Feature suggestion: Add ModelSelect2Mixin.result_from_instance() method.

[sdolemelipone]

It would be useful to have a way to override or add additional data to the results returned by AutoResponseView for particular widgets.

The use case is processing the select2:select jQuery event on the client side and updating another part of the web page with the related object information. E.g. a ModelChoiceField selects a Product object, and the product's price is rendered alongside the form.

Let me know if this pull request looks acceptable. Thanks

[sdolemelipone]

Oh, and the other use case would be improving performance by using QuerySet.values():

class MyModelWidget(ModelSelect2Widget):
    search_fields = ["name"]
    model = Product

    def filter_queryset(*args, **kwargs):
        return super().filter_queryset(*args, **kwargs).values("pk", "name")

    def result_from_instance(self, obj):
        return {"id": obj["pk"], "text": obj["name"]}

[codingjoe]

Hi @sdolemelipone 👋

Thank you for reaching out. I think you are describing a rather common scenario. I always went ahead and wrote custom views that accompany my widgets. However, I do see a point in using reflection, to only write a widget that includes all extension.

Usually, I'd appreciate a discussion or ticket first, but let's move this along anyway. I didn't do a full review yet, but off the top of my head: Please add the request to the methods context (needed to construct fully qualified URLs or permission management). I also need to be cautious with state leakage. Since the widget is passed between requests, modifications to the widget instance, might propagate to other requests.

Cheers! Joe

[sdolemelipone]

Hi @codingjoe, thanks for taking the time to look at my suggestion. Noted, next time I'll start with a ticket - I found writing the PR interesting so at least no wasted effort on my part there :-).

I'll add the request to the function arguments as you suggested. Regarding the state leakage, this seems like a problem a user could introduce if they did something unusual in result_from_instance(), which involved previous calls to the method - or is there something I'm missing? Is it something that needs to be mentioned in the documentation?

Thanks Mark

[sdolemelipone]

Hi @codingjoe, I've added the request parameter as you suggested. Let me know if there's any other changes you'd like to see. Thanks Mark

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 98.22%. Comparing base (f61b09c) to head (027edb2). Report is 11 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #272      +/-   ##
==========================================
+ Coverage   98.21%   98.22%   +0.01%     
==========================================
  Files           7        7              
  Lines         280      282       +2     
==========================================
+ Hits          275      277       +2     
  Misses          5        5              

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[codingjoe]

cc @syphar

[sdolemelipone]

Great 😃 thanks @codingjoe.