Combined packages (multi packages) fail on windows

[cfxegbert]

A simple combined package combined_test.py

name = "combined_test"
versions = ["1.0"]

def commands():
    info("testing")

On a non-windows environment

> rez-env combined_test                                                                                                                                                                                                                                                                                          
testing

You are now in a rez-configured environment.

resolved by rminsk@LMR007X6202HOME, on Fri May 17 11:40:56 2024, using Rez v3.1.0

requested packages:
combined_test
~platform==osx  (implicit)
~arch==arm64    (implicit)
~os==osx-13     (implicit)

resolved packages:
combined_test-1.0  /Users/rminsk/packages/combined_test.py<1.0>[]  (local)

> env | grep REZ_COMBINED_TEST | sort                                                                                                                                                                                                                                                                            
REZ_COMBINED_TEST_BASE=None
REZ_COMBINED_TEST_MAJOR_VERSION=1
REZ_COMBINED_TEST_MINOR_VERSION=0
REZ_COMBINED_TEST_PATCH_VERSION=
REZ_COMBINED_TEST_ROOT=None
REZ_COMBINED_TEST_VERSION=1.0

Notice that the base and root are set to None on a combined package.

On a windows environment:

$ rez-env combined_test
Traceback (most recent call last):
  File "C:\Program Files\Python310\lib\runpy.py", line 196, in _run_module_as_main
    return _run_code(code, main_globals, None,
  File "C:\Program Files\Python310\lib\runpy.py", line 86, in _run_code
    exec(code, run_globals)
  File "C:\Users\1minsr002\rez\Scripts\rez\rez-env.exe\__main__.py", line 7, in <module>
  File "c:\users\1minsr002\rez\lib\site-packages\rez\cli\_entry_points.py", line 148, in run_rez_env
    return run("env")
  File "c:\users\1minsr002\rez\lib\site-packages\rez\cli\_main.py", line 189, in run
    returncode = run_cmd()
  File "c:\users\1minsr002\rez\lib\site-packages\rez\cli\_main.py", line 181, in run_cmd
    return func(opts, opts.parser, extra_arg_groups)
  File "c:\users\1minsr002\rez\lib\site-packages\rez\cli\env.py", line 253, in command
    returncode, _, _ = context.execute_shell(
  File "c:\users\1minsr002\rez\lib\site-packages\rez\resolved_context.py", line 1045, in _check
    return fn(self, *nargs, **kwargs)
  File "c:\users\1minsr002\rez\lib\site-packages\rez\resolved_context.py", line 1437, in execute_shell
    self._execute(executor)
  File "c:\users\1minsr002\rez\lib\site-packages\rez\utils\memcached.py", line 262, in wrapper
    return func(*nargs, **kwargs)
  File "c:\users\1minsr002\rez\lib\site-packages\rez\resolved_context.py", line 2060, in _execute
    executor.setenv(prefix + "_BASE", normalized(pkg.base))
  File "c:\users\1minsr002\rez\lib\site-packages\rez\resolved_context.py", line 1961, in normalized
    return executor.normalize_path(path)
  File "c:\users\1minsr002\rez\lib\site-packages\rez\rex.py", line 1349, in normalize_path
    return self.interpreter.normalize_path(path)
  File "c:\users\1minsr002\rez\lib\site-packages\rezplugins\shell\_utils\powershell_base.py", line 252, in normalize_path
    return to_windows_path(path)
  File "c:\users\1minsr002\rez\lib\site-packages\rezplugins\shell\_utils\windows.py", line 47, in to_windows_path
    return path.replace('/', '\\')
AttributeError: 'NoneType' object has no attribute 'replace'

This is coming from setting the _BASE and _ROOT environment variables
https://github.com/AcademySoftwareFoundation/rez/blob/main/src/rez/resolved_context.py#L2060-L2070
The normalize function on non-windows environments just returns the passed in variable. On windows it tries to convert drive letters to mount points (gitbash) and "/" to "\" (gitbash and powershell) assuming the value passed in is a string. On non-windows environments the None value is converted to string in setenv when the value is eventually passed to ActionManager._format where if the value is not a str or EscapedString it is converted to string.
https://github.com/AcademySoftwareFoundation/rez/blob/main/src/rez/rex.py#L233-L238

I have thought of three different solutions:

1. Change the the normalized function to do a None check and return the string "None." This would be backwards compatible with the current non-windows behavior.
2. If pkg.base/pkg.root is None then set the environment variable to the empty string. This would set an empty environment on non-windows environment and unset the environment variable on windows environments. This seems the least desirable because of the different behavior between windows and non-windows.
3. If pkg.base/pkg.root is None then do not set the _BASE and _ROOT environment variables. This consistent across platforms but is a change of behavior for non-windows environments.

I have implemented solution 1 and will be submitting a pull request shortly.

Environment

• OS Windows
• Rez version 3.1.1
• Rez python version 3.10.10

[maxnbk]

assigning myself to remind myself to dig into the origins and intent of this feature