Relative path for script_location in alembic.ini

[lorenabalan]

Hi team! 👋 I've encountered some surprising behaviour while working with Config and ScriptDirectory and would like to check if it's intentional or if there's scope for a fix.

I have collection of alembic directories each with their own alembic.ini files, their own migration folders, and some custom files. I was trying to programmatically check if there are multiple heads for a given directory.

path_to_ini_file = Path(...) / "alembic.ini"
config = Config(path_to_ini_file)
script_dir = ScriptDirectory.from_config(config)

heads = script_dir.get_heads()

However, I noticed that script was looking at the wrong place! My alembic.ini file contains

[alembic]
script_location = ./

It was looking into ./versions relative to the location where the Python script lives, not in the ./versions relative to where the alembic.ini file lives.

My workaround was

    path_to_migration_directory = Path(...)  # where the versions/ folder lives

    config = Config()
    config.set_main_option("script_location", str(path_to_migration_directory.resolve()))
    script_dir = ScriptDirectory.from_config(config)

    heads = script_dir.get_heads()

I tracked it down to this line which leads to setting ScriptDirectory().dir to naive ./, rather than relative to the location of the alembic.ini. Is it possible to make either the ScriptDirectory or the Config class smarter when parsing the script_location config? Or is it expected behaviour and I should live with the workaround? Or are we meant to only have absolute paths in alembic.ini?

[zzzeek]

However, I noticed that script was looking at the wrong place! My alembic.ini file contains

[alembic]
script_location = ./

It was looking into ./versions relative to the location where the Python script lives, not in the ./versions relative to where the alembic.ini file lives.

oh, I've never heard of systems assuming the absolute location of the ini file is where "." should be. as documented we support the %(here)s symbol, which is how this is set explicitly for .ini files:

[alembic]
script_location = %(here)s/

it's not a dot but that will give you the absolute path of where your .ini file is.

[lorenabalan]

Oooh I see. We don't use %(here) anywhere but that looks like what I need! Thanks a bunch. 🙌