[2.x] Introduce ProvidesInertiaProps interface

src/ProvidesInertiaProps.php

@@ -0,0 +1,8 @@
+<?php
+
+namespace Inertia;
+
+interface ProvidesInertiaProps
+{
+    public function toInertiaProps(RenderContext $context): iterable;
+}

src/RenderContext.php

@@ -0,0 +1,15 @@
+<?php
+
+namespace Inertia;
+
+use Illuminate\Http\Request;
+
+class RenderContext
+{
+    public function __construct(
+        public string $component,
+        public Request $request
+    ) {
+        //
+    }
+}

src/Response.php

@@ -50,13 +50,15 @@ public function __construct(string $component, array $props, string $rootView =
     }
 
     /**
-     * @param  string|array  $key
+     * @param  string|array|ProvidesInertiaProps  $key
      * @param  mixed  $value
      * @return $this
      */
     public function with($key, $value = null): self
     {
-        if (is_array($key)) {
+        if ($key instanceof ProvidesInertiaProps) {
+            $this->props[] = $key;
+        } elseif (is_array($key)) {
             $this->props = array_merge($this->props, $key);
         } else {
             $this->props[$key] = $value;
@@ -131,6 +133,7 @@ public function toResponse($request)
      */
     public function resolveProperties(Request $request, array $props): array
     {
+        $props = $this->resolveInertiaPropsProviders($props, $request);
         $props = $this->resolvePartialProperties($props, $request);
         $props = $this->resolveArrayableProperties($props, $request);
         $props = $this->resolveAlways($props);
@@ -139,13 +142,37 @@ public function resolveProperties(Request $request, array $props): array
         return $props;
     }
 
+    /**
+     * Resolve the ProvidesInertiaProps props.
+     */
+    public function resolveInertiaPropsProviders(array $props, Request $request): array
+    {
+        $newProps = [];
+
+        $renderContext = new RenderContext($this->component, $request);
+
+        foreach ($props as $key => $value) {
+            if (is_numeric($key) && $value instanceof ProvidesInertiaProps) {
+                // Pipe into a Collection to leverage Collection::getArrayableItems()
+                $newProps = array_merge(
+                    $newProps,
+                    collect($value->toInertiaProps($renderContext))->all()
+                );
+            } else {
+                $newProps[$key] = $value;
+            }
+        }
+
+        return $newProps;
+    }
+
     /**
      * Resolve the `only` and `except` partial request props.
      */
     public function resolvePartialProperties(array $props, Request $request): array
     {
         if (! $this->isPartial($request)) {
-            return array_filter($this->props, static function ($prop) {
+            return array_filter($props, static function ($prop) {
                 return ! ($prop instanceof IgnoreFirstLoad);
             });
         }

src/ResponseFactory.php

@@ -151,12 +151,15 @@ public function always($value): AlwaysProp
     }
 
     /**
-     * @param  array|Arrayable  $props
+     * @param  array|Arrayable|ProvidesInertiaProps  $props
      */
     public function render(string $component, $props = []): Response
     {
         if ($props instanceof Arrayable) {
             $props = $props->toArray();
+        } elseif ($props instanceof ProvidesInertiaProps) {
+            // Will be resolved in Response::resolveResponsableProperties()
+            $props = [$props];
         }
 
         return new Response(

tests/ResponseFactoryTest.php

@@ -17,6 +17,8 @@
 use Inertia\LazyProp;
 use Inertia\MergeProp;
 use Inertia\OptionalProp;
+use Inertia\ProvidesInertiaProps;
+use Inertia\RenderContext;
 use Inertia\ResponseFactory;
 use Inertia\Tests\Stubs\ExampleMiddleware;
 
@@ -352,4 +354,28 @@ public function toArray()
             ],
         ]);
     }
+
+    public function test_will_accept_instances_of_provides_inertia_props()
+    {
+        Route::middleware([StartSession::class, ExampleMiddleware::class])->get('/', function () {
+            return Inertia::render('User/Edit', new class implements ProvidesInertiaProps
+            {
+                public function toInertiaProps(RenderContext $context): iterable
+                {
+                    return [
+                        'foo' => 'bar',
+                    ];
+                }
+            });
+        });
+
+        $response = $this->withoutExceptionHandling()->get('/', ['X-Inertia' => 'true']);
+        $response->assertSuccessful();
+        $response->assertJson([
+            'component' => 'User/Edit',
+            'props' => [
+                'foo' => 'bar',
+            ],
+        ]);
+    }
 }

tests/ResponseTest.php

@@ -17,6 +17,8 @@
 use Inertia\Inertia;
 use Inertia\LazyProp;
 use Inertia\MergeProp;
+use Inertia\ProvidesInertiaProps;
+use Inertia\RenderContext;
 use Inertia\Response;
 use Inertia\Tests\Stubs\FakeResource;
 use Inertia\Tests\Stubs\MergeWithSharedProp;
@@ -759,6 +761,33 @@ public function test_always_props_are_included_on_partial_reload(): void
         $this->assertFalse(isset($page->props->user));
     }
 
+    public function test_inertia_responsable_objects(): void
+    {
+        $request = Request::create('/user/123', 'GET');
+
+        $response = new Response('User/Edit', [
+            'foo' => 'bar',
+            new class implements ProvidesInertiaProps
+            {
+                public function toInertiaProps(RenderContext $context): iterable
+                {
+                    return collect([
+                        'baz' => 'qux',
+                    ]);
+                }
+            },
+            'quux' => 'corge',
+
+        ], 'app', '123');
+        $response = $response->toResponse($request);
+        $view = $response->getOriginalContent();
+        $page = $view->getData()['page'];
+
+        $this->assertSame('bar', $page['props']['foo']);
+        $this->assertSame('qux', $page['props']['baz']);
+        $this->assertSame('corge', $page['props']['quux']);
+    }
+
     public function test_inertia_response_type_prop(): void
     {
         $request = Request::create('/user/123', 'GET');
@@ -836,6 +865,30 @@ public function test_nested_dot_props_do_not_get_unpacked(): void
         $this->assertFalse(array_key_exists('can', $auth));
     }
 
+    public function test_props_can_be_added_using_the_with_method(): void
+    {
+        $request = Request::create('/user/123', 'GET');
+        $response = new Response('User/Edit', [], 'app', '123');
+
+        $response->with(['foo' => 'bar', 'baz' => 'qux'])
+            ->with(['quux' => 'corge'])
+            ->with(new class implements ProvidesInertiaProps
+            {
+                public function toInertiaProps(RenderContext $context): iterable
+                {
+                    return collect(['grault' => 'garply']);
+                }
+            });
+
+        $response = $response->toResponse($request);
+        $view = $response->getOriginalContent();
+        $page = $view->getData()['page'];
+
+        $this->assertSame('bar', $page['props']['foo']);
+        $this->assertSame('qux', $page['props']['baz']);
+        $this->assertSame('corge', $page['props']['quux']);
+    }
+
     public function test_responsable_with_invalid_key(): void
     {
         $request = Request::create('/user/123', 'GET');