On Thu, Mar 5, 2020, at 12:02 PM, Daniel Cardin wrote:
> So, yes I mean "commands" as in `alembic.command.upgrade()`.
>
> The idea would be that the library defines an env.py (e.g. the important
> portion of which would look something like:)
> ...
>
> connectable = context.config.attributes.get("connection", None)
> with self.connection.connect() as connection:
> alembic.context.configure(connection=connection)
>
> with alembic.context.begin_transaction():
> alembic.context.run_migrations()
>
> which lives at `src/library/foo/env.py`. If the migrations were colocated
> with the env.py, then afaik setting "script_location" to "library:foo" would
> enable me to run `alembic.command.upgrade()` and it would just work. However
> in this case (if possible), the migrations/versions/* would live at an
> arbitrary other location (e.g. the code which has installed this library).
Ok two thoughts on that:
1. usually the way this goes is that the project that has the migrations does
everything normally, it has its own env.py, and inside that env.py, that's
where it imports *your* env.py. that is, instaed of having the usual env.py it
would only have:
# env.py
from daniel_cardins.library.env import run_migrations
run_migrations(<important arguments>)
2. the locations of the version files vs. the env.py script are actually
separate in the config. there is a script_location that it uses to find the
home base where env.py is, however there is also a version_locations config
that can have any number of other directories in it and these supersede
script_location for the version files themselves.
I think in general, if the end-user has a bunch of version files set up, it's
probably not a big deal that they have a stub "env.py" right there that just
calls out to your library. that's something very clear that people looking at a
project that uses your library can understand quickly if they already know
alembic.
>
> General workflow:
> * person working on project "foo" invokes some cli/command/whatever which
> requests an upgrade
> * library does whatever requisite setup
> * library invokes `alembic.command.upgrade()`
> * upgrade() ends up routing the code through the library's `env.py`
> * the context of the migration command is targeting the project "foo"'s local
> migrations/versions folder
>
> The specifics of the above are just based on my knowledge of alembic, so if
> there's another process i could be doing where env.py isn't "invoked" so much
> as the above code block is just called normally, then that's ideal.
>
> On Thursday, March 5, 2020 at 9:36:09 AM UTC-5, Mike Bayer wrote:
>>
>>
>> On Thu, Mar 5, 2020, at 8:08 AM, Daniel Cardin wrote:
>>> I am attempting to write a library which invokes alembic commands, while
>>> referencing the migrations of a separate package which has installed said
>>> library.
>>>
>>> The intent here, is for the library to invoke the alembic commands with an
>>> env.py defined in that package. This seems to work through
>>> config.get("script_location", "package_name:foldername")
>>> but then obviously expects the actual migrations to be colocated at the
>>> same location.
>>>
>>> My guess would be, if this is possible at all, that there'd be something I
>>> could put in the env.py which would reconfigure it to execute the
>>> `context.run_migrations()` migration context (and therefore search path,
>>> back at the original call site.
>>>
>>> I realize that this won't always work, given that env.py is often likely
>>> customized enough such that a generic one wouldn't be able to execute them,
>>> but per your cookbook suggestions about programmatic invocation of
>>> commands, this sort of thing requires the user to opt into changing their
>>> env.py to use
>>> connectable = context.config.attributes.get("connection", None)
>>> in order to make use of a connection handed to it.
>>
>> I'm not following all the moving pieces here, like when you say "commands",
>> i assume you mean the commands in alembic.command, , like
>> alembic.command.upgrade(). when you say "an env.py defined in that package",
>> I guess you mean in the separate package that is using your library.
>>
>> this doesn't seem different from what Alembic itself does, "that package"
>> would have a directory where the env.py and its migration files are present?
>> So... I'm not really sure what you're trying to do beyond call an Alembic
>> command that is against a particular directory.
>>
>> if OTOH by "commands" you mean migration operations, like you want to call
>> op.create_table() yourself, OK, but I don't really understand enough to
>> formulate an answer for you.
>>
>>
>>
>>
>>>
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