Adding bill types and automatic settling between people

[TomRoussel]

Summary

This PR is a continuation of #1116. The goal of this PR is to finish the work of the original PR and fix #137. The overall design changes proposed in #1116 are mostly kept, though I'll detail the changes below. This PR adds a button to the "Settle" page to automatically let users signify they have settled their debt with other people. This generates a new bill in the overview page that will bring their debt with that person to 0.

Normally this would pollute the statistics of that project, so a bill_type column is added to the database. There are 2 types, "Reimbursement" and "Expense", only the latter is used to calculate the total cost of the project.

Changes since the original PR

• Brought the FlowingCloudRTL branch up to speed with the current master
• Worked in the minor suggested changes by @Glandos
• Changed the "bill_type" column to use an Enum (as requested by @Glandos). This enum is also used by the bill form validator
• Removed the "Transfer" bill type. Personally I don't see a use for it and it seems confusing to the user. In the original PR, there didn't seem to be any interest in keeping it around
• Added an api test to check if bill_type is validated correctly

Open questions

With these changes, all bill creation requests to the API require that a "bill_type" is provided. This will break compatibility with apps using the API. Should we make the "bill_type" field an optional parameter? I think we can safely make the default type be "Expense".

[almet]

Hey, thanks for your work on this.

With these changes, all bill creation requests to the API require that a "bill_type" is provided. This will break compatibility with apps using the API. Should we make the "bill_type" field an optional parameter? I think we can safely make the default type be "Expense".

+1 for this being the default behaviour.

[TomRoussel]

Okay, I'll make bill_type an optional parameter to the bill adding API then and get back to you when that's ready!

[TomRoussel]

Done, bill_type is now "Expense" by default, and this default is now applied to all existing bills as well.

[almet]

Thanks for the follow up on this. On my end, it seems good. I took another glance at your changes and added a few remarks. We're almost there!

[almet]

Tests are currently failing on postgres, because it tries to use a unknown type:

psycopg2.errors.UndefinedObject: type "billtype" does not exist
E       LINE 1: ALTER TABLE bill ADD COLUMN bill_type billtype DEFAULT 'EXPE...

(The tests run otherwise properly when using sqlite)

[TomRoussel]

Oh weird, I'll have a look this weekend to see why it's doing that.

[TomRoussel]

Turns out alembic does not handle the generation of new enums correctly for postgres databases. See this issue.

I fixed it by manually creating the sqlalchemy enum in the upgrade step of the migration, as someone suggested in the issue I linked. In that issue someone also introduced a library that handles enum migrations in alembic automatically: alemibc-postgresql-enum, but I didn't want to add a new dependency for this small issue :).

Hopefully the tests are green now! It seemed to work on a postgres database I spun up locally.

[almet]

Perfect, thanks :-)

[almet]

Thanks for the work on this 👍

[almet]

It was a pleasure to work with you :-)

[TomRoussel]

Same here!

[TomRoussel]

Sure, I'll go through those comments and submit a new PR! I'll probably have time to have a look in the weekend, though no promises.

You just use python-black on the whole codebase? Then I'll make sure to run it along with the suggested changes.