From 124eca6d97ab3d0b52e57867b78faf15a9365c22 Mon Sep 17 00:00:00 2001
From: piegames <git@piegames.de>
Date: Mon, 2 Dec 2024 23:33:56 +0100
Subject: [PATCH] Don't move trailing comments in let anymore

While this was initially introduced for good reasons, as can also be
seen in the diff, that code was written with documentation comments in
mind and not code comments. As per the bug report, the downsides were
deemed to high to keep it in

Fixes #259
---
 src/Nixfmt/Pretty.hs                | 22 ++--------------------
 test/diff/comment/out-pure.nix      |  2 +-
 test/diff/comment/out.nix           |  2 +-
 test/diff/idioms_lib_3/out-pure.nix |  2 +-
 test/diff/idioms_lib_3/out.nix      |  2 +-
 test/diff/let_in/out-pure.nix       |  4 ++--
 test/diff/let_in/out.nix            |  4 ++--
 7 files changed, 10 insertions(+), 28 deletions(-)

diff --git a/src/Nixfmt/Pretty.hs b/src/Nixfmt/Pretty.hs
index 4f99661c..f502609b 100644
--- a/src/Nixfmt/Pretty.hs
+++ b/src/Nixfmt/Pretty.hs
@@ -646,31 +646,13 @@ instance Pretty Expression where
       convertTrailing Nothing = []
       convertTrailing (Just (TrailingComment t)) = [LineComment (" " <> t)]
 
-      -- Extract detached comments at the bottom.
-      -- This uses a custom variant of span/spanJust/spanMaybe.
-      -- Note that this is a foldr which walks from the bottom, but the lists
-      -- are constructed in a way that they end up correct again.
-      (binderComments, bindersWithoutComments) =
-        foldr
-          ( \item (start, rest) -> case item of
-              (Comments inner)
-                | null rest ->
-                    -- Only move all non-empty-line trivia below the `in`
-                    let (comments, el) = break (== EmptyLine) (reverse inner)
-                    in (reverse comments : start, Comments (reverse el) : rest)
-              _ -> (start, item : rest)
-          )
-          ([], [])
-          (unItems binders)
-
       letPart = group $ pretty let_ <> hardline <> letBody
-      letBody = nest $ prettyItems (Items bindersWithoutComments)
+      letBody = nest $ prettyItems binders
       inPart =
         group $
           pretty in_
             <> hardline
-            -- Take our trailing and inject it between `in` and body
-            <> pretty (concat binderComments ++ preTrivia ++ convertTrailing trailComment)
+            <> pretty (preTrivia ++ convertTrailing trailComment)
             <> pretty expr
   pretty (Assert assert cond semicolon expr) =
     group $
diff --git a/test/diff/comment/out-pure.nix b/test/diff/comment/out-pure.nix
index 138f59c0..c8d87b6c 100644
--- a/test/diff/comment/out-pure.nix
+++ b/test/diff/comment/out-pure.nix
@@ -146,8 +146,8 @@
       #6
 
       d = 1;
+      #7
     in
-    #7
     d
   )
 
diff --git a/test/diff/comment/out.nix b/test/diff/comment/out.nix
index 138f59c0..c8d87b6c 100644
--- a/test/diff/comment/out.nix
+++ b/test/diff/comment/out.nix
@@ -146,8 +146,8 @@
       #6
 
       d = 1;
+      #7
     in
-    #7
     d
   )
 
diff --git a/test/diff/idioms_lib_3/out-pure.nix b/test/diff/idioms_lib_3/out-pure.nix
index 2c9c796e..d704f9a5 100644
--- a/test/diff/idioms_lib_3/out-pure.nix
+++ b/test/diff/idioms_lib_3/out-pure.nix
@@ -148,8 +148,8 @@ rec {
           [${mkSectionName sectName}]
         ''
         + toKeyValue { inherit mkKeyValue listsAsDuplicateKeys; } sectValues;
+      # map input to ini sections
     in
-    # map input to ini sections
     mapAttrsToStringsSep "\n" mkSection attrsOfAttrs;
 
   # Generate an INI-style config file from an attrset
diff --git a/test/diff/idioms_lib_3/out.nix b/test/diff/idioms_lib_3/out.nix
index 53474a65..2686bade 100644
--- a/test/diff/idioms_lib_3/out.nix
+++ b/test/diff/idioms_lib_3/out.nix
@@ -151,8 +151,8 @@ rec {
           [${mkSectionName sectName}]
         ''
         + toKeyValue { inherit mkKeyValue listsAsDuplicateKeys; } sectValues;
+      # map input to ini sections
     in
-    # map input to ini sections
     mapAttrsToStringsSep "\n" mkSection attrsOfAttrs;
 
   # Generate an INI-style config file from an attrset
diff --git a/test/diff/let_in/out-pure.nix b/test/diff/let_in/out-pure.nix
index 6870e5b3..c0774c93 100644
--- a/test/diff/let_in/out-pure.nix
+++ b/test/diff/let_in/out-pure.nix
@@ -65,9 +65,9 @@ let
     let
       b = 0;
 
+      # foo
+      # bar
     in
-    # foo
-    # bar
     # baz
     # qux
     null;
diff --git a/test/diff/let_in/out.nix b/test/diff/let_in/out.nix
index 6870e5b3..c0774c93 100644
--- a/test/diff/let_in/out.nix
+++ b/test/diff/let_in/out.nix
@@ -65,9 +65,9 @@ let
     let
       b = 0;
 
+      # foo
+      # bar
     in
-    # foo
-    # bar
     # baz
     # qux
     null;