Core(Serialization): added warning message type

* Added message type 1 (warning) as described in [1].
* Added test which mirrors test for error message.

[1] https://github.com/lightning/bolts/blob/master/01-messaging.md#the-error-and-warning-messages

Upstream PR: joemphilips#229

src/DotNetLightning.Core/Serialization/Msgs/Msgs.fs

@@ -62,6 +62,9 @@ module internal TypeFlag =
     [<Literal>]
     let Error = 17us
 
+    [<Literal>]
+    let Warning = 1us
+
     [<Literal>]
     let Ping = 18us
 
@@ -210,6 +213,7 @@ module ILightningSerializable =
         match t with
         | TypeFlag.Init -> deserialize<InitMsg>(ls) :> ILightningMsg
         | TypeFlag.Error -> deserialize<ErrorMsg>(ls) :> ILightningMsg
+        | TypeFlag.Warning -> deserialize<WarningMsg>(ls) :> ILightningMsg
         | TypeFlag.Ping -> deserialize<PingMsg>(ls) :> ILightningMsg
         | TypeFlag.Pong -> deserialize<PongMsg>(ls) :> ILightningMsg
         | TypeFlag.OpenChannel ->
@@ -272,6 +276,11 @@ module ILightningSerializable =
 
             (d :> ILightningSerializable<ErrorMsg>)
                 .Serialize(ls)
+        | :? WarningMsg as warningMsg ->
+            ls.Write(TypeFlag.Warning, false)
+
+            (warningMsg :> ILightningSerializable<WarningMsg>)
+                .Serialize ls
         | :? PingMsg as d ->
             ls.Write(TypeFlag.Ping, false)
 
@@ -1809,6 +1818,50 @@ and WhichChannel =
     | SpecificChannel of ChannelId
     | All
 
+
+[<RequireQualifiedAccess>]
+[<CLIMutable>]
+type WarningMsg =
+    {
+        mutable ChannelId: WhichChannel
+        mutable Data: array<byte>
+    }
+
+    interface ISetupMsg
+
+    interface ILightningSerializable<WarningMsg> with
+        member this.Deserialize readStream =
+            match readStream.ReadUInt256 true with
+            | id when id = uint256.Zero -> this.ChannelId <- All
+            | id -> this.ChannelId <- SpecificChannel(ChannelId id)
+
+            this.Data <- readStream.ReadWithLen()
+
+        member this.Serialize writeStream =
+            match this.ChannelId with
+            | SpecificChannel(ChannelId id) -> writeStream.Write(id.ToBytes())
+            | All -> writeStream.Write(Array.zeroCreate 32)
+
+            writeStream.WriteWithLen this.Data
+
+    member this.GetFailureMsgData() =
+        let minPrintableAsciiChar = 32uy
+
+        let isPrintableAsciiChar(asciiChar: byte) =
+            asciiChar >= minPrintableAsciiChar
+
+        let isPrintableAsciiString =
+            this.Data |> Array.forall isPrintableAsciiChar
+
+        if isPrintableAsciiString then
+            System.Text.ASCIIEncoding.ASCII.GetString this.Data
+        else
+            Seq.fold
+                (fun msg (asciiChar: byte) -> sprintf "%s %02x" msg asciiChar)
+                "<warning contains non-printable binary data>:"
+                this.Data
+
+
 #nowarn "0044" // "This construct is deprecated" warning
 // sadly we don't have a way to restore warnings yet.
 // ref: https://github.com/fsharp/fslang-suggestions/issues/278

tests/DotNetLightning.Core.Tests/Serialization.fs

@@ -1814,6 +1814,25 @@ module SerializationTest =
 
                     Expect.equal (errorMsg.ToBytes()) (expected) ""
 
+                testCase "warning"
+                <| fun _ ->
+                    let warningMsg =
+                        {
+                            WarningMsg.ChannelId =
+                                WhichChannel.SpecificChannel(
+                                    ChannelId(
+                                        uint256 [| for _ in 0..31 -> 2uy |]
+                                    )
+                                )
+                            WarningMsg.Data = ascii.GetBytes "rust-lightning"
+                        }
+
+                    let expected =
+                        hex.DecodeData
+                            "0202020202020202020202020202020202020202020202020202020202020202000e727573742d6c696768746e696e67"
+
+                    Expect.equal (warningMsg.ToBytes()) expected ""
+
                 testCase "ping"
                 <| fun _ ->
                     let pingMsg =