Fixed "allowClear" when no "placeholder" is set (AssociationField)

[liarco]

When trying to clear an AssociationField I get an error from Select2:

This seems to be related to: https://stackoverflow.com/questions/49953467/cannot-read-property-id-of-undefined-select2
Select2 doc: https://select2.org/selections#clearable-selections

My solution: I simply check if allowClear is set (and true), then if placeholder is not set I set it to an empty value.

I tried to fix this in a simple way, but maybe you prefer a different solution, let me know.

Thank you for your time.

[liarco]

@javiereguiluz I'm afraid that #3925 introduced this regression. And now I think that my solution might not be enough since the bug also affects other Select2 inputs like the ChoiceField (does it use the same CrudAutocompleteType?).

If you have any preferred solution I can implement it and update this PR.

Thank you!

[javiereguiluz]

@liarco I saw this error a few days ago in one of my apps ... but now I cannot reproduce it anymore. Could you please update to the latest dev-master changes and see if the error is gone. I'm probably missing something, but let's double check. Thanks!

[liarco]

Hi @javiereguiluz, I tested using a1d8c1d and now association inputs with ->autocomplete() don't set data-allow-clear correctly.

I'm testing a brand new entity with a property which can be null, if I don't enable lazy-loading then the clear option works as intended (but I think it's because Select2 finds real options inside the <select> element), if I enable lazy-loading the x button disappears...

Forcing the data-allow-clear setting the attr option fires the same error as before.

Please let me know if there's anything else I can do to help you troubleshooting.

[javiereguiluz]

Thanks for the new insights and the perfect GIF showing the problem. LEt's merge this! Thanks!