Add optional parameter to sort nulls last

[lbeaufort]

Summary (required)

• Resolves Add ability to sort nulls last #3470: Add optional "NULLS LAST" (sa.nullslast) sort

Currently, nulls will sort last by default when sorting ascending - this feature adds an optional sort_nulls_last parameter which forces nulls to the bottom for descending sort. The default behavior of the API is unchanged. This is needed for proper display of front-end data tables.

How to test the changes locally

• Test this link with the default behavior. Nulls should show first: http://127.0.0.1:5000/v1/candidates/?api_key=DEMO_KEY&sort_hide_null=false&has_raised_funds=true&sort=-first_file_date&per_page=30&page=1
• Add the sort_nulls_last=true parameter and nulls should appear on the last page instead of the first page: http://127.0.0.1:5000/v1/candidates/?api_key=DEMO_KEY&sort_hide_null=false&has_raised_funds=true&sort=-first_file_date&per_page=30&page=1&sort_nulls_last=true

Impacted areas of the application

List general components of the application that this PR will affect:

• Needed for proper display of data tables (Sort nulls last in data tables fec-cms#2491)

Related PRs

fecgov/fec-cms#2488
fecgov/fec-cms#2491

[codecov-io]

Codecov Report

Merging #3474 into develop will increase coverage by <.01%.
The diff coverage is 100%.

@@             Coverage Diff             @@
##           develop    #3474      +/-   ##
===========================================
+ Coverage    88.67%   88.67%   +<.01%     
===========================================
  Files           76       76              
  Lines         6323     6325       +2     
===========================================
+ Hits          5607     5609       +2     
  Misses         716      716

Impacted Files	Coverage Δ
webservices/sorting.py	88.33% <100%> (+0.4%)	⬆️
webservices/utils.py	91.66% <100%> (ø)	⬆️
webservices/args.py	97.52% <100%> (ø)	⬆️

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[fec-jli]

It works great.
one question. Can we set sort_nulls_last=True as default value? most of our cases want to sort_nulls_last=True? right? Thanks

[lbeaufort]

Thanks for taking a look @fec-jli! While that’s my preference, I didn’t want to change the default behavior of the API - it’s arguably a breaking change to do so.

[lbeaufort]

This CMS PR will default the front-end data tables to always sort nulls last:
fecgov/fec-cms#2491

[fec-jli]

It works great. Thanks

[qqss88]

tests look good.

I am a little confused on those 2 arguments:
'default_sort_nulls_last=False, sort_nulls_last=False'- it seems like 'sort_nulls_last' is not used in the function.

It's good to add some doc string to the function we modified.

[lbeaufort]

@qqss88 that's a good catch, thanks! They were unused so I removed them with my latest commit. I should have time to add docstrings, but I want to make sure I get my other issue for this sprint addressed first.