From 622ea8c109d32f90353eb036c78640115e7d85f8 Mon Sep 17 00:00:00 2001
From: piegames <git@piegames.de>
Date: Mon, 2 Dec 2024 23:24:01 +0100
Subject: [PATCH] Fix absorbtion of empty attrsets with newline

Fixes #253
---
 src/Nixfmt/Pretty.hs            |  6 ++++++
 test/diff/attr_set/in.nix       | 17 +++++++++++++++++
 test/diff/attr_set/out-pure.nix |  9 +++++++++
 test/diff/attr_set/out.nix      | 23 +++++++++++++++++++++++
 4 files changed, 55 insertions(+)

diff --git a/src/Nixfmt/Pretty.hs b/src/Nixfmt/Pretty.hs
index 1f03c822..4f99661c 100644
--- a/src/Nixfmt/Pretty.hs
+++ b/src/Nixfmt/Pretty.hs
@@ -540,6 +540,12 @@ isAbsorbable (Path _) = True
 -- Non-empty sets and lists
 isAbsorbable (Set _ _ (Items (_ : _)) _) = True
 isAbsorbable (List _ (Items (_ : _)) _) = True
+-- Empty sets and lists if they have a line break
+-- https://github.com/NixOS/nixfmt/issues/253
+isAbsorbable (Set _ (Ann{sourceLine = line1}) (Items []) (Ann{sourceLine = line2}))
+  | line1 /= line2 = True
+isAbsorbable (List (Ann{sourceLine = line1}) (Items []) (Ann{sourceLine = line2}))
+  | line1 /= line2 = True
 isAbsorbable (Parenthesized (LoneAnn _) (Term t) _) = isAbsorbable t
 isAbsorbable _ = False
 
diff --git a/test/diff/attr_set/in.nix b/test/diff/attr_set/in.nix
index e9ca7d84..abc8b304 100644
--- a/test/diff/attr_set/in.nix
+++ b/test/diff/attr_set/in.nix
@@ -274,4 +274,21 @@
         pkgs.xorg.fontadobe75dpi
       ];
   }
+  # Regression https://github.com/NixOS/nixfmt/issues/253
+  {
+    foo1 = {
+    };
+    foo2 = bar {
+    };
+    foo3 = bar {
+    } {
+    };
+    foo4 = [
+    ];
+    foo5 = bar [
+    ];
+    foo6 = bar [
+    ] [
+    ];
+  }
 ]
diff --git a/test/diff/attr_set/out-pure.nix b/test/diff/attr_set/out-pure.nix
index f28d2e25..c4b9cf21 100644
--- a/test/diff/attr_set/out-pure.nix
+++ b/test/diff/attr_set/out-pure.nix
@@ -378,4 +378,13 @@
         pkgs.xorg.fontadobe75dpi
       ];
   }
+  # Regression https://github.com/NixOS/nixfmt/issues/253
+  {
+    foo1 = { };
+    foo2 = bar { };
+    foo3 = bar { } { };
+    foo4 = [ ];
+    foo5 = bar [ ];
+    foo6 = bar [ ] [ ];
+  }
 ]
diff --git a/test/diff/attr_set/out.nix b/test/diff/attr_set/out.nix
index 7b52a916..bd47e960 100644
--- a/test/diff/attr_set/out.nix
+++ b/test/diff/attr_set/out.nix
@@ -381,4 +381,27 @@
         pkgs.xorg.fontadobe75dpi
       ];
   }
+  # Regression https://github.com/NixOS/nixfmt/issues/253
+  {
+    foo1 = {
+    };
+    foo2 = bar {
+    };
+    foo3 =
+      bar
+        {
+        }
+        {
+        };
+    foo4 = [
+    ];
+    foo5 = bar [
+    ];
+    foo6 =
+      bar
+        [
+        ]
+        [
+        ];
+  }
 ]