Enable CharWidget to return string

[matthewhegarty]

Problem

Issue #1573.

This adds options to force CharWidget to return its values as strings. This seems logical because the other widgets use clean() to return their values as underlying types.

However, this could break existing implementations, so I have preserved the current default behaviour, and made it optional to return values as strings, also handling the 'null' case either as empty string or as None.

Maybe we will make this mandatory behaviour of CharWidget in a future release.

Solution

• Updated constructor to accept kwargs
• Modified clean()

Acceptance Criteria

Full unit tests added.

[pokken-magic]

This makes a lot of sense to me as an option. It might make sense to create it as a Resource level field that supplies this to all charwidgets as well - I always find it helpful to be able to set global values. It's especially useful for Excel and CSV that don't really have the same concept of null as Json and Yaml do.

Not 100% sure what the pattern should be for things with types like json and Yaml in the future, but it might make sense for the default behavior to only be for CSV/Excel formats to make strings.

[matthewhegarty]

Hi Ryan
Thanks for reviewing so quickly. Some great points you make there.

It might make sense to create it as a Resource level field that supplies this to all charwidgets as well - I always find it helpful to be able to set global values.

Yes, I think I would implement this at the settings level (in fact, that might be better than as kwargs because like you say it would likely be a global setting). Although I think having both would give the flexibility.

I will likely put this into release 3.4.0 and see if we get any feedback.

[coveralls]

coverage: 100.0%. remained the same when pulling f4bc4d3 on matthewhegarty:issue-1573-CharWidget-return-str into 65f0085 on django-import-export:main.