fix issue where Set.delete_uploaded_files removes files it should not…

[leonelcamara]

… during an update

The change I made differentiates between updates and deletes by taking advantage of upload_fields always being None in the case of deletes. If it is an update it only deletes the file if the field with it was updated and the new value is different.

See:
https://groups.google.com/forum/#!topic/web2py-developers/gwEr1cHQNAY

[leonelcamara]

I'm still not sure this is the complete fix as it is possible that an update causes compute fields to change and they will not appear in upload_fields, causing the file to not be deleted.

My second commit fixes this problem however it causes some fields to be computed twice, any suggestion?

[codecov-io]

Current coverage is 65.75% (diff: 30.00%)

Merging #429 into master will decrease coverage by 0.02%

@@             master       #429   diff @@
==========================================
  Files            69         69          
  Lines          8912       8918     +6   
  Methods           0          0          
  Messages          0          0          
  Branches       1949       1950     +1   
==========================================
+ Hits           5862       5864     +2   
- Misses         2546       2549     +3   
- Partials        504        505     +1   

Powered by Codecov. Last update 4d22bb4...edd508b

[gi0baro]

@leonelcamara why changing this whole block of code to avoid a continue?

[gi0baro]

@leonelcamara @mdipierro @niphlod can I start a discussion about computed fields before merging this?

I would like to change the whole logic of how computed fields are computed during inserts/updates 'cause for example we still can't use them in callbacks (see emmett-framework/emmett#151 for example). May I produce a bigger PR including this fix? What do you think?

[niphlod]

The more streamlined the better

[gi0baro]

@niphlod what do you mean by streamlined? :)

[leonelcamara]

I would like to change the whole logic of how computed fields are computed during inserts/updates 'cause for example we still can't use them in callbacks (see emmett-framework/emmett#151 for example). May I produce a bigger PR including this fix? What do you think?

@gi0baro sure, I think we need to discuss computed fields, because although this PR fixes a problem it is not efficient. Fields with a compute should probably have a required_fields for instance.

[niphlod]

Streamlined as in "we know current has drawbacks and we'll think about fix it once and for all" :-P

[mdipierro]

@leonelcamara @gi0baro this PR now has conflicts with the one that was merged. Can you please help resolve those?

[gi0baro]

@leonelcamara @mdipierro I close this since is already fixed by #431

[mdipierro]

thanks!