add exception handling

Author: Jamil Maqdis Anton

src/Append.fs

@@ -1,7 +1,10 @@
 namespace SqlStreamStore.FSharp
 
 
+open System
+open Insurello.AsyncExtra
 open SqlStreamStore
+open SqlStreamStore.FSharp
 open SqlStreamStore.Streams
 
 type MessageDetails =
@@ -30,7 +33,21 @@ module Append =
 
             let append: IStreamStore -> StreamDetails -> MessageDetails -> Async<AppendResult> =
                 fun store streamDetails messageDetails ->
-                    store.AppendToStream(streamDetails.streamName, Helpers.toVersion streamDetails.version, createMessage messageDetails)
+                    store.AppendToStream
+                        (streamDetails.streamName, Helpers.toVersion streamDetails.version, createMessage messageDetails)
                     |> Async.AwaitTask
 
             append store streamDetails messageDetails
+
+module AppendExtras =
+    let appendNewMessage: IStreamStore -> StreamDetails -> MessageDetails -> AsyncResult<AppendResult, AppendException> =
+        fun store streamDetails messageDetails ->
+            Append.appendNewMessage store streamDetails messageDetails
+            |> Async.Catch
+            |> Async.map (function
+                | Choice1Of2 response -> Ok response
+                | Choice2Of2 exn ->
+                    Error
+                    <| match exn with
+                       | :? AggregateException as exn -> exn.InnerException |> AppendException.WrongExpectedVersion   
+                       | _ as exn -> exn |> AppendException.Other)          

src/SqlStreamStore.FSharp.fsproj

@@ -11,17 +11,17 @@
     </PropertyGroup>
 
     <ItemGroup>
-        <Compile Include="Types.fs"/>
-        <Compile Include="Append.fs"/>
-        <Compile Include="Read.fs"/>
-        <Compile Include="Postgres.fs"/>
+        <Compile Include="Types.fs" />
+        <Compile Include="Append.fs" />
+        <Compile Include="Read.fs" />
+        <Compile Include="Postgres.fs" />
     </ItemGroup>
 
     <ItemGroup>
-        <PackageReference Update="FSharp.Core" Version="4.7.2"/>
-        <PackageReference Include="Insurello.AsyncExtra" Version="1.1.0"/>
-        <PackageReference Include="SqlStreamStore" Version="1.2.0-beta.8"/>
-        <PackageReference Include="SqlStreamStore.Postgres" Version="1.2.0-beta.8"/>
+        <PackageReference Update="FSharp.Core" Version="4.7.2" />
+        <PackageReference Include="Insurello.AsyncExtra" Version="1.1.0" />
+        <PackageReference Include="SqlStreamStore" Version="1.2.0-beta.8" />
+        <PackageReference Include="SqlStreamStore.Postgres" Version="1.2.0-beta.8" />
     </ItemGroup>
 
 </Project>

src/Types.fs

@@ -16,6 +16,11 @@ type StreamDetails =
 type StartPositionInclusive = int64
 type MessageCount = int
 
+[<RequireQualifiedAccessAttribute>]
+type AppendException =
+    | WrongExpectedVersion of System.Exception
+    | Other of System.Exception
+
 module Helpers =
     let toVersion: Version -> int =
         function