Custom optimization functions are called twice, once without scheduler kwargs. #6381
Description
Custom optimization functions (those given as a scheduler optimizations=[foo] kwarg or set in the Dask config) are being called twice: the first time without scheduler kwargs, the second time with scheduler kwargs.
In [1]: import dask
...: import dask.array as da
...: import numpy as np
In [2]: def dummy_opt(dsk, keys, **kwargs):
...: print(f"Called with kwargs: {kwargs}")
...: return dsk
In [3]: da.from_array(np.array([1, 2])).compute(optimizations=[dummy_opt], dummy_kwarg="foo")
Called with kwargs: {}
Called with kwargs: {'dummy_kwarg': 'foo'}
Out[3]: array([1, 2])This bug was introduced in this large performance-oriented PR, and affects the following versions: 2.20.0, 2.19.0, 2.18.1, 2.18.0, 2.17.2, 2.17.1, 2.17.0, and 2.16.0.