Fix python-minimal installation issues

README.rst

@@ -89,7 +89,7 @@ possible.
 Development Site
 ================
 
-The current development version is 2.6.0b1. The current stable version is
+The current development version is 2.6.0b2. The current stable version is
 2.5.1. The `latest Cantera source code <https://github.com/Cantera/cantera>`_,
 the `issue tracker <https://github.com/Cantera/cantera/issues>`_ for bugs and
 enhancement requests, `downloads of Cantera releases and binary installers

SConstruct

@@ -872,7 +872,7 @@ for arg in ARGUMENTS:
         logger.error(f"Encountered unexpected command line option: '{arg}'")
         sys.exit(1)
 
-env["cantera_version"] = "2.6.0b1"
+env["cantera_version"] = "2.6.0b2"
 # For use where pre-release tags are not permitted (MSI, sonames)
 env['cantera_pure_version'] = re.match(r'(\d+\.\d+\.\d+)', env['cantera_version']).group(0)
 env['cantera_short_version'] = re.match(r'(\d+\.\d+)', env['cantera_version']).group(0)

doc/doxygen/Doxyfile

@@ -38,7 +38,7 @@ PROJECT_NAME           = Cantera
 # could be handy for archiving the generated documentation or if some version
 # control system is used.
 
-PROJECT_NUMBER         = 2.6.0b1
+PROJECT_NUMBER         = 2.6.0b2
 
 # Using the PROJECT_BRIEF tag one can provide an optional one line description
 # for a project that appears at the top of each page and should give viewer a

interfaces/cython/cantera/ck2yaml.py

@@ -1902,7 +1902,7 @@ def write_yaml(self, name='gas', out_name='mech.yaml'):
             metadata = BlockMap([
                 ("generator", "ck2yaml"),
                 ("input-files", FlowList(files)),
-                ("cantera-version", "2.6.0b1"),
+                ("cantera-version", "2.6.0b2"),
                 ("date", formatdate(localtime=True)),
             ])
             if desc.strip():

interfaces/cython/cantera/cti2yaml.py

@@ -1661,7 +1661,7 @@ def convert(filename=None, output_name=None, text=None, encoding="latin-1"):
         # information regarding conversion
         metadata = BlockMap([
             ("generator", "cti2yaml"),
-            ("cantera-version", "2.6.0b1"),
+            ("cantera-version", "2.6.0b2"),
             ("date", formatdate(localtime=True)),
         ])
         if filename != "<string>":

interfaces/cython/cantera/ctml2yaml.py

@@ -2641,7 +2641,7 @@ def convert(
     metadata = BlockMap(
         {
             "generator": "ctml2yaml",
-            "cantera-version": "2.6.0b1",
+            "cantera-version": "2.6.0b2",
             "date": formatdate(localtime=True),
         }
     )

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')
 
@@ -32,17 +34,56 @@ localenv.Depends(mod, [make_setup, readme, license, "setup.py", "pyproject.toml"
 install_cmd = ["$python_cmd_esc", "-m", "pip", "install"]
 user_install = False
 python_prefix = None
-python_root = None
 if localenv["PYTHON_INSTALLER"] == "direct":
     if localenv["python_prefix"] == "USER":
         # Install to the OS-dependent user site-packages directory
         install_cmd.append("--user")
         user_install = True
     elif localenv["python_prefix"]:
         # A specific location for the Cantera python module has been given
-        install_cmd.extend((f"--prefix={localenv.subst('python_prefix')}",
+        install_cmd.extend((f"--prefix={localenv.subst('$python_prefix')}",
                             "--no-warn-script-location"))
-        python_prefix = localenv.subst("python_prefix")
+        python_prefix = localenv.subst("$python_prefix")
+    elif not env["default_prefix"]:
+        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