+ .net8 target framework and F# language version 8 (#573)

- Add: .net8 target framework for F#+ library
- Update: F# language version to 8
- Fix: A unique overload for method 'DateTime' could not be determined
- Fix: Indentation warnings that has turned into compilation error
- Fix: Fable 3.7 runs with downgraded .net versions and target framework

Author: wallymathieu

.config/dotnet-tools.json

@@ -3,7 +3,7 @@
   "isRoot": true,
   "tools": {
     "fable": {
-      "version": "4.1.4",
+      "version": "4.5.0",
       "commands": [
         "fable"
       ]

.github/workflows/fable.yml

@@ -17,6 +17,10 @@ jobs:
       run: git submodule update --init --recursive
     - name: Remove global json
       run: rm global.json
+    - name: Set target framework to net6 instead of net8
+      uses: Mudlet/xmlstarlet-action@master
+      with:
+        args: edit --inplace --update "/Project/PropertyGroup/TargetFrameworks" --value "netstandard2.0;netstandard2.1;net6.0" ./src/FSharpPlus/FSharpPlus.fsproj
     - name: Setup .NET Core
       uses: actions/setup-dotnet@v3
       with:
@@ -26,8 +30,11 @@ jobs:
           6.0.x
     - name: Restore tools
       run: dotnet tool restore
+    - name: Create global.json
+      working-directory: tests/FSharpPlusFable.Tests
+      run: mv fable3-global.json global.json
     - name: Install fable
-      run: dotnet tool install --global Fable --version 3.7.20
+      run: dotnet tool install --global Fable --version 3.7.22
     - name: Use Node.js
       uses: actions/setup-node@v1
       with:
@@ -83,9 +90,6 @@ jobs:
       run: git submodule update --init --recursive
     - name: Remove global json
       run: rm global.json
-    - name: Remove global json in subfolder
-      run: rm global.json
-      working-directory: tests/FSharpPlusFable.Tests
     - name: Setup .NET Core
       uses: actions/setup-dotnet@v3
       with:

src/FSharpPlus/FSharpPlus.fsproj

@@ -21,12 +21,14 @@
     <AutoGenerateBindingRedirects>true</AutoGenerateBindingRedirects>
     <Configurations>Debug;Release;Fable;Fable3;Test</Configurations>
     <Platforms>AnyCPU</Platforms>
-    <LangVersion>6.0</LangVersion>
+    <LangVersion>8.0</LangVersion>
+    <LangVersion Condition=" '$(Configuration)' == 'Fable' OR '$(Configuration)' == 'Fable3' ">6.0</LangVersion>
+
     <DefineConstants Condition=" '$(Configuration)' == 'Test'">$(DefineConstants);TEST_TRACE</DefineConstants>
     <DefineConstants Condition=" '$(Configuration)' == 'Fable'">$(DefineConstants);FABLE_COMPILER</DefineConstants>
     <DefineConstants Condition=" '$(Configuration)' == 'Fable3'">$(DefineConstants);FABLE_COMPILER;FABLE_COMPILER_3</DefineConstants>
     <DefineConstants Condition=" '$(Configuration)' == 'Fable4'">$(DefineConstants);FABLE_COMPILER;FABLE_COMPILER_4</DefineConstants>
-    <TargetFrameworks>netstandard2.0;netstandard2.1</TargetFrameworks>
+    <TargetFrameworks>netstandard2.0;netstandard2.1;net8.0</TargetFrameworks>
     <!--<OutputPath>..\..\bin</OutputPath>-->
   </PropertyGroup>
   <ItemGroup>

tests/FSharpPlus.Tests/FSharpPlus.Tests.fsproj

@@ -12,7 +12,7 @@
     <Platforms>AnyCPU</Platforms>
     <DefineConstants Condition=" '$(Configuration)' == 'Test'">$(DefineConstants);TEST_TRACE</DefineConstants>
     <DefineConstants Condition=" '$(Configuration)' == 'Fable'">$(DefineConstants);FABLE_COMPILER</DefineConstants>
-    <TargetFramework>net7.0</TargetFramework>
+    <TargetFrameworks>net7.0;net8.0</TargetFrameworks>
   </PropertyGroup>
   <ItemGroup>
     <Compile Include="Helpers.fs" />

tests/FSharpPlus.Tests/General.fs

@@ -1945,7 +1945,7 @@ module Memoization =
 
         let f x                       = printfn "calculating"; effs.Add "f"; string x
         let g x (y:string) z : uint32 = printfn "calculating"; effs.Add "g"; uint32 (x * int y + int z)
-        let h x y z                   = printfn "calculating"; effs.Add "h"; new System.DateTime (x, y, z)
+        let h (x: int) (y: int) (z: int) = printfn "calculating"; effs.Add "h"; new System.DateTime (x, y, z)
         let sum2 (a:int)       = printfn "calculating"; effs.Add "sum2"; (+) a
         let sum3 a (b:int) c   = printfn "calculating"; effs.Add "sum3"; a + b + c
         let sum4 a b c d : int = printfn "calculating"; effs.Add "sum4"; a + b + c + d

tests/FSharpPlusFable.Tests/FSharpTests/General.fs

@@ -311,7 +311,7 @@ let memoization = testList "Memoization" [
 
         let f x                       = printfn "calculating"; effs.Add "f"; string x
         let g x (y:string) z : uint32 = printfn "calculating"; effs.Add "g"; uint32 (x * int y + int z)
-        let h x y z                   = printfn "calculating"; effs.Add "h"; new System.DateTime (x, y, z)
+        let h (x: int) (y: int) (z: int) = printfn "calculating"; effs.Add "h"; new System.DateTime (x, y, z)
         let sum2 (a:int)       = printfn "calculating"; effs.Add "sum2"; (+) a
         let sum3 a (b:int) c   = printfn "calculating"; effs.Add "sum3"; a + b + c
         let sum4 a b c d : int = printfn "calculating"; effs.Add "sum4"; a + b + c + d

tests/FSharpPlusFable.Tests/FSharpTests/General/Alternative.fs

@@ -128,4 +128,4 @@ let alternative = testList "Alternative" [
         #endif
     )
 #endif
-]
+    ]

tests/FSharpPlusFable.Tests/FSharpTests/General/Applicative.fs

@@ -115,4 +115,4 @@ let applicative = testList "Applicative" [
         let r3 = lift2 (+) a3 b3
         Assert.AreEqual ("Here's the state SHere's the other state S", (ReaderT.run r3 "S" |> Async.RunSynchronously)))
     #endif
-]
+    ]

tests/FSharpPlusFable.Tests/FSharpTests/General/Collections.fs

@@ -261,5 +261,5 @@ let collections = testList "Collections" [
 
         let m = choose Some ((ofSeq :seq<_*_> -> Map<_,_>) (seq ["a", 1; "b", 2]))
         Assert.IsInstanceOf<Option<Map<string,int>>> (Some m))
-   #endif
-]
+    #endif
+    ]

tests/FSharpPlusFable.Tests/FSharpTests/General/Foldable.fs

@@ -337,5 +337,5 @@ let foldable = testList "Foldable" [
         equal None sb'
         ())
 #endif
-]
+    ]