feat(view): add :isset attribte (#1675)

brendt · web-flow · commit 1af3b23e843d · 2025-11-05T08:19:21.000+01:00
diff --git a/docs/1-essentials/02-views.md b/docs/1-essentials/02-views.md
@@ -177,7 +177,7 @@ Apart from HTMLs boolean attributes, the same syntax can be used with any expres
 
 ### Control flow directives
 
-#### `:if`, `:elseif` and `:else`
+#### `:if`, `:elseif`, and `:else`
 
 The `:if` directive can conditionally render the element it is attached to, depending on the result of its expression. Similarly, the `:elseif` and `:else` directives can be used on direct siblings for additional control.
 
@@ -186,6 +186,21 @@ The `:if` directive can conditionally render the element it is attached to, depe
 <span :else>Import {{ $this->pendingUploads->count() }} file(s)</span>
 ```
 
+#### `:isset`
+
+The `:isset` directive can be used to conditionally render the element it is attached to, depending on the existence of a variable.
+
+```html
+<h1 :isset="$title">{{ $title }}</h1>
+```
+
+Since `:isset` is a shorthand for `:if="isset()"`, it can be combined with `:elseif` and `:else`:
+
+```html
+<h1 :isset="$title">{{ $title }}</h1>
+<h1 :else>Title</h1>
+```
+
 #### `:foreach` and `:{:hl-keyword:forelse:}`
 
 The `:foreach` directive may be used to render the associated element multiple times based on the result of its expression. Combined with `:{:hl-keyword:forelse:}`, an empty state can be displayed when the data is empty.
@@ -230,7 +245,7 @@ To create a view component, create a `.view.php` file that starts with `x-`. The
 ```html app/x-base.view.php
 <html lang="en">
 	<head>
-		<title :if="$title">{{ $title }} — AirAcme</title>
+		<title :if="$title ?? null">{{ $title }} — AirAcme</title>
 		<title :else>AirAcme</title>
 	</head>
 	<body>
@@ -265,7 +280,7 @@ Attributes and [expression attributes](#expression-attributes) may be passed int
 
 ```html x-base.view.php
 // ...
-<title :if="$title">{{ $title }}</title>
+<title :if="$title ?? null">{{ $title }}</title>
 ```
 
 Note that the casing of attributes will affect the associated variable name:
diff --git a/docs/4-internals/03-view-spec.md b/docs/4-internals/03-view-spec.md
@@ -27,7 +27,7 @@ Some frontend frameworks also provide a `{html}:{:hl-property:attribute:}` synta
 
 ### Control structures
 
-Control structures like conditionals and loops are modelled with expression attributes. These control structure attributes are available: `{html}:{:hl-property:if:}`, `{html}:{:hl-property:elseif:}`, `{html}:{:hl-property:else:}`, `{html}:{:hl-property:foreach:}`, `{html}:{:hl-property:forelse:}`. Code within these control structures is compiled to valid PHP expressions.
+Control structures like conditionals and loops are modelled with expression attributes. These control structure attributes are available: `{html}:{:hl-property:if:}`, `{html}:{:hl-property:elseif:}`, `{html}:{:hl-property:else:}`, {:hl-property:isset:}`, `{html}:{:hl-property:foreach:}`, `{html}:{:hl-property:forelse:}`. Code within these control structures is compiled to valid PHP expressions.
 
 The following conditional:
 
diff --git a/packages/view/src/Attributes/AttributeFactory.php b/packages/view/src/Attributes/AttributeFactory.php
@@ -12,6 +12,7 @@ public function make(string $attributeName): Attribute
     {
         return match (true) {
             $attributeName === ':if' => new IfAttribute(),
+            $attributeName === ':isset' => new IssetAttribute(),
             $attributeName === ':elseif' => new ElseIfAttribute(),
             $attributeName === ':else' => new ElseAttribute(),
             $attributeName === ':foreach' => new ForeachAttribute(),
diff --git a/packages/view/src/Attributes/IssetAttribute.php b/packages/view/src/Attributes/IssetAttribute.php
@@ -0,0 +1,17 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Tempest\View\Attributes;
+
+use Tempest\View\Attribute;
+use Tempest\View\Element;
+use Tempest\View\Elements\PhpIfElement;
+
+final readonly class IssetAttribute implements Attribute
+{
+    public function apply(Element $element): Element
+    {
+        return new PhpIfElement($element);
+    }
+}
diff --git a/packages/view/src/Elements/PhpIfElement.php b/packages/view/src/Elements/PhpIfElement.php
@@ -46,10 +46,16 @@ public function setElse(Element $element): self
 
     public function compile(): string
     {
+        if ($condition = $this->wrappingElement->consumeAttribute(':isset')) {
+            $condition = sprintf('isset(%s)', $condition);
+        } else {
+            $condition = $this->wrappingElement->consumeAttribute(':if');
+        }
+
         $compiled = sprintf(
             '<?php if(%s): ?>
                 %s',
-            $this->wrappingElement->consumeAttribute(':if'),
+            $condition,
             $this->wrappingElement->compile(),
         );
 
diff --git a/tests/Integration/View/TempestViewRendererTest.php b/tests/Integration/View/TempestViewRendererTest.php
@@ -78,6 +78,34 @@ public function test_if_attribute(): void
         );
     }
 
+    public function test_isset_attribute(): void
+    {
+        $this->assertSame(
+            '',
+            $this->render(view('<div :isset="$foo">Hello</div>')),
+        );
+
+        $this->assertSame(
+            '<div>else</div>',
+            $this->render(view('<div :isset="$foo">Hello</div><div :else>else</div>')),
+        );
+
+        $this->assertSame(
+            '<div>elseif</div>',
+            $this->render(view('<div :isset="$foo">Hello</div><div :elseif="true">elseif</div><div :else>else</div>')),
+        );
+
+        $this->assertSame(
+            '<div>else</div>',
+            $this->render(view('<div :isset="$foo">Hello</div><div :elseif="false">elseif</div><div :else>else</div>')),
+        );
+
+        $this->assertSame(
+            '<div>Hello</div>',
+            $this->render(view('<div :isset="$foo">Hello</div>', foo: true)),
+        );
+    }
+
     public function test_if_with_other_expression_attributes(): void
     {
         $html = $this->render('<div :if="$this->show" :data="$data">Hello</div>', show: true, data: 'test');

Original file line number	Diff line number	Diff line change
`@@ -12,6 +12,7 @@ public function make(string $attributeName): Attribute`
`12`	`12`	`{`
`13`	`13`	`return match (true) {`
`14`	`14`	`$attributeName === ':if' => new IfAttribute(),`
	`15`	`+ $attributeName === ':isset' => new IssetAttribute(),`
`15`	`16`	`$attributeName === ':elseif' => new ElseIfAttribute(),`
`16`	`17`	`$attributeName === ':else' => new ElseAttribute(),`
`17`	`18`	`$attributeName === ':foreach' => new ForeachAttribute(),`