Update space before colon to F# style guide (#1781)

* Update space before colon separator for values. Fixes #1773.

* Update documentation.

README.md

@@ -72,7 +72,7 @@ We use [BenchmarkDotNet](https://github.com/dotnet/BenchmarkDotNet) to collect d
 This project aims at formatting F# source files based on a given configuration.
 Fantomas will ensure correct indentation and consistent spacing between elements in the source files.
 We assume that the source files are *parsable by F# compiler* before feeding into the tool.
-Fantomas follows the formatting guideline being described in [A comprehensive guide to F# Formatting Conventions](docs/FormattingConventions.md).
+Fantomas follows two F# style guides: the [F# code formatting guidelines](https://docs.microsoft.com/en-us/dotnet/fsharp/style-guide/formatting) from Microsoft by default and the [G-Research F# code formatting guidelines](https://github.com/G-Research/fsharp-formatting-conventions) via various [settings](https://github.com/G-Research/fsharp-formatting-conventions/blob/master/.editorconfig).
 
 ## Use cases
 The project is developed with the following use cases in mind:

docs/Documentation.md

@@ -329,22 +329,22 @@ type Person() =
 
 ### fsharp_space_before_colon
 
-Add a space before `:`.
+Add a space before `:`. Please note that not every `:` is controlled by this setting.
 Default = false.
 
 `defaultConfig`
 
 ```fsharp
 type Point = { x: int; y: int }
-
-let update (msg: Msg) (model: Model): Model = model
+let myValue: int = 42 // See https://docs.microsoft.com/en-us/dotnet/fsharp/style-guide/formatting#right-pad-value-and-function-argument-type-annotations
+let update (msg: Msg) (model: Model) : Model = model // See https://docs.microsoft.com/en-us/dotnet/fsharp/style-guide/formatting#surround-return-type-annotations-with-white-space
 ```
 
 `{ defaultConfig with SpaceBeforeColon = true }`
 
 ```fsharp
 type Point = { x : int; y : int }
-
+let myValue : int = 42
 let update (msg : Msg) (model : Model) : Model = model
 ```
 

src/Fantomas.Tests/ClassTests.fs

@@ -265,7 +265,7 @@ and File(filename: string, containingFolder: Folder) =
         """
 type Folder(pathIn: string) =
     let path = pathIn
-    let filenameArray : string array = System.IO.Directory.GetFiles(path)
+    let filenameArray: string array = System.IO.Directory.GetFiles(path)
     member this.FileArray = Array.map (fun elem -> new File(elem, this)) filenameArray
 
 and File(filename: string, containingFolder: Folder) =

src/Fantomas.Tests/CommentTests.fs

@@ -51,7 +51,7 @@ let print_30_permut() =
 let print_30_permut () =
 
     /// declare and initialize
-    let permutation : int array =
+    let permutation: int array =
         Array.init
             n
             (fun i ->
@@ -80,7 +80,7 @@ let print_30_permut() =
 let print_30_permut () =
 
     /// declare and initialize
-    let permutation : int array =
+    let permutation: int array =
         Array.init
             n
             (fun (i, j) ->

src/Fantomas.Tests/CompilerDirectivesTests.fs

@@ -936,11 +936,11 @@ let ``module with nested directives`` () =
 #else
     [<Import("*", "react-dom")>]
 #endif
-    let ReactDom : IReactDom = jsNative
+    let ReactDom: IReactDom = jsNative
 
 #if !FABLE_REPL_LIB
     [<Import("default", "react-dom/server")>]
-    let ReactDomServer : IReactDomServer = jsNative
+    let ReactDomServer: IReactDomServer = jsNative
 #endif
 """
 
@@ -969,11 +969,11 @@ let ``module with nested directives, no defines`` () =
 #else
     [<Import("*", "react-dom")>]
 #endif
-    let ReactDom : IReactDom = jsNative
+    let ReactDom: IReactDom = jsNative
 
 #if !FABLE_REPL_LIB
     [<Import("default", "react-dom/server")>]
-    let ReactDomServer : IReactDomServer = jsNative
+    let ReactDomServer: IReactDomServer = jsNative
 #endif
 """
 
@@ -1002,7 +1002,7 @@ let ``module with nested directives, FABLE_REPL_LIB`` () =
 #else
 
 #endif
-    let ReactDom : IReactDom = jsNative
+    let ReactDom: IReactDom = jsNative
 
 #if !FABLE_REPL_LIB
 

src/Fantomas.Tests/ComputationExpressionTests.fs

@@ -1932,7 +1932,7 @@ let create: Highlighter =
     |> should
         equal
         """
-let create : Highlighter =
+let create: Highlighter =
     fun searchTerm ->
         let regex = searchTerm |> SearchTerm.toRegex
 
@@ -2024,7 +2024,7 @@ let result = ResultBuilder()
 
 let run r1 r2 r3 =
     // And here is our applicative!
-    let res1 : Result<int, string> =
+    let res1: Result<int, string> =
         result {
             let! a = r1
             and! b = r2

src/Fantomas.Tests/ControlStructureTests.fs

@@ -734,7 +734,7 @@ let foldi (folder: 'State -> int -> 'T -> 'State) (state: 'State) (array: 'T [])
         let folder =
             OptimizedClosures.FSharpFunc<_, _, _, _>.Adapt folder
 
-        let mutable state : 'State = state
+        let mutable state: 'State = state
         let len = array.Length
 
         for i = 0 to len - 1 do

src/Fantomas.Tests/Fantomas.Tests.fsproj

@@ -88,6 +88,7 @@
     <Compile Include="BlankLinesAroundNestedMultilineExpressions.fs" />
     <Compile Include="ColMultilineItemTests.fs" />
     <Compile Include="BarBeforeDiscriminatedUnionDeclarationTests.fs" />
+    <Compile Include="SpaceBeforeColonTests.fs" />
   </ItemGroup>
   <ItemGroup>
     <ProjectReference Include="..\Fantomas.Extras\Fantomas.Extras.fsproj" />

src/Fantomas.Tests/FunctionDefinitionTests.fs

@@ -154,7 +154,7 @@ let ``=foo hoo`` () = ()
 let ``-foo hoo`` () = ()
 let ``!foo hoo`` () : unit = ()
 let ``@foo hoo`` = ()
-let ``$foo hoo`` : unit = ()
+let ``$foo hoo``: unit = ()
 """
 
 [<Test>]
@@ -178,8 +178,8 @@ let ``let bindings with return types`` () =
         equal
         """
 let divide x y =
-    let stream : System.IO.FileStream = System.IO.File.Create("test.txt")
-    let writer : System.IO.StreamWriter = new System.IO.StreamWriter(stream)
+    let stream: System.IO.FileStream = System.IO.File.Create("test.txt")
+    let writer: System.IO.StreamWriter = new System.IO.StreamWriter(stream)
 
     try
         writer.WriteLine("test1")
@@ -1027,12 +1027,12 @@ let e<'t> : int = 8
     |> should
         equal
         """
-let a : int = 7
-let private b : string = ""
-let internal c : int = 8
+let a: int = 7
+let private b: string = ""
+let internal c: int = 8
 
 [<Foo>]
-let d : int = 9
+let d: int = 9
 
 let e<'t> : int = 8
 """
@@ -1111,20 +1111,20 @@ let e<'t> : int =
     |> should
         equal
         """
-let a : int =
+let a: int =
     // a comment makes things multiline
     7
 
-let private b : string =
+let private b: string =
     // a comment makes things multiline
     ""
 
-let internal c : int =
+let internal c: int =
     // a comment makes things multiline
     8
 
 [<Foo>]
-let d : int =
+let d: int =
     // a comment makes things multiline
     9
 

src/Fantomas.Tests/HashDirectiveTests.fs

@@ -81,7 +81,7 @@ open ASTViewer.Shared
 open FantomasTools.Client.ASTViewer.Model
 open Thoth.Json
 
-let decodeKeyValue : Decoder<obj> = fun _key jsonValue -> Ok jsonValue
+let decodeKeyValue: Decoder<obj> = fun _key jsonValue -> Ok jsonValue
 
 #nowarn "40"
 """

src/Fantomas.Tests/IfThenElseTests.fs

@@ -2203,7 +2203,7 @@ type internal Foo2 private () =
         equal
         """
 type internal Foo private () =
-    static member Bar : int option =
+    static member Bar: int option =
         if thing = 1 then
             printfn "hi"
         else if veryVeryVeryVeryVeryVeryVeryVeryVeryVeryVeryLong
@@ -2214,7 +2214,7 @@ type internal Foo private () =
             failwith ""
 
 type internal Foo2 private () =
-    static member Bar : int option =
+    static member Bar: int option =
         if thing = 1 then
             printfn "hi"
         else if veryVeryVeryVeryVeryVeryVeryVeryVeryVeryVeryLong

src/Fantomas.Tests/InterfaceTests.fs

@@ -586,7 +586,7 @@ and Bar =
         member this.Value = ()
 
         [<SomeAttribute>]
-        member this.ValueWithReturnType : unit = ()
+        member this.ValueWithReturnType: unit = ()
 
         [<SomeAttribute>]
         member this.SomeFunction(a: int) = 4 + a

src/Fantomas.Tests/LetBindingTests.fs

@@ -350,8 +350,8 @@ let someFun someReallyLoooooooooooooooongValue =
 
 [<Test>]
 let ``should keep space before :`` () =
-    formatSourceString false "let refl<'a> : Teq<'a, 'a> = Teq(id,   id)" config
-    |> fun formatted -> formatSourceString false formatted config
+    formatSourceString false "let refl<'a> : Teq<'a, 'a> = Teq(id,   id)" { config with SpaceBeforeColon = true }
+    |> fun formatted -> formatSourceString false formatted { config with SpaceBeforeColon = true }
     |> should
         equal
         "let refl<'a> : Teq<'a, 'a> = Teq(id, id)
@@ -1620,7 +1620,7 @@ let myFun (a: decimal) b c : decimal = a + b + c
     |> should
         equal
         """
-let expensiveToCompute : int = 0
+let expensiveToCompute: int = 0
 let myFun (a: decimal) b c : decimal = a + b + c
 """
 
@@ -1772,7 +1772,7 @@ type Viewport =
     |> should
         equal
         """
-let useGeolocation : unit
+let useGeolocation: unit
     -> {| latitude: float
           longitude: float
           loading: bool

src/Fantomas.Tests/ListTests.fs

@@ -1588,7 +1588,7 @@ let nestedList: obj list = [
     |> should
         equal
         """
-let nestedList : obj list =
+let nestedList: obj list =
     [ "11111111aaaaaaaaa"
       "22222222aaaaaaaaa"
       "33333333aaaaaaaaa"
@@ -1620,7 +1620,7 @@ let nestedList: obj list = [|
     |> should
         equal
         """
-let nestedList : obj list =
+let nestedList: obj list =
     [| "11111111aaaaaaaaa"
        "22222222aaaaaaaaa"
        "33333333aaaaaaaaa"
@@ -1651,7 +1651,7 @@ let nestedList: obj list = [|
     |> should
         equal
         """
-let nestedList : obj list =
+let nestedList: obj list =
     [| "11111111aaaaaaaaa"
        "22222222aaaaaaaaa"
        "33333333aaaaaaaaa"
@@ -1683,7 +1683,7 @@ let nestedList: obj list = [
     |> should
         equal
         """
-let nestedList : obj list =
+let nestedList: obj list =
     [ "11111111aaaaaaaaa"
       "22222222aaaaaaaaa"
       "33333333aaaaaaaaa"
@@ -1716,7 +1716,7 @@ let nestedList: obj list = [|
     |> should
         equal
         """
-let nestedList : obj list =
+let nestedList: obj list =
     [| "11111111aaaaaaaaa"
        "22222222aaaaaaaaa"
        "33333333aaaaaaaaa"
@@ -1956,7 +1956,7 @@ let choices : Foo list =
     |> should
         equal
         """
-let choices : Foo list =
+let choices: Foo list =
     [ yield! getMore 9
       yield
           // Test
@@ -1980,7 +1980,7 @@ let choices : Foo list =
     |> should
         equal
         """
-let choices : Foo list =
+let choices: Foo list =
     [ yield!
           // Test
           [ Foo 2 ] ]

src/Fantomas.Tests/RecordTests.fs

@@ -357,8 +357,8 @@ let ``anon record`` () =
     |> should
         equal
         """
-let r : {| Foo: int
-           Bar: string |} =
+let r: {| Foo: int
+          Bar: string |} =
     {| Foo = 123
        Bar = "" |}
 """
@@ -376,8 +376,8 @@ let ``anon record - struct`` () =
     |> should
         equal
         """
-let r : struct {| Foo: int
-                  Bar: string |} =
+let r: struct {| Foo: int
+                 Bar: string |} =
     struct {| Foo = 123
               Bar = "" |}
 """
@@ -1205,7 +1205,7 @@ type XX =
 type XX =
     { a: int
       b: int }
-    static member foo : int = 30
+    static member foo: int = 30
 """
 
 [<Test>]
@@ -1228,7 +1228,7 @@ type XX =
     { a: int
       b: int }
 
-    static member private foo : int = 30
+    static member private foo: int = 30
 """
 
 [<Test>]