Add Exception module

Author: gusty

src/FSharpPlus/Control/Monoid.fs

@@ -31,11 +31,8 @@ type Plus =
     #if !FABLE_COMPILER
     static member        ``+`` (x: StringBuilder     , y: StringBuilder     , [<Optional>]_mthd: Plus    ) = StringBuilder().Append(x).Append(y)
     static member        ``+`` (_: Id0               , _: Id0               , [<Optional>]_mthd: Plus    ) = Id0 ""    
-    static member        ``+`` (x: AggregateException, y: AggregateException, [<Optional>]_mthd: Plus    ) = new AggregateException (seq {yield! x.InnerExceptions; yield! y.InnerExceptions})
-    static member        ``+`` (x: exn               , y: exn               , [<Optional>]_mthd: Plus    ) =
-        let f (e: exn) = match e with :? AggregateException as a -> a.InnerExceptions :> seq<_> | _ -> Seq.singleton e
-        let left = f x
-        new AggregateException (seq { yield! left; yield! Seq.except left (f y) }) :> exn
+    static member        ``+`` (x: AggregateException, y: AggregateException, [<Optional>]_mthd: Plus    ) = Exception.add x y
+    static member        ``+`` (x: exn               , y: exn               , [<Optional>]_mthd: Plus    ) = Exception.add x y :> exn
     #else
     static member        ``+`` (x: StringBuilder     , y: StringBuilder     , [<Optional>]_mthd: Plus    ) = StringBuilder().Append(string x).Append(string y)
     static member        ``+`` (_: Id0               , _: Id0               , [<Optional>]_mthd: Plus    ) = Id0 ""

src/FSharpPlus/Extensions/Exception.fs

@@ -0,0 +1,30 @@
+namespace FSharpPlus
+
+/// Additional operations on Exception
+[<RequireQualifiedAccess>]
+module Exception =
+    open System
+    open System.Runtime.ExceptionServices
+    open FSharpPlus.Internals.Errors
+    
+    #if !FABLE_COMPILER
+
+    /// Throws the given exception with its original stacktrace.
+    let inline rethrow<'T> (exn: exn) =
+        raiseIfNull (nameof exn) exn
+        (ExceptionDispatchInfo.Capture exn).Throw ()
+        Unchecked.defaultof<'T>    
+    
+    /// Combines exceptions from 2 exceptions into a single AggregateException.
+    /// Exceptions already present in the first argument won't be added.
+    let add (exn1: exn) (exn2: exn) =
+        raiseIfNull (nameof exn1) exn1
+        raiseIfNull (nameof exn2) exn2
+        let f (e: exn) =
+            match e with
+            :? AggregateException as a -> a.InnerExceptions :> seq<_>
+            | _ -> Seq.singleton e
+        let left = f exn1
+        new AggregateException (seq { yield! left; yield! Seq.except left (f exn2) })
+
+    #endif

src/FSharpPlus/FSharpPlus.fsproj

@@ -38,6 +38,7 @@
     <Compile Include="Extensions/Nullable.fs" />
     <Compile Include="Extensions/Result.fs" />
     <Compile Include="Extensions/Choice.fs" />
+    <Compile Include="Extensions/Exception.fs" />
     <Compile Include="Extensions/Seq.fs" />
     <Compile Include="Extensions/IList.fs" />
     <Compile Include="Extensions/List.fs" />