`path:` version does not work reliably (asdf v0.16)

[jacktose]

Provide environment information

OS:
Linux ad-user-ads-11.s.xx.xxx 3.10.0-1160.90.1.el7.x86_64 #1 SMP Thu May 4 15:21:22 UTC 2023 x86_64 x86_64 x86_64 GNU/Linux

SHELL:
GNU bash, version 5.2.37(1)-release (x86_64-pc-linux-gnu)
Copyright (C) 2022 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>

This is free software; you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

BASH VERSION:
5.2.37(1)-release

ASDF VERSION:
0.16.7

ASDF INTERNAL VARIABLES:
ASDF_DEFAULT_TOOL_VERSIONS_FILENAME=.tool-versions
ASDF_DATA_DIR=/usr/lusers/jacktose/.asdf
ASDF_CONFIG_FILE=/usr/lusers/jacktose/.asdfrc

ASDF INSTALLED PLUGINS:
python    https://github.com/danhper/asdf-python.git 5e277e24ec2b6739728f458c1c25eeb2a8b8bb79

To Reproduce

1. Have a non-asdf python installation:

   $ /netops/local/python-3.9.2/bin/python3.9 -V
   Python 3.9.2
   

2. Configure asdf to use it, with path: syntax:

   $ asdf set python path:/netops/local/python-3.9.2
   $ cat .tool-versions
   python path:/netops/local/python-3.9.2
   $ asdf current python
   Name            Version                         Source                                      Installed
   python          path:/netops/local/python-3.9.2 /usr/lusers/jacktose/code/l2/.tool-versions true
   

3. Check which python is used:

   $ asdf which python
   No python executable found for python path:/netops/local/python-3.9.2
   $ python -V
   No executable python found for current version. Please select a different version or install python manually for the current version
   

4. Compare to python3:

   $ asdf which python3
   /netops/local/python-3.9.2/bin/python3
   $ python3 -V
   Python 3.9.2
   

5. Try path: with asdf-installed fallback version:

   $ asdf set python path:/netops/local/python-3.9.2 3.9.15
   $ asdf current python
   Name            Version                                Source                                      Installed
   python          path:/netops/local/python-3.9.2 3.9.15 /usr/lusers/jacktose/code/l2/.tool-versions true
   
   $ asdf which python
   /usr/lusers/jacktose/.asdf/installs/python/3.9.15/bin/python
   $ python -V
   Python 3.9.15
   
   $ asdf which python3
   /usr/lusers/jacktose/.asdf/installs/python/3.9.15/bin/python3
   $ python3 -V
   Python 3.9.15
   

Note that shims are fine:

$ which python
~/.asdf/shims/python
$ which python3
~/.asdf/shims/python3

And both shims work as expected for asdf-installed python:

$ asdf set python 3.9.15
$ asdf current python
Name            Version         Source                                      Installed
python          3.9.15          /usr/lusers/jacktose/code/l2/.tool-versions true

$ asdf which python
/usr/lusers/jacktose/.asdf/installs/python/3.9.15/bin/python
$ python -V
Python 3.9.15

$ asdf which python3
/usr/lusers/jacktose/.asdf/installs/python/3.9.15/bin/python3
$ python3 -V
Python 3.9.15

Describe the Bug

path: version is ignored, unless it is the only version listed and you use the python3 shim.

asdf set python ...	expected	python -V	python3 -V
3.9.15	3.9.15	3.9.15 ✅	3.9.15 ✅
path:/netops/local/python-3.9.2	3.9.2	error ❌	3.9.2 ✅
path:/netops/local/python-3.9.2 3.9.15	3.9.2	3.9.15 ❌	3.9.15 ❌

Expected Behaviour

path: versions (assuming there's a valid python there) should work with both python & python3 shims, and follow normal precedence rules. See “expected” column above.

[jacktose]

Note that #206 is a similar (but subtly different) problem in asdf <0.16.