fix: Raise an Execution Exception before trying to decode a Query Response (#150)

Author: maticzav

Sources/SwiftGraphQLClient/Client/Selection.swift

@@ -87,7 +87,14 @@ extension GraphQLClient {
         policy: Operation.Policy = .cacheFirst
     ) -> AnyPublisher<DecodedOperationResult<T>, Error> where TypeLock: GraphQLHttpOperation {
         self.executeQuery(for: selection, as: operationName, url: request, policy: policy)
-            .tryMap { result in try result.decode(selection: selection) }
+            .tryMap { result in
+                // NOTE: If there was an error during the execution, we want to raise it before running
+                //       the decoder on the `data` which will most likely fail.
+                if let error = result.error {
+                    throw error
+                }
+                return try result.decode(selection: selection)
+            }
             .eraseToAnyPublisher()
     }
 
@@ -99,7 +106,14 @@ extension GraphQLClient {
         policy: Operation.Policy = .cacheFirst
     ) -> AnyPublisher<DecodedOperationResult<T>, Error> where TypeLock: GraphQLHttpOperation {
         self.executeMutation(for: selection, as: operationName, url: request, policy: policy)
-            .tryMap { result in try result.decode(selection: selection) }
+            .tryMap { result in
+                // NOTE: If there was an error during the execution, we want to raise it before running
+                //       the decoder on the `data` which will most likely fail.
+                if let error = result.error {
+                    throw error
+                }
+                return try result.decode(selection: selection)
+            }
             .eraseToAnyPublisher()
     }
 
@@ -111,7 +125,14 @@ extension GraphQLClient {
         policy: Operation.Policy = .cacheFirst
     ) -> AnyPublisher<DecodedOperationResult<T>, Error> where TypeLock: GraphQLWebSocketOperation {
         self.executeSubscription(of: selection, as: operationName, url: request, policy: policy)
-            .tryMap { result in try result.decode(selection: selection) }
+            .tryMap { result in
+                // NOTE: If there was an error during the execution, we want to raise it before running
+                //       the decoder on the `data` which will most likely fail.
+                if let error = result.error {
+                    throw error
+                }
+                return try result.decode(selection: selection)
+            }
             .eraseToAnyPublisher()
     }
 }