Merge branch 'andybeak-abeak/allow_no_cache_header'

Closes #21

Author: akrabat

src/Cache.php

@@ -56,12 +56,20 @@ public function __invoke(RequestInterface $request, ResponseInterface $response,
 
         // Cache-Control header
         if (!$response->hasHeader('Cache-Control')) {
-            $response = $response->withHeader('Cache-Control', sprintf(
-                '%s, max-age=%s%s',
-                $this->type,
-                $this->maxAge,
-                $this->mustRevalidate ? ', must-revalidate' : ''
-            ));
+            if ($this->maxAge === 0) {
+                $response = $response->withHeader('Cache-Control', sprintf(
+                    '%s, no-cache%s',
+                    $this->type,
+                    $this->mustRevalidate ? ', must-revalidate' : ''
+                ));
+            } else {
+                $response = $response->withHeader('Cache-Control', sprintf(
+                    '%s, max-age=%s%s',
+                    $this->type,
+                    $this->maxAge,
+                    $this->mustRevalidate ? ', must-revalidate' : ''
+                ));
+            }
         }
 
         // Last-Modified header and conditional GET check

tests/CacheTest.php

@@ -52,6 +52,21 @@ public function testCacheControlHeaderWithMustRevalidate()
         $this->assertEquals('private, max-age=86400, must-revalidate', $cacheControl);
     }
 
+    public function testCacheControlHeaderWithZeroMaxAge()
+    {
+        $cache = new Cache('private', 0, false);
+        $req = $this->requestFactory();
+        $res = new Response();
+        $next = function (Request $req, Response $res) {
+            return $res;
+        };
+        $res = $cache($req, $res, $next);
+
+        $cacheControl = $res->getHeaderLine('Cache-Control');
+
+        $this->assertEquals('private, no-cache', $cacheControl);
+    }
+
     public function testCacheControlHeaderDoesNotOverrideExistingHeader()
     {
         $cache = new Cache('public', 86400);