Fix index-without-dot followed by application arguments

CHANGELOG.md

@@ -1,5 +1,12 @@
 # Changelog
 
+## [8.0.0-alpha-005] - 2026-03-09
+
+### Fixed
+
+- Closing `>` in nested multiline generic type applications violates offside rule. [#3243](https://github.com/fsprojects/fantomas/issues/3243)
+- Index-without-dot syntax followed by application arguments was inconsistently formatted. [#3259](https://github.com/fsprojects/fantomas/pull/3259)
+
 ## [8.0.0-alpha-004] - 2026-03-07
 
 ### Changed
@@ -8,7 +15,6 @@
 
 ### Fixed
 
-- Closing `>` in nested multiline generic type applications violates offside rule. [#3243](https://github.com/fsprojects/fantomas/issues/3243)
 - Lambda in non-last record field is now parenthesized when record is collapsed to single line to avoid producing invalid code. [#3246](https://github.com/fsprojects/fantomas/issues/3246)
 - `fsharp_newline_before_multiline_computation_expression = false` no longer produces invalid code when the CE builder's argument list wraps to multiple lines. [#3155](https://github.com/fsprojects/fantomas/issues/3155)
 

src/Fantomas.Core.Tests/IndexSyntaxTests.fs

@@ -273,3 +273,45 @@ inventory["Oranges"] // raises an exception if not found
 inventory.["Apples"] // raises an exception if not found
 nestedInventory["Oranges"][23] // raises an exception if not found
 """
+
+[<Test>]
+let ``index without dot followed by application argument`` () =
+    formatSourceString
+        """
+prepConfigs[1] host
+"""
+        config
+    |> prepend newline
+    |> should
+        equal
+        """
+prepConfigs[1] host
+"""
+
+[<Test>]
+let ``index without dot followed by multiple application arguments`` () =
+    formatSourceString
+        """
+prepConfigs[1] host port
+"""
+        config
+    |> prepend newline
+    |> should
+        equal
+        """
+prepConfigs[1] host port
+"""
+
+[<Test>]
+let ``index without dot with spaces followed by multiple application arguments`` () =
+    formatSourceString
+        """
+prepConfigs[ 1 ] host days
+"""
+        config
+    |> prepend newline
+    |> should
+        equal
+        """
+prepConfigs[1] host days
+"""

src/Fantomas.Core/ASTTransformer.fs

@@ -631,6 +631,7 @@ let (|ConstNumberExpr|_|) =
 let (|App|_|) e =
     let rec visit expr continuation =
         match expr with
+        | IndexWithoutDot _ -> continuation (expr, Queue())
         | SynExpr.App(funcExpr = funcExpr; argExpr = argExpr) ->
             visit funcExpr (fun (head, xs: Queue<SynExpr>) ->
                 xs.Enqueue(argExpr)
@@ -1362,38 +1363,6 @@ let mkExpr (creationAide: CreationAide) (e: SynExpr) : Expr =
 
         ExprAppWithLambdaNode(mkExpr creationAide fe, [], stn "(" lpr, Choice2Of2 lambdaNode, stn ")" rpr, exprRange)
         |> Expr.AppWithLambda
-    | SynExpr.App(ExprAtomicFlag.NonAtomic,
-                  false,
-                  SynExpr.App(ExprAtomicFlag.Atomic,
-                              false,
-                              identifierExpr,
-                              SynExpr.ArrayOrListComputed(false, indexExpr, _),
-                              _),
-                  argExpr,
-                  _) ->
-        ExprNestedIndexWithoutDotNode(
-            mkExpr creationAide identifierExpr,
-            mkExpr creationAide indexExpr,
-            mkExpr creationAide argExpr,
-            exprRange
-        )
-        |> Expr.NestedIndexWithoutDot
-    | SynExpr.App(ExprAtomicFlag.NonAtomic,
-                  false,
-                  SynExpr.App(ExprAtomicFlag.NonAtomic,
-                              false,
-                              identifierExpr,
-                              (SynExpr.ArrayOrListComputed(isArray = false; expr = indexExpr) as indexArgExpr),
-                              _),
-                  argExpr,
-                  _) when (RangeHelpers.isAdjacentTo identifierExpr.Range indexArgExpr.Range) ->
-        ExprNestedIndexWithoutDotNode(
-            mkExpr creationAide identifierExpr,
-            mkExpr creationAide indexExpr,
-            mkExpr creationAide argExpr,
-            exprRange
-        )
-        |> Expr.NestedIndexWithoutDot
 
     | App(fe, args) ->
         ExprAppNode(mkExpr creationAide fe, List.map (mkExpr creationAide) args, exprRange)

src/Fantomas.Core/CodePrinter.fs

@@ -61,6 +61,7 @@ let rec (|UppercaseExpr|LowercaseExpr|) (expr: Expr) =
     | Expr.AppSingleParenArg node -> (|UppercaseExpr|LowercaseExpr|) node.FunctionExpr
     | Expr.Paren node -> (|UppercaseExpr|LowercaseExpr|) node.Expr
     | Expr.App node -> (|UppercaseExpr|LowercaseExpr|) node.FunctionExpr
+    | Expr.IndexWithoutDot node -> (|UppercaseExpr|LowercaseExpr|) node.Identifier
     | _ -> failwithf "cannot determine if Expr %A is uppercase or lowercase" expr
 
 let (|ParenExpr|_|) (e: Expr) =
@@ -1034,6 +1035,12 @@ let genExpr (e: Expr) =
 
         genAppLongIdentAndSingleParenArgExpr addSpace node
     // fn (a, b, c)
+    | Expr.AppSingleParenArg node when
+        (match node.FunctionExpr with
+         | Expr.IndexWithoutDot _ -> true
+         | _ -> false)
+        ->
+        (genExpr node.FunctionExpr +> genExpr node.ArgExpr) |> genNode node
     | Expr.AppSingleParenArg node ->
         let addSpace = sepSpaceBeforeParenInFuncInvocation node.FunctionExpr node.ArgExpr
         genAppSingleParenArgExpr addSpace node
@@ -2600,6 +2607,7 @@ let genAppWithLambda sep (node: ExprAppWithLambdaNode) =
 let sepSpaceBeforeParenInFuncInvocation (functionExpr: Expr) (argExpr: Expr) ctx =
     match functionExpr, argExpr with
     | Expr.DotLambda _, _ -> ctx
+    | Expr.IndexWithoutDot _, ParenExpr _ -> ctx
     | Expr.Constant _, _ -> sepSpace ctx
     | ParenExpr _, _ -> sepSpace ctx
     | UppercaseExpr, ParenExpr _ -> onlyIf ctx.Config.SpaceBeforeUppercaseInvocation sepSpace ctx