From aa00a5a8c9ba7b74c2102b8dc7fc4c3ed58606d8 Mon Sep 17 00:00:00 2001
From: Alois Wohlschlager <alois1@gmx-topmail.de>
Date: Wed, 12 Jun 2024 19:42:38 +0200
Subject: [PATCH] libfetchers: represent unfetched submodules consistently

Unfetched submodules are included as empty directories in archives, so they end
up as such in the store when fetched in clean mode. Make sure the same happens
in dirty mode too. Fortunately, they are already correctly represented in the
ls-files output, so we just need to make sure to include the empty directory in
our filter.

Fixes: https://github.com/NixOS/nix/issues/6247
Change-Id: I60d06ff360cfa305d081b920838c893c06da801c
---
 src/libfetchers/git.cc                 | 2 +-
 tests/functional/fetchGitSubmodules.sh | 2 ++
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/libfetchers/git.cc b/src/libfetchers/git.cc
index 07cbc781c..2817fde23 100644
--- a/src/libfetchers/git.cc
+++ b/src/libfetchers/git.cc
@@ -232,7 +232,7 @@ std::pair<StorePath, Input> fetchFromWorkdir(ref<Store> store, Input & input, co
         if (S_ISDIR(st.st_mode)) {
             auto prefix = file + "/";
             auto i = files.lower_bound(prefix);
-            return i != files.end() && (*i).starts_with(prefix);
+            return (i != files.end() && (*i).starts_with(prefix)) || files.count(file);
         }
 
         return files.count(file);
diff --git a/tests/functional/fetchGitSubmodules.sh b/tests/functional/fetchGitSubmodules.sh
index df81232e5..3ff6697fd 100644
--- a/tests/functional/fetchGitSubmodules.sh
+++ b/tests/functional/fetchGitSubmodules.sh
@@ -40,6 +40,7 @@ initGitRepo $rootRepo
 git -C $rootRepo submodule init
 git -C $rootRepo submodule add $subRepo sub
 git -C $rootRepo add sub
+r0=$(nix eval --impure --raw --expr "(builtins.fetchGit { url = file://$rootRepo; }).outPath")
 git -C $rootRepo commit -m "Add submodule"
 
 rev=$(git -C $rootRepo rev-parse HEAD)
@@ -48,6 +49,7 @@ r1=$(nix eval --raw --expr "(builtins.fetchGit { url = file://$rootRepo; rev = \
 r2=$(nix eval --raw --expr "(builtins.fetchGit { url = file://$rootRepo; rev = \"$rev\"; submodules = false; }).outPath")
 r3=$(nix eval --raw --expr "(builtins.fetchGit { url = file://$rootRepo; rev = \"$rev\"; submodules = true; }).outPath")
 
+[[ $r0 == $r1 ]] # verify that unfetched submodules result in empty directories in dirty mode too
 [[ $r1 == $r2 ]]
 [[ $r2 != $r3 ]]