Option.traverseAsync and traverseTask now allow mapping to new types

Author: PaigeM89

src/FsToolkit.ErrorHandling/Option.fs

@@ -347,9 +347,9 @@ module Option =
     /// <param name="opt">The <c>option</c> to map over.</param>
     /// <returns>A <c>Task&lt;'T option&gt;</c> with the mapped value.</returns>
     let inline traverseTask
-        ([<InlineIfLambda>] f: 'T -> Task<'T>)
+        ([<InlineIfLambda>] f: 'T -> Task<'U>)
         (opt: Option<'T>)
-        : Task<Option<'T>> =
+        : Task<Option<'U>> =
         sequenceTask ((map f) opt)
 
     /// <summary>
@@ -409,9 +409,9 @@ module Option =
     /// <param name="opt">The Option to map over.</param>
     /// <returns>An Async Option with the mapped value.</returns>
     let inline traverseAsync
-        ([<InlineIfLambda>] f: 'T -> Async<'T>)
+        ([<InlineIfLambda>] f: 'T -> Async<'U>)
         (opt: Option<'T>)
-        : Async<Option<'T>> =
+        : Async<Option<'U>> =
         sequenceAsync ((map f) opt)
 
     /// <summary>

tests/FsToolkit.ErrorHandling.Tests/Option.fs

@@ -275,6 +275,19 @@ let traverseTaskTests =
                 Expect.equal value (Some "foo") ""
             }
 
+        testCaseTask "traverseTask allows mapping to new type"
+        <| fun () ->
+            task {
+                let optTask = Some 100
+                let optFunc =
+                    string
+                    >> Task.singleton
+                let! value = 
+                    (optFunc, optTask)
+                    ||> Option.traverseTask
+                Expect.equal value (Some "100") ""
+            }
+
         testCaseTask "traverseTask returns None if None"
         <| fun () ->
             task {
@@ -439,6 +452,18 @@ let traverseAsyncTests =
             Expect.equal value (Some "foo") ""
         }
 
+        testCaseAsync "traverseAsync allows mapping to different types"
+        <| async {
+            let optAsync = Some 100
+            let optFunc =
+                (fun i -> string i)
+                >> Async.singleton
+            let! value =
+                (optFunc, optAsync)
+                ||> Option.traverseAsync
+            Expect.equal value (Some "100") ""
+        }
+
         testCaseAsync "traverseAsync returns None if None"
         <| async {
             let optAsync = None