From e39b2fae3aad9fc64288cb73b29a0d913f94ce4a Mon Sep 17 00:00:00 2001
From: Silvan Mosberger <silvan.mosberger@tweag.io>
Date: Fri, 30 Aug 2024 01:50:18 +0200
Subject: [PATCH] Fix selections getting expanded too liberally

---
 src/Nixfmt/Pretty.hs            | 7 ++++++-
 test/correct/regression-207.nix | 5 +++++
 2 files changed, 11 insertions(+), 1 deletion(-)
 create mode 100644 test/correct/regression-207.nix

diff --git a/src/Nixfmt/Pretty.hs b/src/Nixfmt/Pretty.hs
index 120ef92b..504cd75d 100644
--- a/src/Nixfmt/Pretty.hs
+++ b/src/Nixfmt/Pretty.hs
@@ -375,7 +375,12 @@ instance Pretty Parameter where
 --    then start on a new line instead".
 prettyApp :: Bool -> Doc -> Bool -> Expression -> Expression -> Doc
 prettyApp indentFunction pre hasPost f a =
-  let absorbApp (Application f' a') = group' Transparent (absorbApp f') <> line <> nest (group' Priority a')
+  let
+      -- This is very hacky, but selections shouldn't be in a priority group,
+      -- because if they get expanded before anything else,
+      -- only the `.`-and-after part gets to a new line, which looks very odd
+      absorbApp (Application f' a'@(Term Selection{})) = group' Transparent (absorbApp f') <> line <> nest (group' RegularG a')
+      absorbApp (Application f' a') = group' Transparent (absorbApp f') <> line <> nest (group' Priority a')
       absorbApp expr
         | indentFunction && null comment' = nest $ group' RegularG $ line' <> pretty expr
         | otherwise = pretty expr
diff --git a/test/correct/regression-207.nix b/test/correct/regression-207.nix
new file mode 100644
index 00000000..3213e9e7
--- /dev/null
+++ b/test/correct/regression-207.nix
@@ -0,0 +1,5 @@
+{
+  rust-channel-of-version =
+    assertEq (rustChannelOf { channel = "1.48.0"; }).rustc
+      stable."1.48.0".rustc;
+}