Add Prelude.reraise'

helper funstion to easy reraise exceptions even outside of try-with

Author: sideeffffect

src/FSharpx.Extras/ComputationExpressions/Monad.fs

@@ -244,6 +244,12 @@ module Option =
         | Some x -> x
         | None -> raise e
 
+    /// Gets the value associated with the option or reraises the supplied exception.
+    let inline getOrReraise e =
+        function
+        | Some x -> x
+        | None -> reraise' e
+
     /// Gets the value associated with the option or the default value for the type.
     let getOrDefault =
         function
@@ -748,12 +754,19 @@ module Choice =
         | Choice2Of2 e -> invalidArg "choice" (sprintf "The choice value was Choice2Of2 '%A'" e)
     
     /// If Choice is 1Of2, return its value.
-    /// Otherwise throw the exception in 2Of2.
+    /// Otherwise raise the exception in 2Of2.
     let getOrRaise<'a, 'exn when 'exn :> exn> (c:Choice<'a, 'exn>) =
         match c with
         | Choice1Of2 r -> r
         | Choice2Of2 e -> raise e
 
+    /// If Choice is 1Of2, return its value.
+    /// Otherwise reraise the exception in 2Of2.
+    let getOrReraise<'a, 'exn when 'exn :> exn> (c:Choice<'a, 'exn>) =
+        match c with
+        | Choice1Of2 r -> r
+        | Choice2Of2 e -> reraise' e
+    
     /// Wraps a function, encapsulates any exception thrown within to a Choice
     let inline protect f x = 
         try
@@ -1073,7 +1086,7 @@ module Task =
 
             let wrapCrash (e:exn) : Task<'a> =
                 compensation()
-                raise e
+                reraise' e
 
             this.Bind(this.TryWith(body, wrapCrash), wrapOk)
 
@@ -1151,7 +1164,7 @@ module Task =
 
             let wrapCrash (e:exn) : TokenToTask<'a> =
                 compensation()
-                raise e
+                reraise' e
 
             this.Bind(this.TryWith(body, wrapCrash), wrapOk)
 
@@ -1243,4 +1256,4 @@ module Task =
     /// Creates a task that executes all the given tasks.
     /// The paralelism is throttled, so that at most `throttle` tasks run at one time.
     let ParallelWithThrottle throttle (tasks : seq<unit -> Task<'a>>) : (Task<'a[]>) =
-        ParallelWithThrottleCustom Choice.getOrRaise throttle tasks
+        ParallelWithThrottleCustom Choice.getOrReraise throttle tasks

src/FSharpx.Extras/Prelude.fs

@@ -3,6 +3,7 @@
 open System
 open System.Globalization
 open System.Diagnostics
+open System.Runtime.ExceptionServices
 
 [<AutoOpen>]
 module Prelude =
@@ -74,6 +75,14 @@ module Prelude =
     /// Custom operator for `tee`: Given a value, apply a function to it, ignore the result, then return the original value.
     let inline (|>!) x fn = tee fn x
 
+    /// Rethrows an exception. This can be used even outside of try-with block. The exception object (stacktrace, etc) is not changed.
+    let reraise' (e:exn) : 'T = ExceptionDispatchInfo.Capture(e).Throw() ; undefined
+    // http://thorarin.net/blog/post/2013/02/21/Preserving-Stack-Trace.aspx
+    // https://stackoverflow.com/questions/7168801/how-to-use-reraise-in-async-workflows-in-f
+
+    /// Rethrows an exception, but bebore that applies a function on it. This can be used even outside of try-with block. The exception object (stacktrace, etc) is not changed.
+    let reraiseWith (f : exn -> unit) (e:exn) : 'T = f e ; reraise' e
+
     let inline toOption x = match x with
                             | true, v -> Some v
                             | _       -> None