From a98e52085584d806bd80ab203c7b75c4e361f522 Mon Sep 17 00:00:00 2001
From: Erik Arvstedt <erik.arvstedt@gmail.com>
Date: Fri, 6 Jan 2023 19:44:07 +0100
Subject: [PATCH] build-dotnet-module: avoid `/run/user` for downloading
 packages

Inside `nix-shell`, `TMPDIR` (used by `mktemp`) is set to
`/run/user/<uid>` which is usually a tmpfs stored in RAM.

When fetching a large dotnet deps tree to this tmpdir from a
nix-shell (e.g. via `btcpayserver/update.sh`), this can easily exceed
system RAM and `fetch-deps` fails.

mktemp arg `-t` is deprecated and can be omitted.
---
 pkgs/build-support/dotnet/build-dotnet-module/default.nix | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/pkgs/build-support/dotnet/build-dotnet-module/default.nix b/pkgs/build-support/dotnet/build-dotnet-module/default.nix
index 7f05a3a4eecc..d7d6d68c6c53 100644
--- a/pkgs/build-support/dotnet/build-dotnet-module/default.nix
+++ b/pkgs/build-support/dotnet/build-dotnet-module/default.nix
@@ -190,7 +190,13 @@ stdenvNoCC.mkDerivation (args // {
             esac
         done
 
-        export tmp=$(mktemp -td "${pname}-tmp-XXXXXX")
+        if [[ ''${TMPDIR:-} == /run/user/* ]]; then
+           # /run/user is usually a tmpfs in RAM, which may be too small
+           # to store all downloaded dotnet packages
+           TMPDIR=
+        fi
+
+        export tmp=$(mktemp -d "deps-${pname}-XXXXXX")
         HOME=$tmp/home
 
         exitTrap() {