Preserve trivia after attributes before name of nested module. Fixes f…

…sprojects#2016. (fsprojects#2020)

src/Fantomas.Tests/AttributeTests.fs

@@ -988,3 +988,58 @@ let x: int = 99
 // bar again, cuz why not
 let x: int = 99
 """
+
+[<Test>]
+let ``comment between attribute and nested module, 2016`` () =
+    formatSourceString
+        false
+        """
+[<AutoOpen>]
+// Having members as extensions gives them lower priority in
+// overload resolution and allows skipping more type annotations.
+module AsyncOptionCEExtensions =
+
+    type AsyncOptionBuilder with
+        member inline __.Source(s: #seq<_>) = s
+"""
+        config
+    |> prepend newline
+    |> should
+        equal
+        """
+[<AutoOpen>]
+// Having members as extensions gives them lower priority in
+// overload resolution and allows skipping more type annotations.
+module AsyncOptionCEExtensions =
+
+    type AsyncOptionBuilder with
+        member inline __.Source(s: #seq<_>) = s
+"""
+
+[<Test>]
+let ``comment between attribute and nested module, signature file`` () =
+    formatSourceString
+        true
+        """
+[<AutoOpen>]
+// Having members as extensions gives them lower priority in
+// overload resolution and allows skipping more type annotations.
+module AsyncOptionCEExtensions =
+
+    type AsyncOptionBuilder with
+        member inline Source : string -> string
+
+"""
+        config
+    |> prepend newline
+    |> should
+        equal
+        """
+[<AutoOpen>]
+// Having members as extensions gives them lower priority in
+// overload resolution and allows skipping more type annotations.
+module AsyncOptionCEExtensions =
+
+    type AsyncOptionBuilder with
+        member inline Source: string -> string
+"""

src/Fantomas/AstExtensions.fs

@@ -46,6 +46,22 @@ type SynField with
         | SynField (attributes = _ :: _; idOpt = None) -> None
         | SynField (attributes = attrs; idOpt = Some ident) -> hasLinesBetweenAttributesAndFirstNode attrs ident.idRange
 
+type SynModuleDecl with
+    member this.AfterAttributesBeforeNestedModuleName: Range option =
+        match this with
+        | SynModuleDecl.NestedModule(moduleInfo = SynComponentInfo(attributes = [])) -> None
+        | SynModuleDecl.NestedModule(moduleInfo = SynComponentInfo (attributes = attrs; longId = lid :: _)) ->
+            hasLinesBetweenAttributesAndFirstNode attrs lid.idRange
+        | _ -> None
+
+type SynModuleSigDecl with
+    member this.AfterAttributesBeforeNestedModuleName: Range option =
+        match this with
+        | SynModuleSigDecl.NestedModule(moduleInfo = SynComponentInfo(attributes = [])) -> None
+        | SynModuleSigDecl.NestedModule(moduleInfo = SynComponentInfo (attributes = attrs; longId = lid :: _)) ->
+            hasLinesBetweenAttributesAndFirstNode attrs lid.idRange
+        | _ -> None
+
 // TODO: Remove when https://github.com/dotnet/fsharp/pull/12441 is part of FCS
 type SynExceptionDefnRepr with
     member this.FullRange: range =

src/Fantomas/AstTransformer.fs

@@ -40,7 +40,13 @@ module private Ast =
                     decls |> List.map visit
 
                 let finalContinuation (nodes: TriviaNodeAssigner list list) : TriviaNodeAssigner list =
+                    let afterAttributesBeforeNestedModule =
+                        ast.AfterAttributesBeforeNestedModuleName
+                        |> Option.map (mkNode SynModuleDecl_NestedModule_AfterAttributesBeforeModuleName)
+                        |> Option.toList
+
                     [ mkNode SynModuleDecl_NestedModule range
+                      yield! afterAttributesBeforeNestedModule
                       yield! visitSynComponentInfo sci
                       yield! (List.collect id nodes) ]
                     |> finalContinuation
@@ -1349,7 +1355,13 @@ module private Ast =
                     List.map visit decls
 
                 let finalContinuation (nodes: TriviaNodeAssigner list list) : TriviaNodeAssigner list =
+                    let afterAttributesBeforeNestedModule =
+                        ast.AfterAttributesBeforeNestedModuleName
+                        |> Option.map (mkNode SynModuleSigDecl_NestedModule_AfterAttributesBeforeModuleName)
+                        |> Option.toList
+
                     [ yield mkNode SynModuleSigDecl_NestedModule range
+                      yield! afterAttributesBeforeNestedModule
                       yield! visitSynComponentInfo sci
                       yield! (List.collect id nodes) ]
                     |> finalContinuation

src/Fantomas/CodePrinter.fs

@@ -383,6 +383,9 @@ and genModuleDecl astContext (node: SynModuleDecl) =
     | NestedModule (ats, px, ao, s, isRecursive, mds) ->
         genPreXmlDoc px
         +> genAttributes astContext ats
+        +> genAfterAttributesBefore
+            SynModuleDecl_NestedModule_AfterAttributesBeforeModuleName
+            node.AfterAttributesBeforeNestedModuleName
         +> (!- "module ")
         +> opt sepSpace ao genAccess
         +> ifElse isRecursive (!- "rec ") sepNone
@@ -419,7 +422,11 @@ and genSigModuleDecl astContext node =
     | SigModuleAbbrev (s1, s2) -> !- "module " -- s1 +> sepEq +> sepSpace -- s2
     | SigNamespaceFragment m -> failwithf "NamespaceFragment is not supported yet: %O" m
     | SigNestedModule (ats, px, ao, s, mds) ->
-        genPreXmlDoc px +> genAttributes astContext ats
+        genPreXmlDoc px
+        +> genAttributes astContext ats
+        +> genAfterAttributesBefore
+            SynModuleSigDecl_NestedModule_AfterAttributesBeforeModuleName
+            node.AfterAttributesBeforeNestedModuleName
         -- "module "
         +> opt sepSpace ao genAccess
         -- s

src/Fantomas/TriviaTypes.fs

@@ -105,6 +105,7 @@ type FsAstType =
     //    | SynModuleOrNamespace_NamedModule
     | SynModuleDecl_ModuleAbbrev
     | SynModuleDecl_NestedModule
+    | SynModuleDecl_NestedModule_AfterAttributesBeforeModuleName
     | SynModuleDecl_Let
     | SynModuleDecl_DoExpr
     | SynModuleDecl_Types
@@ -343,6 +344,7 @@ type FsAstType =
 //    | SynModuleOrNamespaceSig_NamedModule
     | SynModuleSigDecl_ModuleAbbrev
     | SynModuleSigDecl_NestedModule
+    | SynModuleSigDecl_NestedModule_AfterAttributesBeforeModuleName
     | SynModuleSigDecl_Types
     | SynModuleSigDecl_Open
     | SynModuleSigDecl_OpenType