Check if we just wrote a DotLambda before deciding on space before parens, fix 3050

CHANGELOG.md

@@ -5,6 +5,7 @@
 ### Fixed
 * Equals sign should only be on same line if last tuple is multiline. [#3040](https://github.com/fsprojects/fantomas/issues/3040)
 * Return type should go on next line. [#3041](https://github.com/fsprojects/fantomas/issues/3041)
+* Idempotency problem when _.Property shorthand. [#3050](https://github.com/fsprojects/fantomas/issues/3050)
 
 ## 6.3.0-alpha-007 - 2024-01-27
 

src/Fantomas.Core.Tests/DotLambdaTests.fs

@@ -59,3 +59,48 @@ let c = _.foo().Length
         """
 let c = _.foo().Length
 """
+
+[<Test>]
+let ``idempotency problem when _.Property shorthand, 3050`` () =
+    formatSourceString
+        """
+"ABC" |> _.ToLower()
+"""
+        { config with
+            SpaceBeforeUppercaseInvocation = true }
+    |> prepend newline
+    |> should
+        equal
+        """
+"ABC" |> _.ToLower()
+"""
+
+[<Test>]
+let ``idempotency problem when _.property shorthand lowercase, 3050`` () =
+    formatSourceString
+        """
+"ABC" |> _.toLower()
+"""
+        { config with
+            SpaceBeforeLowercaseInvocation = true }
+    |> prepend newline
+    |> should
+        equal
+        """
+"ABC" |> _.toLower()
+"""
+
+[<Test>]
+let ``idempotency problem when _.property shorthand quoted, 3050`` () =
+    formatSourceString
+        """
+"ABC" |> _.``to Lower``()
+"""
+        { config with
+            SpaceBeforeLowercaseInvocation = true }
+    |> prepend newline
+    |> should
+        equal
+        """
+"ABC" |> _.``to Lower``()
+"""

src/Fantomas.Core/CodePrinter.fs

@@ -2519,8 +2519,10 @@ let sepSpaceBeforeParenInFuncInvocation (functionExpr: Expr) (argExpr: Expr) ctx
     | Expr.DotLambda _, _ -> ctx
     | Expr.Constant _, _ -> sepSpace ctx
     | ParenExpr _, _ -> sepSpace ctx
-    | UppercaseExpr, ParenExpr _ -> onlyIf ctx.Config.SpaceBeforeUppercaseInvocation sepSpace ctx
-    | LowercaseExpr, ParenExpr _ -> onlyIf ctx.Config.SpaceBeforeLowercaseInvocation sepSpace ctx
+    | UppercaseExpr, ParenExpr _ ->
+        onlyIf (ctx.Config.SpaceBeforeUppercaseInvocation && not (lastWriteEventIsDotLambda ctx)) sepSpace ctx
+    | LowercaseExpr, ParenExpr _ ->
+        onlyIf (ctx.Config.SpaceBeforeLowercaseInvocation && not (lastWriteEventIsDotLambda ctx)) sepSpace ctx
     | Expr.Ident _, Expr.Ident _ -> sepSpace ctx
     | _ -> sepSpace ctx
 

src/Fantomas.Core/Context.fs

@@ -338,6 +338,16 @@
         | _ -> false)
     |> Option.defaultValue false
 
+let lastWriteEventIsDotLambda ctx =
+    ctx.WriterEvents
+    |> Queue.rev
+    |> List.ofSeq
+    |> function
+        | WriterEvent.Write f :: Write "." :: Write "_" :: _ ->
+            String.isNotNullOrWhitespace f
+            && (Char.IsLetter(f[0]) || (f.StartsWith("``") && f.EndsWith("``")))
+        | _ -> false
+
 let (|EmptyHashDefineBlock|_|) (events: WriterEvent array) =
     match Array.tryHead events, Array.tryLast events with
     | Some(CommentOrDefineEvent _), Some(CommentOrDefineEvent _) ->

src/Fantomas.Core/Context.fsi

@@ -73,6 +73,7 @@ val hasWriteBeforeNewlineContent: ctx: Context -> bool
 val dump: isSelection: bool -> ctx: Context -> FormatResult
 val dumpAndContinue: ctx: Context -> Context
 val lastWriteEventIsNewline: ctx: Context -> bool
+val lastWriteEventIsDotLambda: ctx: Context -> bool
 
 /// Indent one more level based on configuration
 val indent: ctx: Context -> Context