Fix problem with empty nested module generation (#2729)

fsprojects · Jan 19, 2023 · 959e49b · 959e49b
1 parent a6ecc25
commit 959e49b
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -4,6 +4,7 @@
 
 ### Fixed
 * Optional constructor arguments are lost. [#2718](https://github.com/fsprojects/fantomas/issues/2718)
+* Empty nested module. [#2721](https://github.com/fsprojects/fantomas/issues/2721~~~~)
 
 ## [5.2.0-alpha-012] - 2023-01-14
 

diff --git a/src/Fantomas.Core.Tests/ModuleTests.fs b/src/Fantomas.Core.Tests/ModuleTests.fs
@@ -1052,3 +1052,20 @@ module Ionide.VSCode.FSharp
 
 open global.Node.ChildProcess
 """
+
+[<Test>]
+let ``empty nested module, 2721`` () =
+    formatSourceString
+        true
+        """
+module Graph =
+    begin end
+"""
+        config
+    |> prepend newline
+    |> should
+        equal
+        """
+module Graph =
+    begin end
+"""
diff --git a/src/Fantomas.Core/CodePrinter.fs b/src/Fantomas.Core/CodePrinter.fs
@@ -3591,8 +3591,12 @@ let genModuleDecl (md: ModuleDecl) =
         +> sepSpace
         +> genSingleTextNode node.Equals
         +> indentSepNlnUnindent (
-            colWithNlnWhenMappedNodeIsMultiline false ModuleDecl.Node genModuleDecl node.Declarations
+            ifElse
+                (List.isEmpty node.Declarations)
+                (!- "begin end")
+                (colWithNlnWhenMappedNodeIsMultiline false ModuleDecl.Node genModuleDecl node.Declarations)
         )
+
         |> genNode (ModuleDecl.Node md)
     | ModuleDecl.TypeDefn td -> genTypeDefn td
     | ModuleDecl.Val node -> genVal node None