Fix Orchestrator.__repr__ crash on partially-initialized instances

[gospartan]

Summary:
Fix AttributeError in Orchestrator.__repr__() when the object is only
partially initialized. The method checked hasattr(self, "experiment") but
did not check hasattr(self, "generation_strategy"), causing a crash when
__repr__ was called between the two attribute assignments.

Bug details:

Orchestrator.__init__ sets attributes in this order:

self.experiment = experiment           # line 228
self._set_logger(options=options)      # line 231
self.options = options                 # line 232
self.generation_strategy = generation_strategy  # line 235

If any error occurs between lines 228-235 (e.g. in _set_logger), then
self.experiment exists but self.generation_strategy does not.

The log_usage() decorator on OrcOpticsScheduler.__init__ catches such
errors and calls repr(args) to log them. Since args[0] is the partially-
initialized scheduler instance, this triggers Orchestrator.__repr__():

def __repr__(self) -> str:
    if not hasattr(self, "experiment"):       # True -- experiment IS set
        return f"{self.__class__.__name__}"
    return (
        f"...generation_strategy={self.generation_strategy}..."  # BOOM
    )

The secondary AttributeError replaces the original error, making the real
failure impossible to diagnose.

Example: FBLearner run f1051747930 failed with:

AttributeError: 'OrcOpticsScheduler' object has no attribute 'generation_strategy'

Stack trace: OrcOpticsScheduler.__init__ -> Orchestrator.__init__ ->
(error between lines 228-235) -> log_usage error handler ->
repr(args) -> Orchestrator.__repr__ -> self.generation_strategy crash.

The actual root cause was completely masked by this __repr__ bug.

Fix: Add hasattr(self, "generation_strategy") guard alongside the
existing hasattr(self, "experiment") check.

Differential Revision: D97166104

[meta-codesync]

@gospartan has exported this pull request. If you are a Meta employee, you can view the originating Diff in D97166104.

[meta-codesync]

This pull request has been merged in 5bff9c3.