc/index.rst

@@ -945,6 +945,79 @@ the exception of *class*. For ``class``, the defaults are prepended:
     {# renders as: #}
     <button class="bar foo" type="submit">Save</button>
 
+Render
+~~~~~~
+
+.. versionadded:: 2.15
+
+    The ability to *render* attributes was added in TwigComponents 2.15.
+
+You can take full control over the attributes that are rendered by using the
+``render()`` method.
+
+.. code-block:: html+twig
+
+    {# templates/components/MyComponent.html.twig #}
+    <div
+      style="{{ attributes.render('style') }} display:block;"
+      {{ attributes }} {# be sure to always render the remaining attributes! #}
+    >
+      My Component!
+    </div>
+
+    {# render component #}
+    {{ component('MyComponent', { style: 'color:red;' }) }}
+
+    {# renders as: #}
+    <div style="color:red; display:block;">
+      My Component!
+    </div>
+
+.. caution::
+
+    There are a few important things to know about using ``render()``:
+
+    1. You need to be sure to call your ``render()`` methods before calling ``{{ attributes }}`` or some
+       attributes could be rendered twice. For instance:
+
+            .. code-block:: html+twig
+
+                {# templates/components/MyComponent.html.twig #}
+                <div
+                    {{ attributes }} {# called before style is rendered #}
+                    style="{{ attributes.render('style') }} display:block;"
+                >
+                    My Component!
+                </div>
+
+                {# render component #}
+                {{ component('MyComponent', { style: 'color:red;' }) }}
+
+                {# renders as: #}
+                <div style="color:red;" style="color:red; display:block;"> {# style is rendered twice! #}
+                    My Component!
+                </div>
+
+    2. If you add an attribute without calling ``render()``, it will be rendered twice. For instance:
+
+         .. code-block:: html+twig
+
+              {# templates/components/MyComponent.html.twig #}
+              <div
+                 style="display:block;" {# not calling attributes.render('style') #}
+                 {{ attributes }}
+              >
+                 My Component!
+              </div>
+
+              {# render component #}
+              {{ component('MyComponent', { style: 'color:red;' }) }}
+
+              {# renders as: #}
+              <div style="display:block;" style="color:red;"> {# style is rendered twice! #}
+                 My Component!
+              </div>
+
 Only
 ~~~~
 

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 +60,26 @@ function (string $carry, string $key) {
         );
     }
 
+    public function __clone(): void
+    {
+        $this->rendered = [];
+    }
+
+    public function render(string $attribute): ?string
+    {
+        if (null === $value = $this->attributes[$attribute] ?? null) {
+            return null;
+        }
+
+        if (!\is_string($value)) {
+            throw new \LogicException(sprintf('Can only get string attributes (%s is a %s).', $attribute, get_debug_type($value)));
+        }
+
+        $this->rendered[$attribute] = true;
+
+        return $value;
+    }
+
     /**
      * @return array<string, string|bool>
      */
@@ -89,6 +115,10 @@ 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/Fixtures/templates/components/RenderAttributes.html.twig

@@ -0,0 +1,7 @@
+<div
+    foo="{{ attributes.render('foo') }}"
+    bar="{{ attributes.render('bar')|default('default') }}"
+    baz="default {{ attributes.render('baz') }}"
+    qux="{{ attributes.render('qux') }} default"
+    {{ attributes }}
+/>

src/TwigComponent/tests/Integration/ComponentExtensionTest.php

@@ -216,6 +216,51 @@ public function testComponentPropsWithTrailingComma(): void
         $this->assertStringContainsString('Hello FOO, 123, and 456', $output);
     }
 
+    /**
+     * @dataProvider renderingAttributesManuallyProvider
+     */
+    public function testRenderingAttributesManually(array $attributes, string $expected): void
+    {
+        $actual = trim($this->renderComponent('RenderAttributes', $attributes));
+
+        $this->assertSame($expected, trim($actual));
+    }
+
+    public static function renderingAttributesManuallyProvider(): iterable
+    {
+        yield [
+            ['class' => 'block'],
+            <<<HTML
+            <div
+                foo=""
+                bar="default"
+                baz="default "
+                qux=" default"
+                 class="block"
+            />
+            HTML,
+        ];
+
+        yield [
+            [
+                'class' => 'block',
+                'foo' => 'value',
+                'bar' => 'value',
+                'baz' => 'value',
+                'qux' => 'value',
+            ],
+            <<<HTML
+            <div
+                foo="value"
+                bar="value"
+                baz="default value"
+                qux="value default"
+                 class="block"
+            />
+            HTML,
+        ];
+    }
+
     private function renderComponent(string $name, array $data = []): string
     {
         return self::getContainer()->get(Environment::class)->render('render_component.html.twig', [

src/TwigComponent/tests/Unit/ComponentAttributesTest.php

@@ -199,4 +199,29 @@ public function testIsTraversableAndCountable(): void
         $this->assertSame($attributes->all(), iterator_to_array($attributes));
         $this->assertCount(1, $attributes);
     }
+
+    public function testRenderSingleAttribute(): void
+    {
+        $attributes = new ComponentAttributes(['attr1' => 'value1', 'attr2' => 'value2']);
+
+        $this->assertSame('value1', $attributes->render('attr1'));
+        $this->assertNull($attributes->render('attr3'));
+    }
+
+    public function testRenderingSingleAttributeExcludesFromString(): void
+    {
+        $attributes = new ComponentAttributes(['attr1' => 'value1', 'attr2' => 'value2']);
+
+        $this->assertSame('value1', $attributes->render('attr1'));
+        $this->assertSame(' attr2="value2"', (string) $attributes);
+    }
+
+    public function testCannotRenderNonStringAttribute(): void
+    {
+        $attributes = new ComponentAttributes(['attr1' => false]);
+
+        $this->expectException(\LogicException::class);
+
+        $attributes->render('attr1');
+    }
 }