From 182882b9cb806e3e0c71de08f6853827b76027bd Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bartek=20Iwa=C5=84czuk?= <biwanczuk@gmail.com>
Date: Tue, 2 Jun 2026 09:36:38 +0200
Subject: [PATCH] fix: stable formatting for conditional expression as if/else
 body

A single-statement if/else body that is a conditional (ternary) expression
could format differently on each run: when the inline form exceeds the line
width, braces are added and the body moves to its own indented line, where the
ternary then fits on one line, but it was being wrapped based on the pre-brace
column. This left the formatter producing different output on the next run
("Formatting not stable").

Wrap the single non-block statement body in a new_line_group so its line-break
decisions are re-measured at the body's final indentation, matching how binary
and call expressions already behave (which were already stable).
---
 src/generation/generate.rs                     |  4 ++--
 ...Deno_ConditionalExpressionStatementBody.txt | 18 ++++++++++++++++++
 2 files changed, 20 insertions(+), 2 deletions(-)
 create mode 100644 tests/specs/deno/Deno_ConditionalExpressionStatementBody.txt

diff --git a/src/generation/generate.rs b/src/generation/generate.rs
index 7fb3a332f..0cc27b50c 100644
--- a/src/generation/generate.rs
+++ b/src/generation/generate.rs
@@ -8854,13 +8854,13 @@ fn gen_conditional_brace_body<'a>(opts: GenConditionalBraceBodyOptions<'a>, cont
       items
     }));
   } else {
-    items.extend(ir_helpers::with_indent({
+    items.extend(ir_helpers::with_indent(ir_helpers::new_line_group({
       let mut items = PrintItems::new();
       let body_node_range = opts.body_node.range();
       items.extend(gen_node(opts.body_node, context));
       items.extend(gen_trailing_comments(&body_node_range, context));
       items
-    }));
+    })));
   }
 
   items.push_line_and_column(end_statements_lc);
diff --git a/tests/specs/deno/Deno_ConditionalExpressionStatementBody.txt b/tests/specs/deno/Deno_ConditionalExpressionStatementBody.txt
new file mode 100644
index 000000000..cb9a27eb0
--- /dev/null
+++ b/tests/specs/deno/Deno_ConditionalExpressionStatementBody.txt
@@ -0,0 +1,18 @@
+~~ deno: true ~~
+== should keep a conditional expression body stable when braces are added (not re-wrap the ternary) ==
+function w(n) {
+  if ("play" === n) {
+    var w = 1;
+    play({ ids: [b] });
+  } else if ("queue" === n) playing() ? queue({ ids: [b] }) : queue({ ids: [b] });
+}
+
+[expect]
+function w(n) {
+  if ("play" === n) {
+    var w = 1;
+    play({ ids: [b] });
+  } else if ("queue" === n) {
+    playing() ? queue({ ids: [b] }) : queue({ ids: [b] });
+  }
+}