feature: Adds support for GraphQL over HTTP media type (apollographql/apollo-ios-dev#558)

Author: calvincestari

Sources/Apollo/MultipartResponseDeferParser.swift

@@ -13,7 +13,7 @@ struct MultipartResponseDeferParser: MultipartResponseSpecificationParser {
       switch self {
 
       case let .unsupportedContentType(type):
-        return "Unsupported content type: application/json is required but got \(type)."
+        return "Unsupported content type: 'application/graphql-response+json' or 'application/json' are supported, received '\(type)'."
       case .cannotParseChunkData:
         return "The chunk data could not be parsed."
       case .cannotParsePayloadData:
@@ -53,7 +53,7 @@ struct MultipartResponseDeferParser: MultipartResponseSpecificationParser {
     for dataLine in chunk.components(separatedBy: Self.dataLineSeparator.description) {
       switch DataLine(dataLine.trimmingCharacters(in: .newlines)) {
       case let .contentHeader(directives):
-        guard directives.contains("application/json") else {
+        guard directives.contains(where: { $0.isValidGraphQLContentType }) else {
           return .failure(ParsingError.unsupportedContentType(type: directives.joined(separator: ";")))
         }
 

Sources/Apollo/MultipartResponseParsingInterceptor.swift

@@ -194,4 +194,8 @@ extension String {
       .components(separatedBy: ";")
       .map({ $0.trimmingCharacters(in: .whitespaces) })
   }
+
+  var isValidGraphQLContentType: Bool {
+    self == "application/json" || self == "application/graphql-response+json"
+  }
 }

Sources/Apollo/MultipartResponseSubscriptionParser.swift

@@ -15,7 +15,7 @@ struct MultipartResponseSubscriptionParser: MultipartResponseSpecificationParser
       switch self {
 
       case let .unsupportedContentType(type):
-        return "Unsupported content type: application/json is required but got \(type)."
+        return "Unsupported content type: 'application/graphql-response+json' or 'application/json' are supported, received '\(type)'."
       case .cannotParseChunkData:
         return "The chunk data could not be parsed."
       case let .irrecoverableError(message):
@@ -71,7 +71,7 @@ struct MultipartResponseSubscriptionParser: MultipartResponseSpecificationParser
         break
 
       case let .contentHeader(directives):
-        guard directives.contains("application/json") else {
+        guard directives.contains(where: { $0.isValidGraphQLContentType }) else {
           return .failure(ParsingError.unsupportedContentType(type: directives.joined(separator: ";")))
         }
 

Sources/Apollo/RequestChainNetworkTransport.swift

@@ -103,13 +103,13 @@ open class RequestChainNetworkTransport: NetworkTransport {
     if Operation.operationType == .subscription {
       request.addHeader(
         name: "Accept",
-        value: "multipart/mixed;\(MultipartResponseSubscriptionParser.protocolSpec),application/json"
+        value: "multipart/mixed;\(MultipartResponseSubscriptionParser.protocolSpec),application/graphql-response+json,application/json"
       )
 
     } else {
       request.addHeader(
         name: "Accept",
-        value: "multipart/mixed;\(MultipartResponseDeferParser.protocolSpec),application/json"
+        value: "multipart/mixed;\(MultipartResponseDeferParser.protocolSpec),application/graphql-response+json,application/json"
       )
     }