Fix: Don't duplicate newline between recursive types

src/Fantomas.Tests/TypeDeclarationTests.fs

@@ -904,4 +904,100 @@ type C'() =
     |> should equal """
 type C'() =
     member _.M() = ()
+"""
+
+[<Test>]
+let ``don't add additional newlines between recursive type declarations, 520`` () =
+    formatSourceString false """module Game
+
+type Details =
+    { Name: string
+      Description: string }
+
+type Item =
+    { Details: Details }
+
+type Exit =
+    | Passable of Details * desitnation: Room
+    | Locked of Details * key: Item * next: Exit
+    | NoExit of Details option
+
+and Exits =
+    { North: Exit
+      South: Exit
+      East: Exit
+      West: Exit }
+
+and Room =
+    { Details: Details
+      Items: Item list
+      Exits: Exits }
+"""  config
+    |> prepend newline
+    |> should equal """
+module Game
+
+type Details =
+    { Name: string
+      Description: string }
+
+type Item =
+    { Details: Details }
+
+type Exit =
+    | Passable of Details * desitnation: Room
+    | Locked of Details * key: Item * next: Exit
+    | NoExit of Details option
+
+and Exits =
+    { North: Exit
+      South: Exit
+      East: Exit
+      West: Exit }
+
+and Room =
+    { Details: Details
+      Items: Item list
+      Exits: Exits }
+"""
+
+[<Test>]
+let ``don't add additional newlines between recursive type declarations with attributes, 520`` () =
+    formatSourceString false """module Game
+
+type Exit =
+    | Passable of Details * desitnation: Room
+    | Locked of Details * key: Item * next: Exit
+    | NoExit of Details option
+
+and Exits =
+    { North: Exit
+      South: Exit
+      East: Exit
+      West: Exit }
+
+and [<Marker()>] Room =
+    { Details: Details
+      Items: Item list
+      Exits: Exits }
+"""  config
+    |> prepend newline
+    |> should equal """
+module Game
+
+type Exit =
+    | Passable of Details * desitnation: Room
+    | Locked of Details * key: Item * next: Exit
+    | NoExit of Details option
+
+and Exits =
+    { North: Exit
+      South: Exit
+      East: Exit
+      West: Exit }
+
+and [<Marker>] Room =
+    { Details: Details
+      Items: Item list
+      Exits: Exits }
 """

src/Fantomas/CodePrinter.fs

@@ -338,9 +338,9 @@ and genModuleDecl astContext node =
             match List.tryHead ts with
             | Some tsh -> sepNln +> sepNlnConsideringTriviaContentBefore tsh.Range
             | None -> rep 2 sepNln
-        
+
         genTypeDefn { astContext with IsFirstChild = true } t 
-        +> colPre sepTs (rep 2 sepNln) ts (genTypeDefn { astContext with IsFirstChild = false })
+        +> colPreEx sepTs (fun (ty: SynTypeDefn) -> sepNln +> sepNlnConsideringTriviaContentBefore ty.Range) ts (genTypeDefn { astContext with IsFirstChild = false })
     | md ->
         failwithf "Unexpected module declaration: %O" md
     |> genTrivia node.Range

src/Fantomas/Context.fs

@@ -286,6 +286,10 @@ let internal colPre f2 f1 (c : seq<'T>) f (ctx : Context) =
     if Seq.isEmpty c then ctx
     else col f1 c f (f2 ctx)
 
+let internal colPreEx f2 f1 (c : seq<'T>) f (ctx : Context) =
+    if Seq.isEmpty c then ctx
+    else colEx f1 c f (f2 ctx)
+
 /// If there is a value, apply f and f' accordingly, otherwise do nothing
 let internal opt (f' : Context -> _) o f (ctx : Context) =
     match o with