[5.x] Attribute Modifier

src/Modifiers/CoreModifiers.php

@@ -157,6 +157,48 @@ public function at($value, $params)
         return Stringy::at($value, Arr::get($params, 0));
     }
 
+    /**
+     * Returns an attribute ($params[0]) with its value when the given $value variable is not empty.
+     *
+     * @param  string  $value
+     * @param  array  $params
+     * @return string
+     */
+    public function attribute($value, $params)
+    {
+        if (! $name = Arr::get($params, 0)) {
+            throw new \Exception('Attribute name is required.');
+        }
+
+        if ($value instanceof Collection) {
+            $value = $value->all();
+        }
+
+        if (\is_array($value)) {
+            if (empty($value)) {
+                return '';
+            }
+
+            $value = \json_encode($value);
+        }
+
+        if (\is_bool($value)) {
+            return $value ? ' '.$name : '';
+        }
+
+        if (\is_object($value)) {
+            $value = (string) $value;
+        }
+
+        $value = trim($value);
+
+        if ($value === '') {
+            return '';
+        }
+
+        return sprintf(' %s="%s"', $name, Html::entities($value));
+    }
+
     /**
      * Returns a focal point as a background-position CSS value.
      *

tests/Modifiers/AttributeTest.php

@@ -0,0 +1,74 @@
+<?php
+
+namespace Tests\Modifiers;
+
+use Statamic\Modifiers\Modify;
+use Tests\TestCase;
+
+class AttributeTest extends TestCase
+{
+    /**
+     * @test
+     *
+     * @dataProvider attributeProvider
+     */
+    public function it_converts_to_attribute($value, $expected)
+    {
+        $this->assertEquals($expected, $this->modify($value, 'foo'));
+    }
+
+    public static function attributeProvider()
+    {
+        return [
+            'string' => ['bar baz', ' foo="bar baz"'],
+            'entities' => ['{<!&>}', ' foo="{&lt;!&amp;&gt;}"'],
+            'integer' => [1, ' foo="1"'],
+            'integer > 1' => [2, ' foo="2"'],
+            'negative integer' => [-1, ' foo="-1"'],
+            'float' => [1.5, ' foo="1.5"'],
+            'empty string' => ['', ''],
+            'true' => [true, ' foo'],
+            'false' => [false, ''],
+            'array' => [['one' => ['two' => 'three']], ' foo="{&quot;one&quot;:{&quot;two&quot;:&quot;three&quot;}}"'],
+            'empty array' => [[], ''],
+            'collection' => [collect(['one' => 'two']), ' foo="{&quot;one&quot;:&quot;two&quot;}"'],
+            'empty collection' => [collect(), ''],
+            'object with __toString' => [new AttributeTestStringable, ' foo="Test"'],
+        ];
+    }
+
+    /** @test */
+    public function it_throws_exception_without_argument()
+    {
+        $this->expectException(\Exception::class);
+        $this->expectExceptionMessage('Attribute name is required.');
+
+        $this->modify('value', null);
+    }
+
+    /** @test */
+    public function it_throws_exception_when_value_is_an_object_without_toString_method()
+    {
+        $this->expectException(\Exception::class);
+        $this->expectExceptionMessage('Object of class Tests\Modifiers\AttributeTestNotStringable could not be converted to string.');
+
+        $this->modify(new AttributeTestNotStringable, 'foo');
+    }
+
+    private function modify($value, $attribute)
+    {
+        return Modify::value($value)->attribute($attribute)->fetch();
+    }
+}
+
+class AttributeTestStringable
+{
+    public function __toString()
+    {
+        return 'Test';
+    }
+}
+
+class AttributeTestNotStringable
+{
+}