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fix: use _unsloth_stub sentinel instead of loader=None for stub detection

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The import machinery overwrites module.__spec__ with the spec returned by
find_spec (which has loader=_StubSubpackageLoader, not None), so the
loader=None check broke for second-level subpackages. Switch to a custom
_unsloth_stub object identity sentinel set directly on each stub module --
it survives __spec__ being replaced and correctly identifies stubs at any
depth (torchao.prototype.safetensors, etc.).
This commit is contained in:
LeoBorcherding 2026-05-11 06:30:04 -05:00
commit 32643198b2
1 changed files with 12 additions and 14 deletions
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26
studio/backend/core/training/worker.py
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@ -1107,16 +1107,17 @@ def run_training_process(
import importlib.machinery as _ilm
import importlib.abc as _ilabc
_STUB_SENTINEL = object() # identity tag placed on every stub module
def _make_mod_stub(mod_name):
m = _types.ModuleType(mod_name)
m.__path__ = [] # marks this as a package to the import system
m.__package__ = mod_name
# importlib.util.find_spec() raises ValueError when __spec__ is None
# on a module that's already in sys.modules (our manually-injected
# stubs). Give every stub a minimal ModuleSpec so find_spec() returns
# a spec object (non-None) instead of raising.
# loader=None is our sentinel: _StubSubpackageFinder uses it to detect
# stub modules and auto-stub their children via the import machinery.
# _STUB_SENTINEL survives __spec__ being replaced by the import
# machinery (which overwrites __spec__ with the spec returned by
# find_spec, breaking the loader=None sentinel we used before).
m._unsloth_stub = _STUB_SENTINEL
# importlib.util.find_spec() raises ValueError when __spec__ is None.
m.__spec__ = _ilm.ModuleSpec(mod_name, loader=None, is_package=True)
def _ga(attr, _m=m, _n=mod_name):
if attr.startswith("__"):
@ -1141,9 +1142,9 @@ def run_training_process(
class _StubSubpackageFinder(_ilabc.MetaPathFinder):
"""Auto-stubs any subpackage import whose parent is one of our stubs.
Identified by parent.__spec__.loader is None (our sentinel). Real
installed packages always have a SourceFileLoader or similar. This
means we never accidentally intercept real subpackage loads.
Uses _unsloth_stub sentinel on the module object — NOT __spec__.loader,
which the import machinery overwrites with the loader from find_spec,
breaking the loader=None check for second-level subpackages.
"""
def find_spec(self, fullname, path, target=None):
if "." not in fullname:
@ -1152,11 +1153,8 @@ def run_training_process(
parent = sys.modules.get(parent_name)
if parent is None:
return None
parent_spec = getattr(parent, "__spec__", None)
if not isinstance(parent_spec, _ilm.ModuleSpec):
return None
if parent_spec.loader is not None:
return None # real module — don't intercept
if getattr(parent, "_unsloth_stub", None) is not _STUB_SENTINEL:
return None # real installed module — don't intercept
loader = _StubSubpackageLoader(fullname)
return _ilm.ModuleSpec(fullname, loader, is_package=True)