Add an implicit-pkg-path-as-logger-name test

A bit of test driven dev to anticipate support  of `.log.get_logger()`
usage such that it can be called from arbitrary sub-modules, themselves
embedded in arbitrary sub-pkgs, of some project; the when not provided,
the `sub_name` passed to the `Logger.getChild(<sub_name>)` will be set
as the sub-pkg path "down to" the calling module.

IOW if you call something like,

`log = tractor.log.get_logger(pkg_name='mypylib')`

from some `submod.py` in a project-dir that looks like,

mypylib/
  mod.py
  subpkg/
    submod.py  <- calling module

the `log: StackLevelAdapter` child-`Logger` instance will have a
`.name: str = 'mypylib.subpkg'`, discluding the `submod` part since this
already rendered as the `{filename}` header in `log.LOG_FORMAT`.

Previously similar behaviour would be obtained by passing
`get_logger(name=__name__)` in the calling module and so much so it
motivated me to make this the default, presuming we can introspect for
the info.

Impl deats,
- duplicated a `load_module_from_path()` from `modden` to load the
  `testdir` rendered py project dir from its path.
 |_should prolly factor it down to this lib anyway bc we're going to
   need it for hot code reload? (well that and `watchfiles` Bp)
- in each of `mod.py` and `submod.py` render the `get_logger()` code
  sin `name`, expecting the (coming shortly) implicit introspection
  feat to do this.
- do `.name` and `.parent` checks against expected sub-logger values
  from `StackLevelAdapter.logger.getChildren()`.

tests/test_log_sys.py

@@ -2,16 +2,29 @@
 `tractor.log`-wrapping unit tests.
 
 '''
+import importlib
+from pathlib import Path
+import shutil
+import sys
+from types import ModuleType
+
+import pytest
 import tractor
 
 
-def test_root_pkg_not_duplicated():
+def test_root_pkg_not_duplicated_in_logger_name():
+    '''
+    When both `_root_name` and `name` are passed and they have
+    a common `<root_name>.< >` prefix, ensure that it is not
+    duplicated in the child's `StackLevelAdapter.name: str`.
 
+    '''
     project_name: str = 'pylib'
     pkg_path: str = 'pylib.subpkg.mod'
 
-    log = tractor.log.get_logger(
+    proj_log = tractor.log.get_logger(
         _root_name=project_name,
+        mk_sublog=False,
     )
 
     sublog = tractor.log.get_logger(
@@ -19,11 +32,111 @@ def test_root_pkg_not_duplicated():
         name=pkg_path,
     )
 
-    assert log is not sublog
-    assert sublog.name.count(log.name) == 1
+    assert proj_log is not sublog
+    assert sublog.name.count(proj_log.name) == 1
     assert 'mod' not in sublog.name
 
 
+# ?TODO, move this into internal libs?
+# -[ ] we already use it in `modden.config._pymod` as well
+def load_module_from_path(
+    path: Path,
+    module_name: str|None = None,
+) -> ModuleType:
+    '''
+    Taken from SO,
+    https://stackoverflow.com/a/67208147
+
+    which is based on stdlib docs,
+    https://docs.python.org/3/library/importlib.html#importing-a-source-file-directly
+
+    '''
+    module_name = module_name or path.stem
+    spec = importlib.util.spec_from_file_location(
+        module_name,
+        str(path),
+    )
+    module = importlib.util.module_from_spec(spec)
+    sys.modules[module_name] = module
+    spec.loader.exec_module(module)
+    return module
+
+
+def test_implicit_mod_name_applied_for_child(
+    testdir: pytest.Pytester,
+):
+    '''
+    Verify that when `.log.get_logger(pkg_name='pylib')` is called
+    from a given sub-mod from within the `pylib` pkg-path, we
+    implicitly set the equiv of `name=__name__` from the caller's
+    module.
+
+    '''
+    proj_name: str = 'snakelib'
+    mod_code: str = (
+        f'import tractor\n'
+        f'\n'
+        f'log = tractor.log.get_logger(_root_name="{proj_name}")\n'
+    )
+
+    # create a sub-module for each pkg layer
+    _lib = testdir.mkpydir(proj_name)
+    pkg: Path = Path(_lib)
+    subpkg: Path = pkg / 'subpkg'
+    subpkg.mkdir()
+
+    pkgmod: Path = subpkg / "__init__.py"
+    pkgmod.touch()
+
+    _submod: Path = testdir.makepyfile(
+        _mod=mod_code,
+    )
+
+    pkg_mod = pkg / 'mod.py'
+    pkg_subpkg_submod = subpkg / 'submod.py'
+    shutil.copyfile(
+        _submod,
+        pkg_mod,
+    )
+    shutil.copyfile(
+        _submod,
+        pkg_subpkg_submod,
+    )
+    testdir.chdir()
+
+    # XXX NOTE, once the "top level" pkg mod has been
+    # imported, we can then use `import` syntax to
+    # import it's sub-pkgs and modules.
+    pkgmod = load_module_from_path(
+        Path(pkg / '__init__.py'),
+        module_name=proj_name,
+    )
+    pkg_root_log = tractor.log.get_logger(
+        _root_name=proj_name,
+        mk_sublog=False,
+    )
+    assert pkg_root_log.name == proj_name
+    assert not pkg_root_log.logger.getChildren()
+
+    from snakelib import mod
+    assert mod.log.name == proj_name
+
+    from snakelib.subpkg import submod
+    assert (
+        submod.log.name
+        ==
+        submod.__package__  # ?TODO, use this in `.get_logger()` instead?
+        ==
+        f'{proj_name}.subpkg'
+    )
+
+    sub_logs = pkg_root_log.logger.getChildren()
+    assert len(sub_logs) == 1  # only one nested sub-pkg module
+    assert submod.log.logger in sub_logs
+
+    # breakpoint()
+
+
 # TODO, moar tests against existing feats:
 # ------ - ------
 # - [ ] color settings?