Merge pull request #3230 from nojaf/fix-3098

Fix empty array/list trivia indentation in Stroustrup style

Author: nojaf

CHANGELOG.md

@@ -7,6 +7,7 @@
 - End of line comments after infix operators are preserved correctly. [#2287](https://github.com/fsprojects/fantomas/issues/2287)
 - Lambda closing parenthesis in chained method calls is no longer placed on its own line when `MultiLineLambdaClosingNewline` is enabled. [#2553](https://github.com/fsprojects/fantomas/issues/2553)
 - Long `&` (AND) patterns now break across multiple lines to respect max line length. [#1780](https://github.com/fsprojects/fantomas/issues/1780)
+- Empty array with trivia inside now has correct indentation in Stroustrup style. [#3098](https://github.com/fsprojects/fantomas/issues/3098)
 
 ## [8.0.0-alpha-002] - 2025-12-15
 

src/Fantomas.Core.Tests/Stroustrup/SynBindingValueExpressionTests.fs

@@ -832,3 +832,39 @@ let list =
     // comment
     ]
 """
+
+[<Test>]
+let ``empty array with blank line inside, 3098`` () =
+    formatSourceString
+        """
+let myArray = [|
+  
+  |]
+"""
+        config
+    |> prepend newline
+    |> should
+        equal
+        """
+let myArray = [|
+
+    |]
+"""
+
+[<Test>]
+let ``empty array with comment inside, 3098`` () =
+    formatSourceString
+        """
+let myArray2 = [|
+  // Some comment
+  |]
+"""
+        config
+    |> prepend newline
+    |> should
+        equal
+        """
+let myArray2 = [|
+    // Some comment
+    |]
+"""

src/Fantomas.Core/CodePrinter.fs

@@ -1778,7 +1778,20 @@ let genRecord smallRecordExpr multilineRecordExpr (node: ExprRecordBaseNode) ctx
 
 let genArrayOrList (preferMultilineCramped: bool) (node: ExprArrayOrListNode) =
     if node.Elements.IsEmpty then
-        genSingleTextNode node.Opening +> genSingleTextNode node.Closing |> genNode node
+        fun ctx ->
+            (genSingleTextNode node.Opening
+             +> (fun afterOpeningCtx ->
+                 // When the closing bracket has trivia (blank lines, comments) and we are using Stroustrup style,
+                 // the trivia needs to be indented inside the brackets. See 3098.
+                 if
+                     node.Closing.HasContentBefore
+                     && afterOpeningCtx.Config.MultilineBracketStyle = Stroustrup
+                 then
+                     (indent +> genSingleTextNode node.Closing +> unindent) afterOpeningCtx
+                 else
+                     (genSingleTextNode node.Closing) afterOpeningCtx)
+             |> genNode node)
+                ctx
     else
         let smallExpression =
             genSingleTextNode node.Opening