From 183939da54831b11f389d9863a0e5b41aaf1ddc5 Mon Sep 17 00:00:00 2001
From: Jeff Huffman <tejing@tejing.com>
Date: Sat, 21 Jan 2023 05:33:20 -0500
Subject: [PATCH] improve error when srcs is used with directories with the
 same post-hash name

---
 pkgs/stdenv/generic/setup.sh | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/pkgs/stdenv/generic/setup.sh b/pkgs/stdenv/generic/setup.sh
index b1b982ecdffc..cbf2a2ceb8de 100644
--- a/pkgs/stdenv/generic/setup.sh
+++ b/pkgs/stdenv/generic/setup.sh
@@ -992,13 +992,22 @@ stripHash() {
 unpackCmdHooks+=(_defaultUnpack)
 _defaultUnpack() {
     local fn="$1"
+    local destination
 
     if [ -d "$fn" ]; then
 
+        destination="$(stripHash "$fn")"
+
+        if [ -e "$destination" ]; then
+            echo "Cannot copy $fn to $destination: destination already exists!"
+            echo "Did you specify two \"srcs\" with the same \"name\"?"
+            return 1
+        fi
+
         # We can't preserve hardlinks because they may have been
         # introduced by store optimization, which might break things
         # in the build.
-        cp -pr --reflink=auto -- "$fn" "$(stripHash "$fn")"
+        cp -pr --reflink=auto -- "$fn" "$destination"
 
     else