Return 404 for POST/PATCH requests with version > 0 for missing object

This reverts dba4944, which changed the response code from 404 to
412, on the grounds that the HTTP spec says 412 is appropriate for an
If-Match (or If-Unmodified-Since-Version, in our case) when the entity
doesn't exist. That makes sense for a PUT, which without the If-Match
would succeed, but, per the PATCH spec (RFC 5789), a PATCH for a missing
object should return a 404, and the HTTP spec (RFC 7232) also says that
"A server MUST ignore all received preconditions if its response to the
same request without those conditions would have been a status code
other than a 2xx (Successful) or 412 (Precondition Failed)."

controllers/ApiController.php

@@ -744,10 +744,15 @@ protected function checkSingleObjectWriteVersion($objectType, $obj=null, $json=f
 
 		$version = $headerVersion !== false ? $headerVersion : $propVersion;
 
-		// If object doesn't exist, version has to be 0
+		// If object doesn't exist, version has to be 0 if provided
 		if (!$obj) {
-			if ($version !== 0) {
-				$this->e404(ucwords($objectType) . " doesn't exist (to create, use version 0)");
+			// PATCH is only allowed for missing objects with version 0
+			if ($this->method == "PATCH" && $version === false) {
+				$this->e404(ucwords($objectType) . " not found "
+					. "(to create, use If-Unmodified-Since-Version: 0, JSON 'version' 0, or PUT method)");
+			}
+			if ($version > 0) {
+				$this->e404(ucwords($objectType) . " not found (expected version $version)");
 			}
 			return true;
 		}

model/API.inc.php

@@ -1246,12 +1246,8 @@ public static function checkJSONObjectVersion($object, $json, $requestParams, $r
 			}
 			// If a version is specified, the object has to exist
 			else if ($json->$versionProp > 0 && !$object->version) {
-				$code = 412;
-				if ($requestParams['v'] == 2) {
-					$code = 404;
-				}
 				throw new HTTPException(ucwords($objectType)
-					. " doesn't exist (expected version {$json->$versionProp}; use 0 instead)", $code);
+					. " doesn't exist (expected version {$json->$versionProp}; use 0 instead)", 404);
 			}
 		}
 		else {

tests/remote/tests/API/3/VersionTest.php

@@ -490,7 +490,7 @@ private function _testPatchExistingObjectWithoutVersion($objectType) {
 	}
 
 
-	// PATCH to a missing object with version header > 0 is a 412
+	// PATCH with version header > 0 to a missing object is a 404
 	public function testPatchMissingObjectWithVersionHeader() {
 		$this->_testPatchMissingObjectWithVersionHeader('collection');
 		$this->_testPatchMissingObjectWithVersionHeader('item');
@@ -511,11 +511,11 @@ private function _testPatchMissingObjectWithVersionHeader($objectType) {
 				"If-Unmodified-Since-Version: 123"
 			]
 		);
-		$this->assert412($response);
+		$this->assert404($response);
 	}
 
 
-	// PATCH to a missing object with version property > 0 is a 412
+	// PATCH with version property > 0 to a missing object is a 404
 	public function testPatchMissingObjectWithVersionProperty() {
 		$this->_testPatchMissingObjectWithVersionProperty('collection');
 		$this->_testPatchMissingObjectWithVersionProperty('item');
@@ -536,7 +536,7 @@ private function _testPatchMissingObjectWithVersionProperty($objectType) {
 				"Content-Type: application/json"
 			]
 		);
-		$this->assert412($response);
+		$this->assert404($response);
 	}
 
 
@@ -746,7 +746,7 @@ private function _testPatchMissingObjectsWithVersion0Property($objectType) {
 	}
 
 
-	// POST to a missing object with version > 0 is a 412 for that object
+	// POST with version > 0 to a missing object is a 404 for that object
 	public function testPatchMissingObjectsWithVersion() {
 		$this->_testPatchMissingObjectsWithVersion('collection');
 		$this->_testPatchMissingObjectsWithVersion('item');
@@ -766,7 +766,7 @@ private function _testPatchMissingObjectsWithVersion($objectType) {
 			json_encode([$json]),
 			array("Content-Type: application/json")
 		);
-		$this->assert412ForObject($response, ucwords($objectType)
+		$this->assert404ForObject($response, ucwords($objectType)
 			. " doesn't exist (expected version 123; use 0 instead)");
 	}