Bug: fetch in DJ2.0 behaves differently compared to DJ. 0.14

[arturoptophys]

Bug Report

Description

Now that fetch has returned for backwards compatibility. I see 3 differences which might still lead to issues:

1. fetch seems not to be classmethod anymore
2. fetch defaults to as_dict=True in dj.2.0 but was as_dict=False in dj.0.14
3. fetch('KEY') doesnt work

Reproducibility

import numpy as np
import datajoint as dj

dj.conn()  # using datajoint.json
schema = dj.Schema("TEST")

@schema
class RandomLookup(dj.Lookup):
    definition = """
    idx: int32
    ---
    values1: float32
    """
    contents = [(0, 0.0), (1, 1.0), (2, 2.0), (3, 3.0), (4, 4.0)]

RandomLookup.fetch('values1') # works in dj.014

---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
Cell In[38], line 1
----> 1 RandomLookup.fetch('values1')

File ~/datajoint-python/src/datajoint/expression.py:654, in QueryExpression.fetch(self, offset, limit, order_by, format, as_dict, squeeze, *attrs)
    651     return self.to_dicts(order_by=order_by, limit=limit, offset=offset, squeeze=squeeze)
    653 # Default: return structured array (legacy behavior)
--> 654 return self.to_arrays(order_by=order_by, limit=limit, offset=offset, squeeze=squeeze)

AttributeError: 'str' object has no attribute 'to_arrays'

print(isinstance(RandomLookup().fetch('values1')[0],dict)) # True

print(isinstance(RandomLookup().fetch('values1',as_dict=False)[0],dict)) # False

RandomNumbers().fetch('KEY')

---------------------------------------------------------------------------
DataJointError                            Traceback (most recent call last)
Cell In[41], line 1
----> 1 RandomNumbers().fetch('KEY')

File ~/datajoint-python/src/datajoint/expression.py:644, in QueryExpression.fetch(self, offset, limit, order_by, format, as_dict, squeeze, *attrs)
    641 if attrs:
    642     if as_dict or as_dict is None:
    643         # fetch('col1', 'col2', as_dict=True) or fetch('col1', 'col2')
--> 644         return self.proj(*attrs).to_dicts(order_by=order_by, limit=limit, offset=offset, squeeze=squeeze)
    645     else:
    646         # fetch('col1', 'col2', as_dict=False) -> tuple of arrays
    647         return self.to_arrays(*attrs, order_by=order_by, limit=limit, offset=offset, squeeze=squeeze)

File ~/datajoint-python/src/datajoint/expression.py:498, in QueryExpression.proj(self, *attributes, **named_attributes)
    496 # check that all attributes exist in heading
    497 try:
--> 498     raise DataJointError("Attribute `%s` not found." % next(a for a in attributes if a not in self.heading.names))
    499 except StopIteration:
    500     pass  # all ok

DataJointError: Attribute `KEY` not found.

[dimitri-yatsenko]

This was fixed #1375.

[arturoptophys]

Pulled from main, 1 and 2 seem to be fixed. but not 3.

[dimitri-yatsenko]

Working to fix this. #1375 fixed .fetch as a class method, but not "KEY"