From f8110737aeedf8ba92ea46a0b1d2d298843d7c06 Mon Sep 17 00:00:00 2001
From: Pol Dellaiera <pol.dellaiera@protonmail.com>
Date: Wed, 18 Dec 2024 18:02:37 +0100
Subject: [PATCH] build-support: add `writableTmpDirAsHomeHook` hook

---
 doc/redirects.json                                |  3 +++
 doc/stdenv/stdenv.chapter.md                      | 11 +++++++++++
 .../setup-hooks/writable-tmpdir-as-home.sh        | 15 +++++++++++++++
 pkgs/top-level/all-packages.nix                   |  7 +++++++
 4 files changed, 36 insertions(+)
 create mode 100644 pkgs/build-support/setup-hooks/writable-tmpdir-as-home.sh

diff --git a/doc/redirects.json b/doc/redirects.json
index 5bf6394e422b..5065007b0ae9 100644
--- a/doc/redirects.json
+++ b/doc/redirects.json
@@ -830,6 +830,9 @@
   "add-bin-to-path.sh": [
     "index.html#add-bin-to-path.sh"
   ],
+  "writable-tmpdir-as-home.sh": [
+    "index.html#writable-tmpdir-as-home.sh"
+  ],
   "bintools-wrapper": [
     "index.html#bintools-wrapper"
   ],
diff --git a/doc/stdenv/stdenv.chapter.md b/doc/stdenv/stdenv.chapter.md
index bc32c7ec404f..d9264b6e7052 100644
--- a/doc/stdenv/stdenv.chapter.md
+++ b/doc/stdenv/stdenv.chapter.md
@@ -1389,6 +1389,17 @@ work as intended in cases with multiple outputs or when binaries are located in
 directories like `sbin/`. These caveats should be considered when using this
 hook, as they might introduce unexpected behavior in some specific cases.
 
+### `writable-tmpdir-as-home.sh` {#writable-tmpdir-as-home.sh}
+
+This setup hook ensures that the directory specified by the `HOME` environment
+variable is writable. If it is not, the hook assigns `HOME` to a writable
+directory (in `.home` in `$NIX_BUILD_TOP`). This adjustment is necessary for
+certain packages that require write access to a home directory. This hook can
+be added to any phase.
+
+By setting `HOME` to a writable directory, this setup hook prevents failures in
+packages that attempt to write to the home directory.
+
 ### Bintools Wrapper and hook {#bintools-wrapper}
 
 The Bintools Wrapper wraps the binary utilities for a bunch of miscellaneous purposes. These are GNU Binutils when targeting Linux, and a mix of cctools and GNU binutils for Darwin. \[The “Bintools” name is supposed to be a compromise between “Binutils” and “cctools” not denoting any specific implementation.\] Specifically, the underlying bintools package, and a C standard library (glibc or Darwin’s libSystem, just for the dynamic loader) are all fed in, and dependency finding, hardening (see below), and purity checks for each are handled by the Bintools Wrapper. Packages typically depend on CC Wrapper, which in turn (at run time) depends on the Bintools Wrapper.
diff --git a/pkgs/build-support/setup-hooks/writable-tmpdir-as-home.sh b/pkgs/build-support/setup-hooks/writable-tmpdir-as-home.sh
new file mode 100644
index 000000000000..f63f3499e736
--- /dev/null
+++ b/pkgs/build-support/setup-hooks/writable-tmpdir-as-home.sh
@@ -0,0 +1,15 @@
+# shellcheck shell=bash
+# This setup hook set the HOME environment variable to a writable directory.
+
+export HOME
+
+writableTmpDirAsHome () {
+    if [ ! -w "$HOME" ]; then
+        HOME="$NIX_BUILD_TOP/.home"
+        mkdir -p "$HOME"
+        export HOME
+    fi
+}
+
+# shellcheck disable=SC2154
+addEnvHooks "$targetOffset" writableTmpDirAsHome
diff --git a/pkgs/top-level/all-packages.nix b/pkgs/top-level/all-packages.nix
index 8e2bd6b78370..a78af701c1ee 100644
--- a/pkgs/top-level/all-packages.nix
+++ b/pkgs/top-level/all-packages.nix
@@ -868,6 +868,13 @@ with pkgs;
     name = "setup-debug-info-dirs-hook";
   } ../build-support/setup-hooks/setup-debug-info-dirs.sh;
 
+  writableTmpDirAsHomeHook = callPackage (
+    { makeSetupHook }:
+    makeSetupHook {
+      name = "writable-tmpdir-as-home-hook";
+    } ../build-support/setup-hooks/writable-tmpdir-as-home.sh
+  ) { };
+
   useOldCXXAbi = makeSetupHook {
     name = "use-old-cxx-abi-hook";
   } ../build-support/setup-hooks/use-old-cxx-abi.sh;