Handle relative paths and writing nonexistent directories for CONDA_PROJECT_ENVS_PATH

[jkong-anaconda]

Update some behavior around the CONDA_PROJECT_ENVS_PATH variable so that relative paths are always interpreted relative to the project root and non-existent directories are created.

[jkong-anaconda]

@AlbertDeFusco This should handle always making the prefix an absolute path (and you can take a look at the relative path test below, which verifies the prefix).

[AlbertDeFusco]

Could we do it like this?

env_path = self.directory / path

since self.directory is already a Path

[AlbertDeFusco]

actually, i think there might be something missing with relative and absolute handling. For the case

CONDA_PROJECT_ENVS_PATH=/opt/conda/envs:conda_envs:/home/.conda/envs

maybe this is a little extra explicit and there could be a shorter variant

for path in env_paths:
    if not path:
        continue

    ## first setup the Path object
    if path.startswith('/'):
        path = Path(path)
    else:
        # this helps cover an edge case where your project directory is not writable
        # but there may be a writable location elsewhere in the env var
        path = self.directory / path

    if path.exists():
        # the requested path exists, can we write the project envs into it?
        if os.access(path, os.W_OK):
            env_path = path
            break
        else:
            continue
    else:
        # can we create the requsted path and then puth the project envs there?
        if os.access(path.parent, os.W_OK):
            env_path = path
            break
        else:
            continue

envs = OrderedDict()
for env_name, sources in self._project_file.environments.items():
    envs[env_name] = Environment(
        name=env_name,
        sources=tuple([self.directory / str(s) for s in sources]),
        prefix=(env_path / env_name).absolute(),
        lockfile=self.directory / f"conda-lock.{env_name}.yml",
        project=weakref.proxy(self),
    )
Environments = create_model(
    "Environments",
    **{k: (Environment, ...) for k in envs},
    __base__=BaseEnvironments,
)
return Environments(**envs)

[jkong-anaconda]

Updated + added tests to handle the cases where a non-existent path's parent isn't writable, and where the project directory itself is not writable but a path in the environment variable is.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.09%. Comparing base (e4cbec3) to head (323e123).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #161      +/-   ##
==========================================
+ Coverage   97.40%   98.09%   +0.69%     
==========================================
  Files           9        9              
  Lines        1000      996       -4     
==========================================
+ Hits          974      977       +3     
+ Misses         26       19       -7     

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