alter support for part tables

[ixcat]

Bug Report

Description

Alter on part tables yields 'datajoint.errors.DataJointError: Foreign key reference master could not be resolved'

Reproducibility

Via support ticket 151 ; reproduced on linux / dj 0.13.3 / py 3.8 using:

import datajoint as dj

schema = dj.schema('test_fooparts')

@schema
class Foo(dj.Manual):
    definition = '''
    foo_id: int
    '''

    class SubFooOne(dj.Part):
        definition = '''
        -> master
        subfoo_id: int
        '''

followed by:

>>> Foo.SubFooOne().alter()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/src/djc/datajoint-python/datajoint/table.py", line 104, in alter
    sql, external_stores = alter(self.definition, old_definition, context)
  File "/src/djc/datajoint-python/datajoint/declare.py", line 360, in alter
    table_comment, primary_key, attribute_sql, foreign_key_sql, index_sql, external_stores = prepare_declare(
  File "/src/djc/datajoint-python/datajoint/declare.py", line 248, in prepare_declare
    compile_foreign_key(line, context, attributes,
  File "/src/djc/datajoint-python/datajoint/declare.py", line 143, in compile_foreign_key
    raise DataJointError('Foreign key reference %s could not be resolved' % result.ref_table)
datajoint.errors.DataJointError: Foreign key reference master could not be resolved

Expected Behavior

Unclear if master/part support is included in alter yet (alter is experimental); filing for reference to track capability

[rly]

A workaround for this is to not use the "master" keyword in the Part table definition and instead reference the name of the master table. e.g., in your example:

        definition = '''
        -> Foo  # instead of master
        subfoo_id: int
        '''