From 5014219a2c8486ddc0ae6945fafa5157e65a15c9 Mon Sep 17 00:00:00 2001
From: prql-bot <107324867+prql-bot@users.noreply.github.com>
Date: Sun, 16 Aug 2026 06:44:43 +0000
Subject: [PATCH] test: assert `fmt` is idempotent in the integration queries

---
 prqlc/prqlc/tests/integration/queries.rs | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/prqlc/prqlc/tests/integration/queries.rs b/prqlc/prqlc/tests/integration/queries.rs
index 48409a12552f..835107ffc779 100644
--- a/prqlc/prqlc/tests/integration/queries.rs
+++ b/prqlc/prqlc/tests/integration/queries.rs
@@ -128,8 +128,11 @@ mod fmt {
             assert_snapshot!(test_name, &formatted, &prql)
         });
 
-        // Check the formatted queries can still compile
-        prqlc::prql_to_pl(&formatted).unwrap();
+        // Formatting is idempotent: re-parsing & re-formatting the output must
+        // reproduce it exactly. This also covers the weaker property that the
+        // formatted query still parses.
+        let reformatted = prqlc::pl_to_prql(&prqlc::prql_to_pl(&formatted).unwrap()).unwrap();
+        similar_asserts::assert_eq!(formatted, reformatted);
     }
 }