bugfix: skip error parsing for 2xx responses on rejected promises

Author: lazerg

.changes/nextrelease/fix-wrappedhttphandler-2xx-error-parse.json

@@ -0,0 +1,7 @@
+[
+    {
+        "type": "bugfix",
+        "category": "",
+        "description": "Fixed WrappedHttpHandler buffering the entire partial response body into memory when a 2xx response was attached to a rejected promise, which could exhaust memory on a transport failure during a large streamed download."
+    }
+]

src/WrappedHttpHandler.php

@@ -168,8 +168,14 @@ private function parseError(
 
         $serviceError = "AWS HTTP error:\n";
 
-        if (!isset($err['response'])) {
-            $parts = ['response' => null];
+        // A 2xx status on a rejected promise means the transport failed
+        // mid-body after a success response was received; there is no error
+        // document to parse, and parsing one would buffer the entire partial
+        // body into memory.
+        if (!isset($err['response'])
+            || $err['response']->getStatusCode() < 300
+        ) {
+            $parts = ['response' => $err['response'] ?? null];
             $serviceError .= $err['exception']->getMessage();
         } else {
             try {

tests/WrappedHttpHandlerTest.php

@@ -93,6 +93,29 @@ public function testCanRejectWithoutResponse()
         }
     }
 
+    public function testDoesNotParseErrorWhenRejectedWithSuccessResponse()
+    {
+        $e = new \Exception('cURL error 18: transfer closed with outstanding read data remaining');
+        $cmd = new Command('foo');
+        $req = new Request('GET', 'http://foo.com');
+        $res = new Response(200, [], 'partial body');
+        $handler = function () use ($e, $res) {
+            return new RejectedPromise(['exception' => $e, 'response' => $res]);
+        };
+        $parser = $errorParser = [$this, 'fail'];
+        $wrapped = new WrappedHttpHandler($handler, $parser, $errorParser);
+        try {
+            $wrapped($cmd, $req)->wait();
+            $this->fail();
+        } catch (AwsException $e) {
+            $this->assertSame($cmd, $e->getCommand());
+            $this->assertSame($req, $e->getRequest());
+            $this->assertSame($res, $e->getResponse());
+            $this->assertNull($e->getResult());
+            $this->assertStringContainsString('cURL error 18', $e->getMessage());
+        }
+    }
+
     #[DataProvider('responseAndParserProvider')]
     public function testCanRejectWithAndParseResponse(
         Response $res,