get_x_argument(as_dictionary=True) fails if x values doesn't have =

[iurisilvio]

Describe the bug

It is not safe to use get_x_argument(as_dictionary=True) because it fails with -x foo.

Expected behavior

I'd expect an empty string "" (or True? or None?) as value instead of breaking my script.

To Reproduce

from unittest.mock import Mock

from alembic.config import Config
from alembic.runtime.environment import EnvironmentContext
from alembic.script import ScriptDirectory

context = EnvironmentContext(Config(cmd_opts=Mock(x="foo")), ScriptDirectory("."))
context.get_x_argument(as_dictionary=True)

Error

$ python example.py
Traceback (most recent call last):
  File "example.py", line 8, in <module>
    context.get_x_argument(as_dictionary=True)
  File "alembic/runtime/environment.py", line 331, in get_x_argument
    value = dict(arg.split("=", 1) for arg in value)
            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
ValueError: dictionary update sequence element #0 has length 1; 2 is required

Versions.

• OS:
• Python:
• Alembic:
• SQLAlchemy:
• Database:
• DBAPI:

Additional context

Have a nice day!

[CaselIT]

Hi,

Thanks for reporting

I'd expect an empty string "" (or True? or None?) as value instead of breaking my script.

Yes, I think an empty string is the least surprising value here

[zzzeek]

Yes, I think an empty string is the least surprising value here

hmm not None? what do we do if someone asks for x value and there was no -x ?

[CaselIT]

Yes, I think an empty string is the least surprising value here

hmm not None? what do we do if someone asks for x value and there was no -x ?

Well if foo=bar gives me 'bar' it think the logic thing for foo= and foo is to return ''. Otherwise we have two different behaviours in that case

[zzzeek]

Yes, I think an empty string is the least surprising value here

hmm not None? what do we do if someone asks for x value and there was no -x ?

Well if foo=bar gives me 'bar' it think the logic thing for foo= and foo is to return ''. Otherwise we have two different behaviours in that case

oh ok. that's fine then

[iurisilvio]

This is how I think too, foo= generate an empty string, foo should return the same value.

Talking about my use case, I just need something like multiple tags and I don't really care about the value.

I don't even need the dict. I could use "foo" in context.get_x_argument(), but then I can't use as_dictionary flag anywhere else because foo breaks it.

In any case, we still can check for the key with "foo" in context.get_x_argument(as_dictionary=True).

[sqla-tester]

Iuri de Silvio has proposed a fix for this issue in the main branch:

Fix get_x_arguments(as_dictionary=True) for args without = https://gerrit.sqlalchemy.org/c/sqlalchemy/alembic/+/4989