Issue 2426 improve response code error api

Sources/Apollo/ResponseCodeInterceptor.swift

@@ -33,6 +33,17 @@ public struct ResponseCodeInterceptor: ApolloInterceptor {
         return errorStrings.joined(separator: " ")
       }
     }
+
+    public var graphQLError: GraphQLError? {
+      switch self {
+      case .invalidResponseCode(_, let rawData):
+        if let jsonRawData = rawData,
+           let jsonData = try? JSONSerialization.jsonObject(with: jsonRawData, options: .allowFragments) as? JSONObject {
+          return GraphQLError(jsonData)
+        }
+        return nil
+      }
+    }
   }
 
   /// Designated initializer

Tests/ApolloTests/Interceptors/ResponseCodeInterceptorTests.swift

@@ -106,17 +106,96 @@ class ResponseCodeInterceptorTests: XCTestCase {
           guard
             let data = rawData,
             let dataString = String(bytes: data, encoding: .utf8) else {
-              XCTFail("Incorrect data returned with error")
-              return
+            XCTFail("Incorrect data returned with error")
+            return
           }
-
+
+          guard
+            let castError = error as? ResponseCodeInterceptor.ResponseCodeError,
+            let dataEntry = castError.graphQLError?["data"] as? JSONObject,
+            let heroEntry = dataEntry["hero"] as? JSONObject,
+            let typeName = heroEntry["__typename"] as? String,
+            let heroName = heroEntry["name"] as? String
+          else {
+            XCTFail("Invalid GraphQL Error")
+            return
+          }
+          XCTAssertEqual("GraphQL Error", castError.graphQLError?.description)
+          XCTAssertEqual("Human", typeName)
+          XCTAssertEqual("Luke Skywalker", heroName)
+
           XCTAssertEqual(dataString, "{\"data\":{\"hero\":{\"__typename\":\"Human\",\"name\":\"Luke Skywalker\"}}}")
         default:
           XCTFail("Unexpected error type: \(error.localizedDescription)")
         }
       }
     }
-
+
+    self.wait(for: [expectation], timeout: 1)
+  }
+
+  func testResponseCodeInterceptorDoesNotHaveGraphQLError() {
+    class TestProvider: InterceptorProvider {
+      let mockClient: MockURLSessionClient = {
+        let client = MockURLSessionClient()
+        client.response = HTTPURLResponse(url: TestURL.mockServer.url,
+                                          statusCode: 401,
+                                          httpVersion: nil,
+                                          headerFields: nil)
+        client.data = "Not a GraphQL Error".data(using: .utf8)
+        return client
+      }()
+
+      func interceptors<Operation: GraphQLOperation>(
+        for operation: Operation
+      ) -> [any ApolloInterceptor] {
+        [
+          NetworkFetchInterceptor(client: self.mockClient),
+          ResponseCodeInterceptor(),
+          JSONResponseParsingInterceptor(),
+        ]
+      }
+    }
+
+    let network = RequestChainNetworkTransport(interceptorProvider: TestProvider(),
+                                               endpointURL: TestURL.mockServer.url)
+
+    let expectation = self.expectation(description: "Request sent")
+
+    _ = network.send(operation: MockQuery.mock()) { result in
+      defer {
+        expectation.fulfill()
+      }
+
+      switch result {
+      case .success:
+        XCTFail("This should not have succeeded")
+      case .failure(let error):
+        switch error {
+        case ResponseCodeInterceptor.ResponseCodeError.invalidResponseCode(response: let response, let rawData):
+          XCTAssertEqual(response?.statusCode, 401)
+
+          guard
+            let data = rawData,
+            let dataString = String(bytes: data, encoding: .utf8) else {
+            XCTFail("Incorrect data returned with error")
+            return
+          }
+
+          guard let castError = error as? ResponseCodeInterceptor.ResponseCodeError else {
+            XCTFail("It should be a ResponseCodeError")
+            return
+          }
+
+          XCTAssertNil(castError.graphQLError)
+
+          XCTAssertEqual(dataString, "Not a GraphQL Error")
+        default:
+          XCTFail("Unexpected error type: \(error.localizedDescription)")
+        }
+      }
+    }
+
     self.wait(for: [expectation], timeout: 1)
   }
 }