Support for serialization of `functools.partial` objects in migrations

[Piper Merriam]

It would be nice for the django migration engine to support serialization of functools.partial objects. I don't see any obvious barriers to this beyond adding additional logic to the MigrationWriter.serialize method to handle objects of that type.

A general description of the approach that seems appropriate is as follows.

For an object x which passes the check isinstance(x, functools.partial)

• perform MigrationWriter.serialize(x.func) to get the serialized function string and imports.
• perform MigrationWriter.serialize(x.args) to get the serialized positional arguments that have been curried.
• perform MigrationWriter.serizlize(x.keywords) to get the serialized keyword arguments that have been curried.
• construct the string to reproduce the partial object with something like "functools.partial({0}, *{1}, **{2})".format(func_str, pos_args_str, keyword_args_str)

Is this functionality desired and worth supporting?

[Piper Merriam]

Here is a branch in my fork that implements this functionality. Should I open a pull request?

​https://github.com/django/django/compare/master...pipermerriam:piper/suppor-functools-partial-serialization

[Carl Meyer]

It's a useful feature and the implementation is straightforward. I'm in favor of including it.

I have a question about the code, but I'll wait and comment on the pull request once you open it. Thanks for the contribution!

[Piper Merriam]

Replying to carljm:

It's a useful feature and the implementation is straightforward. I'm in favor of including it.

I have a question about the code, but I'll wait and comment on the pull request once you open it. Thanks for the contribution!

Pull request for comment ​https://github.com/django/django/pull/5061

[Tim Graham]

Looks good, pending some cosmetic comments.

[Tim Graham <timograham@…>]

In 537818a:

Fixed #25185 -- Added support for functools.partial serialization in migrations