Progress on the installer!

I think it should work for all platforms now using pip, including with
prefixes and staging. Next is to get the installed files locations.

SConstruct

@@ -855,7 +855,7 @@ env['cantera_short_version'] = re.match(r'(\d+\.\d+)', env['cantera_version']).g
 try:
     env["git_commit"] = get_command_output("git", "rev-parse", "--short", "HEAD")
     logger.info(f"Building Cantera from git commit '{env['git_commit']}'")
-except subprocess.CalledProcessError:
+except (subprocess.CalledProcessError, FileNotFoundError):
     env["git_commit"] = "unknown"
 
 # Print values of all build options:
@@ -2066,23 +2066,6 @@ def getParentDirs(path, top=True):
 # Files installed by SCons
 allfiles = FindInstalledFiles()
 
-# Files installed by the Python installer
-if os.path.exists('build/python-installed-files.txt'):
-    with open('build/python-installed-files.txt', 'r') as f:
-        file_list = f.readlines()
-
-    install_base = os.path.dirname(file_list[0].strip())
-    if os.path.exists(install_base):
-        not_listed_files = [s for s in os.listdir(install_base) if not any(s in j for j in file_list)]
-        for f in not_listed_files:
-            f = pjoin(install_base, f)
-            if not os.path.isdir(f) and os.path.exists(f):
-                allfiles.append(File(f))
-    for f in file_list:
-        f = f.strip()
-        if not os.path.isdir(f) and os.path.exists(f):
-            allfiles.append(File(f))
-
 # After removing files (which SCons keeps track of),
 # remove any empty directories (which SCons doesn't track)
 def removeDirectories(target, source, env):
@@ -2108,6 +2091,8 @@ def removeDirectories(target, source, env):
 
 uninstall = env.Command("uninstall", None, Delete(allfiles))
 env.AddPostAction(uninstall, Action(removeDirectories))
+if env["python_package"] == "full":
+    env.AddPostAction(uninstall, Action("$python_cmd_esc -m pip uninstall Cantera"))
 
 ### Windows MSI Installer ###
 if 'msi' in COMMAND_LINE_TARGETS:

interfaces/cython/SConscript

@@ -1,11 +1,15 @@
 """Cython-based Python Module"""
+from __future__ import annotations
+from gettext import install
 import re
-from os.path import join as pjoin
+import os
 from os.path import normpath
 from pathlib import Path
+from threading import local
 from pkg_resources import parse_version
 import json
 from buildutils import *
+from textwrap import dedent
 
 Import('env', 'build', 'install')
 
@@ -32,6 +36,9 @@ testFiles = localenv.RecursiveInstall('cantera/test/data',
                                       '#test/data')
 build(testFiles)
 
+if localenv["python_prefix"]:
+    localenv["python_prefix"] = localenv.subst("$python_prefix")
+
 # Get information needed to build the Python module
 script = """\
 from sysconfig import *
@@ -121,59 +128,59 @@ for f in (multi_glob(localenv, 'cantera', 'py') +
     localenv.Depends(mod, f)
 
 # Determine installation path and install the Python module
-# IMO, if the Python we're installing for is the system Python,
-# the default should be the user site directory.
-python_prefix = "system"
+install_cmd = ["$python_cmd_esc", "-m", "pip", "install"]
+
+
+def get_install_location(user: bool = False, prefix: str = "", root: str = "") -> dict[str, str]:
+    install_script = dedent(f"""
+    from pip import __version__ as pip_version
+    from pkg_resources import parse_version
+    import json
+    pip_version = parse_version(pip_version)
+    if pip_version < parse_version("10.0.0"):
+        from pip.locations import distutils_scheme
+        scheme = distutils_scheme("Cantera", user={user}, root={root or "''"}, prefix={prefix or "''"})
+    else:
+        from pip._internal.locations import get_scheme
+        scheme = get_scheme("Cantera", user={user}, root={root or "''"}, prefix={prefix or "''"})
+
+    if not isinstance(scheme, dict):
+        scheme = {{k: getattr(scheme, k) for k in dir(scheme) if not k.startswith("_")}}
+
+    print(json.dumps(scheme))
+    """)
+    return json.loads(get_command_output(localenv["python_cmd"], "-c", install_script))
+
+
+print(get_install_location())
+
 if localenv['python_prefix'] == 'USER':
     # Install to the OS-dependent user site-packages directory
-    extra = '--user'
-    install_path = Path(get_command_output(localenv["python_cmd"], "-c", "import site; print(site.getuserbase())")).resolve()
+    install_cmd.append("--user")
+    scheme = f"{os.name}_user"
+    install_dir = get_command_output(localenv["python_cmd"], "-c", f"import sysconfig; sysconfig.get_paths({scheme})")
+# If prefix is set which implicitly sets python_prefix,
+# or python_prefix is set explicitly, this path is followed.
 elif localenv['python_prefix']:
-    # A specific location for the Cantera Python module has been given
-    if localenv['debian'] and localenv.subst('${python_prefix}') == '/usr/local':
-        # Installation to /usr/local is the default on Debian-based distributions
-        extra = ''
-    elif localenv['libdirname'] != 'lib':
-        # 64-bit RHEL / Fedora etc. or e.g. x32 Gentoo profile
-        extra = localenv.subst(
-            ' --prefix=${{python_prefix}} --install-scripts=${{python_prefix}}/bin'
-            ' --install-lib=${{python_prefix}}/${{libdirname}}/python{}/site-packages'.format(py_version_short))
-    else:
-        extra = '--user'
-        localenv.AppendENVPath(
-            'PYTHONUSERBASE',
-            normpath(localenv.subst('$python_prefix')))
+    install_cmd.append(f"--prefix={localenv['python_prefix']}")
 else:
-    # Install Python module in the default location
-    extra = ''
+    install_dir = get_command_output(localenv["python_cmd"], "-c", "from sysconfig import get_paths; print(get_paths('posix_prefix')['platlib'])")
 
 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,
-    # which is two directories up from the current working directory of this SConscript
-    # file.
-    stage_absolute = Path.cwd().parents[1].joinpath(env['stage_dir']).resolve()
-    extra += f" --root={stage_absolute}"
+    # path, consider it to be relative to the root of the Cantera source directory.
+    stage_dir = Path(env["stage_dir"])
+    if not stage_dir.is_absolute():
+        stage_dir = Path(Dir("#").abspath) / stage_dir
+
+    install_cmd.append(f"--root={stage_dir.resolve()}")
 
 env['python_module_loc'] = '<unspecified>'
-install_cmd = "$python_cmd_esc -m pip install "
+
+install_cmd.extend(("--no-build-isolation", "--no-deps", "-v", "--force-reinstall", "build/python"))
 if localenv['PYTHON_INSTALLER'] == 'direct':
     mod_inst = install(localenv.Command, 'dummy', mod,
-                       install_cmd + extra +
-                       " --no-build-isolation --no-deps -v --force-reinstall "
-                       "build/python")
-    # this seems suboptimal, but easy_install with its --record option is deprecated and not used
-    # by pip. I need some way to figure out the install directory
-    if "--prefix" in extra:
-        install_path = Path(extra.split("=")[1])
-    elif "--user" in extra:
-        if localenv["python_prefix"]:
-            import os
-            os.environ["PYTHONUSERBASE"] = localenv.subst('$python_prefix')
-        install_path = Path(get_command_output(localenv["python_cmd"], "-c", "import site; print(site.getuserbase())"))
-    if env["stage_dir"]:
-        install_path = stage_absolute / install_path
-    env["python_module_loc"] = str(install_path)
+                       " ".join(install_cmd))
     env['install_python_action'] = mod_inst
 elif localenv['PYTHON_INSTALLER'] == 'debian':
     extra = localenv.subst(' --root=${python_prefix}')