[Swift] Optional Scalars Preparation (#6028)

* Perpares swift to take optional scalars + adds optional string helper method + disables linters in generated code

* Small fix for generated code

* Update grpc support to alpha 17 for swift

tests/FlatBuffers.GRPC.Swift/Package.swift

@@ -12,7 +12,7 @@ let package = Package(
     dependencies: [
         // Main SwiftNIO package
         .package(path: "../../swift"),
-        .package(url: "https://github.com/grpc/grpc-swift.git", from: "1.0.0-alpha.9")
+        .package(url: "https://github.com/grpc/grpc-swift.git", from: "1.0.0-alpha.17")
     ],
     targets: [
         // Targets are the basic building blocks of a package. A target can define a module or a test suite.

tests/FlatBuffers.GRPC.Swift/Sources/Model/greeter.grpc.swift

@@ -53,13 +53,13 @@ public extension GreeterProvider {
 	func handleMethod(_ methodName: String, callHandlerContext: CallHandlerContext) -> GRPCCallHandler? {
 		switch methodName {
 		case "SayHello":
-		return UnaryCallHandler(callHandlerContext: callHandlerContext) { context in
+		return CallHandlerFactory.makeUnary(callHandlerContext: callHandlerContext) { context in
 			return { request in
 				self.SayHello(request, context: context)
 			}
 		}
 		case "SayManyHellos":
-		return ServerStreamingCallHandler(callHandlerContext: callHandlerContext) { context in
+		return CallHandlerFactory.makeServerStreaming(callHandlerContext: callHandlerContext) { context in
 			return { request in
 				self.SayManyHellos(request: request, context: context)
 			}

tests/FlatBuffers.GRPC.Swift/Sources/Model/greeter_generated.swift

@@ -1,4 +1,5 @@
 // automatically generated by the FlatBuffers compiler, do not modify
+// swiftlint:disable all
 
 import FlatBuffers
 

tests/FlatBuffers.Test.Swift/Package.swift

@@ -11,7 +11,7 @@ let package = Package(
     ],
     dependencies: [
         .package(path: "../../swift/"),
-        .package(url: "https://github.com/grpc/grpc-swift.git", from: "1.0.0-alpha.12")
+        .package(url: "https://github.com/grpc/grpc-swift.git", from: "1.0.0-alpha.17")
     ],
     targets: [
         .target(name: "SwiftFlatBuffers"),

tests/FlatBuffers.Test.Swift/Tests/FlatBuffers.Test.SwiftTests/FlatBuffersTests.swift

@@ -59,6 +59,27 @@ final class FlatBuffersTests: XCTestCase {
         XCTAssertEqual(c.nameVector, [78, 111, 114, 119, 97, 121])
         XCTAssertEqual(c.name, country)
     }
+    
+    func testWriteOptionalValues() {
+        var b = FlatBufferBuilder()
+        let offset = b.create(string: nil)
+        createOptionalTable(b: &b, v: nil, off: offset)
+        let unitArray = b.sizedByteArray
+        // TODO: - Test function should be adjusted when the generation of optional scalars code is complete
+        let bb = ByteBuffer(bytes: unitArray)
+        let table = Table(bb: bb, position: Int32(bb.read(def: UOffset.self, position: bb.reader)) + Int32(bb.reader))
+        XCTAssertEqual(unitArray, [8, 0, 0, 0, 0, 0, 2, 0, 2, 0, 0, 0])
+        XCTAssertEqual(table.offset(4) == 0, true)
+        XCTAssertEqual(table.offset(6) == 0, true)
+    }
+    
+    func createOptionalTable(b: inout FlatBufferBuilder, v: Int?, off: Offset<String>) {
+        let start = b.startTable(with: 2)
+        b.add(offset: off, at: 6)
+        b.add(element: v, at: 4)
+        let root = Offset<UOffset>(offset: b.endTable(at: start))
+        b.finish(offset: root)
+    }
 }
 
 class Country {

tests/FlatBuffers.Test.Swift/Tests/FlatBuffers.Test.SwiftTests/monster_test.grpc.swift

@@ -65,23 +65,23 @@ public extension MonsterStorageProvider {
 	func handleMethod(_ methodName: String, callHandlerContext: CallHandlerContext) -> GRPCCallHandler? {
 		switch methodName {
 		case "Store":
-		return UnaryCallHandler(callHandlerContext: callHandlerContext) { context in
+		return CallHandlerFactory.makeUnary(callHandlerContext: callHandlerContext) { context in
 			return { request in
 				self.Store(request, context: context)
 			}
 		}
 		case "Retrieve":
-		return ServerStreamingCallHandler(callHandlerContext: callHandlerContext) { context in
+		return CallHandlerFactory.makeServerStreaming(callHandlerContext: callHandlerContext) { context in
 			return { request in
 				self.Retrieve(request: request, context: context)
 			}
 		}
 		case "GetMaxHitPoint":
-		return ClientStreamingCallHandler(callHandlerContext: callHandlerContext) { context in
+		return CallHandlerFactory.makeClientStreaming(callHandlerContext: callHandlerContext) { context in
 			self.GetMaxHitPoint(context: context)
 		}
 		case "GetMinMaxHitPoints":
-		return BidirectionalStreamingCallHandler(callHandlerContext: callHandlerContext) { context in
+		return CallHandlerFactory.makeBidirectionalStreaming(callHandlerContext: callHandlerContext) { context in
 			self.GetMinMaxHitPoints(context: context)
 		}
 		default: return nil;

tests/FlatBuffers.Test.Swift/Tests/FlatBuffers.Test.SwiftTests/monster_test_generated.swift

@@ -1,4 +1,5 @@
 // automatically generated by the FlatBuffers compiler, do not modify
+// swiftlint:disable all
 
 import FlatBuffers
 

tests/FlatBuffers.Test.Swift/Tests/FlatBuffers.Test.SwiftTests/union_vector_generated.swift

@@ -1,4 +1,5 @@
 // automatically generated by the FlatBuffers compiler, do not modify
+// swiftlint:disable all
 
 import FlatBuffers