Fix `pytest` config-dir isolation in subactors

The old (commented-out) `get_app_dir()` override gated on
`'pytest' in sys.modules` which can NEVER work in spawned
subactors (fresh procs, no pytest import); as a result test
`paperboi`/daemon actors were writing into the user's REAL
`~/.config/piker/accounting/` files.. friggin yikes.

Deats,
- add `config._maybe_use_test_dir()` which lazily (at
  conf-path access time, NOT import time) reads the
  `piker_test_dir` entry from
  `tractor.runtime._state._runtime_vars['piker_vars']` as
  pre-loaded by `open_piker_runtime()` from the
  `tests.conftest._open_test_pikerd()` overrides.
- hook it in `get_conf_dir()` and route `get_conf_path()`
  + `load()`'s mkdir through `get_conf_dir()`.
- route `.accounting._ledger` / `._pos` dir derivation
  through `config.get_conf_dir()` (was reading the
  `_config_dir` global directly, bypassing the override);
  also `mkdir(parents=True, exist_ok=True)` for nested
  tmp-dir creation.

(this patch was generated in some part by [`claude-code`][claude-code-gh])
[claude-code-gh]: https://github.com/anthropics/claude-code

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

piker/accounting/_ledger.py

@@ -324,10 +324,13 @@ def load_ledger(
     ldir: Path = (
         dirpath
         or
-        config._config_dir / 'accounting' / 'ledgers'
+        config.get_conf_dir() / 'accounting' / 'ledgers'
     )
     if not ldir.is_dir():
-        ldir.mkdir()
+        ldir.mkdir(
+            parents=True,
+            exist_ok=True,
+        )
 
     fname = f'trades_{brokername}_{acctid}.toml'
     fpath: Path = ldir / fname

piker/accounting/_pos.py

@@ -785,9 +785,16 @@ def load_account(
     legacy_fn: str = f'pps.{brokername}.{acctid}.toml'
     fn: str = f'account.{brokername}.{acctid}.toml'
 
-    dirpath: Path = dirpath or (config._config_dir / 'accounting')
+    dirpath: Path = (
+        dirpath
+        or
+        (config.get_conf_dir() / 'accounting')
+    )
     if not dirpath.is_dir():
-        dirpath.mkdir()
+        dirpath.mkdir(
+            parents=True,
+            exist_ok=True,
+        )
 
     conf, path = config.load(
         path=dirpath / fn,

piker/config.py

@@ -188,6 +188,48 @@ def _override_config_dir(
     _config_dir = path
 
 
+def _maybe_use_test_dir() -> None:
+    '''
+    When running under the `pytest` harness, override
+    the config dir to the per-test-tmp dir "passed down"
+    the actor tree via `tractor`'s runtime-vars
+    inheritance mechanism.
+
+    See the `tractor_runtime_overrides` usage in our
+    `tests.conftest._open_test_pikerd()` as well as
+    `.service._actor_runtime.open_piker_runtime()` for
+    the root-actor's pre-loading of the var state.
+
+    NOTE: this must be checked lazily at config-path
+    access time (NOT import time) since sub-actors only
+    receive runtime-vars once their `tractor` runtime
+    has fully booted.
+
+    '''
+    global _config_dir
+    import tractor
+    actor = tractor.current_actor(
+        err_on_no_runtime=False,
+    )
+    if actor is None:
+        return
+
+    rvs: dict = tractor.runtime._state._runtime_vars
+    pvars: dict|None = rvs.get('piker_vars')
+    if (
+        pvars
+        and
+        (testdir := pvars.get('piker_test_dir'))
+    ):
+        testdirpath = Path(testdir)
+        assert testdirpath.exists(), (
+            f'piker test harness might be borked!?\n'
+            f'testdirpath: {testdirpath!r}\n'
+        )
+        if _config_dir != testdirpath:
+            _override_config_dir(testdirpath)
+
+
 def _conf_fn_w_ext(
     name: str,
 ) -> str:
@@ -201,6 +243,7 @@ def get_conf_dir() -> Path:
     on the local filesystem.
 
     '''
+    _maybe_use_test_dir()
     return _config_dir
 
 
@@ -226,7 +269,7 @@ def get_conf_path(
         assert str(conf_name) in _conf_names
 
     fn = _conf_fn_w_ext(conf_name)
-    return _config_dir / Path(fn)
+    return get_conf_dir() / Path(fn)
 
 
 def repodir() -> Path:
@@ -271,8 +314,9 @@ def load(
 
     '''
     # create the $HOME/.config/piker dir if dne
-    if not _config_dir.is_dir():
+    conf_dir: Path = get_conf_dir()
-        _config_dir.mkdir(
+    if not conf_dir.is_dir():
+        conf_dir.mkdir(
             parents=True,
             exist_ok=True,
         )