Add an HTTP cache middleware

src/Illuminate/Http/Middleware/Cache.php

@@ -0,0 +1,49 @@
+<?php
+
+namespace Illuminate\Http\Middleware;
+
+use Closure;
+
+class Cache
+{
+    /**
+     * Add cache related HTTP headers.
+     *
+     * @param  \Illuminate\Http\Request  $request
+     * @param  \Closure  $next
+     * @param  int|null  $maxAge
+     * @param  int|null  $sharedMaxAge
+     * @param  bool|null $public
+     * @param  bool|null $etag
+     * @return \Symfony\Component\HttpFoundation\Response
+     */
+    public function handle($request, Closure $next, int $maxAge = null, int $sharedMaxAge = null, bool $public = null, bool $etag = false)
+    {
+        /**
+         * @var   \Symfony\Component\HttpFoundation\Response
+         */
+        $response = $next($request);
+
+        if (! $request->isMethodCacheable() || ! $response->getContent()) {
+            return $response;
+        }
+
+        if (! $response->getContent()) {
+            return;
+        }
+        if ($etag) {
+            $response->setEtag(md5($response->getContent()));
+        }
+        if (null !== $maxAge) {
+            $response->setMaxAge($maxAge);
+        }
+        if (null !== $sharedMaxAge) {
+            $response->setSharedMaxAge($sharedMaxAge);
+        }
+        if (null !== $public) {
+            $public ? $response->setPublic() : $response->setPrivate();
+        }
+
+        return $response;
+    }
+}

tests/Http/Middleware/CacheTest.php

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+<?php
+
+namespace Illuminate\Tests\Http\Middleware;
+
+use Illuminate\Http\Request;
+use Illuminate\Http\Response;
+use PHPUnit\Framework\TestCase;
+use Illuminate\Http\Middleware\Cache;
+
+class CacheTest extends TestCase
+{
+    public function testDoNotSetHeaderWhenMethodNotCacheable()
+    {
+        $request = new Request();
+        $request->setMethod('PUT');
+
+        $response = (new Cache())->handle($request, function () {
+            return new Response('Hello Laravel');
+        }, 1, 2, true, true);
+
+        $this->assertNull($response->getMaxAge());
+        $this->assertNull($response->getEtag());
+    }
+
+    public function testDoNotSetHeaderWhenNoContent()
+    {
+        $response = (new Cache())->handle(new Request(), function () {
+            return new Response();
+        }, 1, 2, true, true);
+
+        $this->assertNull($response->getMaxAge());
+        $this->assertNull($response->getEtag());
+    }
+
+    public function testAddHeaders()
+    {
+        $response = (new Cache())->handle(new Request(), function () {
+            return new Response('some content');
+        }, 100, 200, true, true);
+
+        $this->assertSame('"9893532233caff98cd083a116b013c0b"', $response->getEtag());
+        $this->assertSame('max-age=100, public, s-maxage=200', $response->headers->get('Cache-Control'));
+    }
+}