From da3985aceb02b6cf42b88a5d4913f70fc0aff101 Mon Sep 17 00:00:00 2001
From: Ray Speth <speth@mit.edu>
Date: Sun, 10 Apr 2022 11:15:10 -0400
Subject: [PATCH] [SCons] Prevent aggressive pip uninstallation of
 cantera-minimal

Fixes #1230
---
 interfaces/python_minimal/SConscript | 39 ++++++++++++++++++++++++++++
 1 file changed, 39 insertions(+)

diff --git a/interfaces/python_minimal/SConscript b/interfaces/python_minimal/SConscript
index 1ae8a19370..3a2a5fd353 100644
--- a/interfaces/python_minimal/SConscript
+++ b/interfaces/python_minimal/SConscript
@@ -1,6 +1,8 @@
 """Minimal Python Module"""
 from pathlib import Path
 from buildutils import *
+import json
+import re
 
 Import('env', 'build', 'install')
 
@@ -46,6 +48,43 @@ if localenv["PYTHON_INSTALLER"] == "direct":
         install_cmd.append(f"--prefix={env['prefix']}")
         python_prefix = env["prefix"]
 
+# Get information about installation paths
+script = """\
+import json
+import site
+vars = {
+    "site_packages": site.getsitepackages(),
+    "user_site_packages": site.getusersitepackages(),
+}
+print(json.dumps(vars))
+"""
+info = json.loads(get_command_output(localenv["python_cmd"], "-c", script))
+site_packages = info["site_packages"]
+user_site_packages = info["user_site_packages"]
+
+# Check for existing Python module installation. Allow pip to remove an existing
+# installation only if we're installing to the same location. Also disable
+# uninstallation if we're installing to a staging directory.
+if env["stage_dir"]:
+    install_cmd.append("--ignore-installed")
+else:
+    info = get_command_output(
+        localenv["python_cmd"], "-m", "pip", "show", "cantera-minimal",
+        ignore_errors=True
+    )
+
+    if user_install:
+        test_prefix = Path(user_site_packages).parents[2]
+    elif python_prefix is None:
+        test_prefix = Path(site_packages[0]).parents[2]
+    else:
+        test_prefix = Path(python_prefix)
+
+    match = re.search(r"Location: (.*)\n", info, re.MULTILINE)
+    existing_prefix = Path(match.group(1)).parents[2] if match else None
+    if existing_prefix and existing_prefix != test_prefix:
+        install_cmd.append("--ignore-installed")
+
 if env["stage_dir"]:
     # Get the absolute path to the stage directory. If the stage directory is a relative
     # path, consider it to be relative to the root of the Cantera source directory.