demo select bug

[benwilson512]

I have added :foo and :bar virtual columns to User. In the form, :foo is controlled by a selector with options A => a, B => b.

Also in the form, :bar is displayed with both a text field and a selector with the same options.

When I click on the selector to make a change to :foo, the validate callback in the live view also makes a change to :bar to set it the same as :foo: https://github.com/chrismccord/phoenix_live_view_example/pull/39/files#diff-ba686f7f18e067a11567b119ec1695e5R26

This is reflected in the :bar text field, but the :bar select tag does NOT change. If you IO.inspect the rendered form, you'll find that it is not sending selected on that option row for some reason.

This seems like a bug, since it makes it impossible to control select values from the backend. I'm happy to look into it but I'm having trouble finding where that logic exists.

[benwilson512]

OK I figured out why this is happening, but I don't know if what's happening is what should happen.

selected logic is here: https://github.com/phoenixframework/phoenix_html/blob/master/lib/phoenix_html/form.ex#L1121. If value is not set explicitly, selected/3 gives priority to the params https://github.com/phoenixframework/phoenix_html/blob/master/lib/phoenix_html/form.ex#L1131.

It only falls back to input_value if there are no params for that field name.

This means that I can get the behaviour I want by doing:

<%= select f, :bar, @options, value: Ecto.Changeset.get_field(f.source, :bar) %>

This is counterintuitive though because all generic inputs just use the input_value function, which puts priority on the changeset.