From ef6d134ef8627b9615e5c184b204e411642402a8 Mon Sep 17 00:00:00 2001
From: Ed Morley <501702+edmorley@users.noreply.github.com>
Date: Mon, 16 Dec 2024 15:36:27 +0000
Subject: [PATCH] Stop setting the `LANG` env var

Previously the buildpack would set the `LANG` env var at build
and run time to the value `C.UTF-8`, to match the official Docker
Python images.

However, the env var should not be needed for modern Python,
and so the official Docker Python images no longer set it:
https://github.com/docker-library/python/issues/887
https://github.com/docker-library/python/pull/895

In addition, the older issues typically only affected other distros
such as alpine, or environments where someone had overridden
the system locale, which doesn't apply to the Heroku base images.
---
 CHANGELOG.md         |  4 ++++
 src/layers/python.rs | 11 -----------
 tests/pip_test.rs    |  2 --
 tests/poetry_test.rs |  2 --
 4 files changed, 4 insertions(+), 15 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index ef5f116..511d947 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Removed
+
+- Stopped setting the `LANG` env var. ([#306](https://github.com/heroku/buildpacks-python/pull/306))
+
 ## [0.20.1] - 2024-12-13
 
 ### Fixed
diff --git a/src/layers/python.rs b/src/layers/python.rs
index 785a6c2..81d1587 100644
--- a/src/layers/python.rs
+++ b/src/layers/python.rs
@@ -176,14 +176,6 @@ fn generate_layer_env(layer_path: &Path, python_version: &PythonVersion) -> Laye
             )),
         )
         .chainable_insert(Scope::Build, ModificationBehavior::Delimiter, "CPATH", ":")
-        // Ensure Python uses a Unicode locale, to prevent the issues described in:
-        // https://github.com/docker-library/python/pull/570
-        .chainable_insert(
-            Scope::All,
-            ModificationBehavior::Override,
-            "LANG",
-            "C.UTF-8",
-        )
         // We have to set `PKG_CONFIG_PATH` explicitly, since the automatic path set by lifecycle/libcnb
         // is `<layer>/pkgconfig/`, whereas Python's pkgconfig files are at `<layer>/lib/pkgconfig/`.
         .chainable_insert(
@@ -330,7 +322,6 @@ mod tests {
     fn python_layer_env() {
         let mut base_env = Env::new();
         base_env.insert("CPATH", "/base");
-        base_env.insert("LANG", "this-should-be-overridden");
         base_env.insert("PKG_CONFIG_PATH", "/base");
         base_env.insert("PYTHONHOME", "this-should-be-overridden");
         base_env.insert("PYTHONUNBUFFERED", "this-should-be-overridden");
@@ -341,7 +332,6 @@ mod tests {
             utils::environment_as_sorted_vector(&layer_env.apply(Scope::Build, &base_env)),
             [
                 ("CPATH", "/layer-dir/include/python3.11:/base"),
-                ("LANG", "C.UTF-8"),
                 ("PKG_CONFIG_PATH", "/layer-dir/lib/pkgconfig:/base"),
                 ("PYTHONHOME", "/layer-dir"),
                 ("PYTHONUNBUFFERED", "1"),
@@ -352,7 +342,6 @@ mod tests {
             utils::environment_as_sorted_vector(&layer_env.apply(Scope::Launch, &base_env)),
             [
                 ("CPATH", "/base"),
-                ("LANG", "C.UTF-8"),
                 ("PKG_CONFIG_PATH", "/base"),
                 ("PYTHONHOME", "/layer-dir"),
                 ("PYTHONUNBUFFERED", "1"),
diff --git a/tests/pip_test.rs b/tests/pip_test.rs
index 0feea07..5f8b712 100644
--- a/tests/pip_test.rs
+++ b/tests/pip_test.rs
@@ -40,7 +40,6 @@ fn pip_basic_install_and_cache_reuse() {
                 
                 ## Testing buildpack ##
                 CPATH=/layers/heroku_python/venv/include:/layers/heroku_python/python/include/python3.13:/layers/heroku_python/python/include
-                LANG=C.UTF-8
                 LD_LIBRARY_PATH=/layers/heroku_python/venv/lib:/layers/heroku_python/python/lib:/layers/heroku_python/pip/lib
                 LIBRARY_PATH=/layers/heroku_python/venv/lib:/layers/heroku_python/python/lib:/layers/heroku_python/pip/lib
                 PATH=/layers/heroku_python/venv/bin:/layers/heroku_python/python/bin:/layers/heroku_python/pip/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
@@ -84,7 +83,6 @@ fn pip_basic_install_and_cache_reuse() {
         assert_eq!(
             command_output.stdout,
             formatdoc! {"
-                LANG=C.UTF-8
                 LD_LIBRARY_PATH=/layers/heroku_python/venv/lib:/layers/heroku_python/python/lib
                 PATH=/layers/heroku_python/venv/bin:/layers/heroku_python/python/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
                 PIP_PYTHON=/layers/heroku_python/venv
diff --git a/tests/poetry_test.rs b/tests/poetry_test.rs
index 81b7a4d..05887af 100644
--- a/tests/poetry_test.rs
+++ b/tests/poetry_test.rs
@@ -38,7 +38,6 @@ fn poetry_basic_install_and_cache_reuse() {
                 
                 ## Testing buildpack ##
                 CPATH=/layers/heroku_python/venv/include:/layers/heroku_python/python/include/python3.13:/layers/heroku_python/python/include
-                LANG=C.UTF-8
                 LD_LIBRARY_PATH=/layers/heroku_python/venv/lib:/layers/heroku_python/python/lib:/layers/heroku_python/poetry/lib
                 LIBRARY_PATH=/layers/heroku_python/venv/lib:/layers/heroku_python/python/lib:/layers/heroku_python/poetry/lib
                 PATH=/layers/heroku_python/venv/bin:/layers/heroku_python/python/bin:/layers/heroku_python/poetry/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
@@ -77,7 +76,6 @@ fn poetry_basic_install_and_cache_reuse() {
         assert_eq!(
             command_output.stdout,
             formatdoc! {"
-                LANG=C.UTF-8
                 LD_LIBRARY_PATH=/layers/heroku_python/venv/lib:/layers/heroku_python/python/lib
                 PATH=/layers/heroku_python/venv/bin:/layers/heroku_python/python/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
                 PYTHONHOME=/layers/heroku_python/python