Fix @app.param and @app.header producing invalid Swagger/OpenAPI document

[Drarok]

Only include description in param and header when it has a value, else the resulting document fails validation

[coveralls]

Coverage increased (+0.002%) to 96.83% when pulling a3c9114 on Drarok:fix/invalid-param-description into e911078 on noirbizarre:master.

[j5awry]

Can you provide the open issue this is in relation to? And/or recommended test cases?

Also, we'd greatly appreciate if unit tests could be added. If you're not sure where, we can help guide on that. Minimally we need steps to reproduce the error so we can test the fix.

[Drarok]

There's no open issue at present, it's something I noticed was incorrect when trying to validate the swagger.json for our API.

I'll have a look at producing a test case, but unless there's already something validating against the Swagger schema, it might be a lot of work. I can assert that description isn't null (which is what the problem is) directly, but I don't know if that's official enough?

That said, I've found the contributing docs and they appear to be incorrect:

pip install -e .[dev]
zsh: no matches found: .[dev]

[Drarok]

To put it briefly, the description key on a parameter must be a string, so null is invalid: https://swagger.io/specification/#parameterObject

I verified this using an online validator