feat: Add idempotency (#1790)

Author: dplewis

Parse/Parse/Internal/Commands/CommandRunner/PFCommandRunningConstants.h

@@ -27,6 +27,7 @@ extern NSString *const PFCommandHeaderNameAppBuildVersion;
 extern NSString *const PFCommandHeaderNameAppDisplayVersion;
 extern NSString *const PFCommandHeaderNameOSVersion;
 extern NSString *const PFCommandHeaderNameSessionToken;
+extern NSString *const PFCommandHeaderNameRequestId;
 
 ///--------------------------------------
 #pragma mark - HTTP Method Override

Parse/Parse/Internal/Commands/CommandRunner/PFCommandRunningConstants.m

@@ -19,5 +19,6 @@
 NSString *const PFCommandHeaderNameAppDisplayVersion = @"X-Parse-App-Display-Version";
 NSString *const PFCommandHeaderNameOSVersion = @"X-Parse-OS-Version";
 NSString *const PFCommandHeaderNameSessionToken = @"X-Parse-Session-Token";
+NSString *const PFCommandHeaderNameRequestId = @"X-Parse-Request-Id";
 
 NSString *const PFCommandParameterNameMethodOverride = @"_method";

Parse/Parse/Internal/Commands/CommandRunner/URLRequestConstructor/PFCommandURLRequestConstructor.m

@@ -141,7 +141,7 @@ + (NSDictionary *)defaultURLRequestHeadersForApplicationId:(NSString *)applicati
     if (clientKey) {
         mutableHeaders[PFCommandHeaderNameClientKey] = clientKey;
     }
-
+    mutableHeaders[PFCommandHeaderNameRequestId] = [[NSUUID UUID] UUIDString];
     mutableHeaders[PFCommandHeaderNameClientVersion] = [versionPrefix stringByAppendingString:PARSE_VERSION];
     mutableHeaders[PFCommandHeaderNameOSVersion] = [PFDevice currentDevice].operatingSystemFullVersion;
 

Parse/Parse/Source/PFConstants.h

@@ -284,6 +284,10 @@ typedef NS_ENUM(NSInteger, PFErrorCode) {
      Application has exceeded its request limit.
      */
     kPFErrorRequestLimitExceeded = 155,
+    /**
+     Request was a duplicate and has been discarded due to idempotency rules.
+     */
+    kPFErrorDuplicateRequest = 159,
     /**
      Invalid event name.
      */

Parse/Tests/Unit/CommandURLRequestConstructorTests.m

@@ -155,6 +155,7 @@ - (void)testDefaultURLRequestHeaders {
     XCTAssertNotNil(headers[PFCommandHeaderNameOSVersion]);
     XCTAssertNotNil(headers[PFCommandHeaderNameAppBuildVersion]);
     XCTAssertNotNil(headers[PFCommandHeaderNameAppDisplayVersion]);
+    XCTAssertNotNil(headers[PFCommandHeaderNameRequestId]);
 }
 
 - (void)testBailOnEncodingError {