Idempotency problem when using lower MaxLineLength than default and f…

…antomas needs to split lines

 Fixes #2176

src/Fantomas.Tests/ComputationExpressionTests.fs

@@ -2436,3 +2436,42 @@ async {
     return model.Prop
 }
 """
+
+[<Test>]
+let ``Idempotency problem when using lower MaxLineLength than default, 2176`` () =
+    formatSourceString
+        false
+        """
+namespace FSX.Infrastructure
+
+module Unix =
+
+    let GrabTheFirstStringBeforeTheFirstColon (lines: seq<string>) =
+        seq {
+            for line in lines do
+                yield
+                    (line.Split(
+                        [| ":" |],
+                        StringSplitOptions.RemoveEmptyEntries
+                    )).[0]
+        }
+"""
+        { config with MaxLineLength = 80 }
+    |> prepend newline
+    |> should
+        equal
+        """
+namespace FSX.Infrastructure
+
+module Unix =
+
+    let GrabTheFirstStringBeforeTheFirstColon (lines: seq<string>) =
+        seq {
+            for line in lines do
+                yield
+                    (line.Split(
+                        [| ":" |],
+                        StringSplitOptions.RemoveEmptyEntries
+                    )).[0]
+        }
+"""

src/Fantomas/CodePrinter.fs

@@ -2453,7 +2453,12 @@ and genExpr astContext synExpr ctx =
 
             expressionFitsOnRestOfLine (short +> idx) (long +> idx)
         | DotIndexedGet (objectExpr, indexArgs) ->
-            addParenIfAutoNln objectExpr (genExpr astContext)
+            let isParen =
+                match objectExpr with
+                | Paren _ -> false
+                | _ -> true
+
+            ifElse isParen (addParenIfAutoNln objectExpr (genExpr astContext)) (genExpr astContext objectExpr)
             -- "."
             +> sepOpenLFixed
             +> genExpr astContext indexArgs