From d8032fbecf0f2e4f9bf88993bc434b66076f2c57 Mon Sep 17 00:00:00 2001
From: Ed Morley <501702+edmorley@users.noreply.github.com>
Date: Tue, 17 Dec 2024 15:15:57 +0000
Subject: [PATCH] Stop setting the `PYTHONHOME` env var

Since it was only set to work around a uWSGI bug, and that
bug does not occur when using a venv (which we now use
as of #257).

Closes #265.
GUS-W-17454520.
---
 CHANGELOG.md         |  1 +
 src/layers/python.rs | 17 -----------------
 tests/pip_test.rs    |  2 --
 tests/poetry_test.rs |  2 --
 4 files changed, 1 insertion(+), 21 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 6565704..13f34cd 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -15,6 +15,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Removed
 
 - Stopped setting the `LANG` env var. ([#306](https://github.com/heroku/buildpacks-python/pull/306))
+- Stopped setting the `PYTHONHOME` env var. ([#309](https://github.com/heroku/buildpacks-python/pull/309))
 
 ## [0.20.1] - 2024-12-13
 
diff --git a/src/layers/python.rs b/src/layers/python.rs
index 81d1587..fbd1c29 100644
--- a/src/layers/python.rs
+++ b/src/layers/python.rs
@@ -190,20 +190,6 @@ fn generate_layer_env(layer_path: &Path, python_version: &PythonVersion) -> Laye
             "PKG_CONFIG_PATH",
             ":",
         )
-        // We relocate Python (install into a different location to which it was compiled), which
-        // Python handles fine since it recalculates its actual location at startup. However, the
-        // uWSGI package uses the wrong `sysconfig` APIs so tries to reference the old compile
-        // location, unless we override that by setting `PYTHONHOME`. See:
-        // https://docs.python.org/3/library/sys_path_init.html
-        // https://github.com/unbit/uwsgi/issues/2525
-        // In addition, some legacy apps have `PYTHONHOME` set to an invalid value, so if we did not
-        // set it explicitly here, they would fail to run both during the build and at run-time.
-        .chainable_insert(
-            Scope::All,
-            ModificationBehavior::Override,
-            "PYTHONHOME",
-            layer_path,
-        )
         // Disable Python's output buffering to ensure logs aren't dropped if an app crashes.
         .chainable_insert(
             Scope::All,
@@ -323,7 +309,6 @@ mod tests {
         let mut base_env = Env::new();
         base_env.insert("CPATH", "/base");
         base_env.insert("PKG_CONFIG_PATH", "/base");
-        base_env.insert("PYTHONHOME", "this-should-be-overridden");
         base_env.insert("PYTHONUNBUFFERED", "this-should-be-overridden");
 
         let layer_env = generate_layer_env(Path::new("/layer-dir"), &PythonVersion::new(3, 11, 1));
@@ -333,7 +318,6 @@ mod tests {
             [
                 ("CPATH", "/layer-dir/include/python3.11:/base"),
                 ("PKG_CONFIG_PATH", "/layer-dir/lib/pkgconfig:/base"),
-                ("PYTHONHOME", "/layer-dir"),
                 ("PYTHONUNBUFFERED", "1"),
                 ("SOURCE_DATE_EPOCH", "315532801"),
             ]
@@ -343,7 +327,6 @@ mod tests {
             [
                 ("CPATH", "/base"),
                 ("PKG_CONFIG_PATH", "/base"),
-                ("PYTHONHOME", "/layer-dir"),
                 ("PYTHONUNBUFFERED", "1"),
             ]
         );
diff --git a/tests/pip_test.rs b/tests/pip_test.rs
index 00e5dc0..40d0b02 100644
--- a/tests/pip_test.rs
+++ b/tests/pip_test.rs
@@ -47,7 +47,6 @@ fn pip_basic_install_and_cache_reuse() {
                 PIP_DISABLE_PIP_VERSION_CHECK=1
                 PIP_PYTHON=/layers/heroku_python/venv
                 PKG_CONFIG_PATH=/layers/heroku_python/python/lib/pkgconfig
-                PYTHONHOME=/layers/heroku_python/python
                 PYTHONUNBUFFERED=1
                 PYTHONUSERBASE=/layers/heroku_python/pip
                 SOURCE_DATE_EPOCH=315532801
@@ -85,7 +84,6 @@ fn pip_basic_install_and_cache_reuse() {
             formatdoc! {"
                 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
                 PYTHONUNBUFFERED=1
                 VIRTUAL_ENV=/layers/heroku_python/venv
             "}
diff --git a/tests/poetry_test.rs b/tests/poetry_test.rs
index 05887af..d822b39 100644
--- a/tests/poetry_test.rs
+++ b/tests/poetry_test.rs
@@ -42,7 +42,6 @@ fn poetry_basic_install_and_cache_reuse() {
                 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
                 PKG_CONFIG_PATH=/layers/heroku_python/python/lib/pkgconfig
-                PYTHONHOME=/layers/heroku_python/python
                 PYTHONUNBUFFERED=1
                 PYTHONUSERBASE=/layers/heroku_python/poetry
                 SOURCE_DATE_EPOCH=315532801
@@ -78,7 +77,6 @@ fn poetry_basic_install_and_cache_reuse() {
             formatdoc! {"
                 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
                 PYTHONUNBUFFERED=1
                 VIRTUAL_ENV=/layers/heroku_python/venv
             "}