Privatize Widgets.widget

[ianhi]

Closes: #2944

Using such a generic name could lead to collisions with user code as in the linked issue. Here it is changed to a name far less likely to collide with a user subclass and privatized. I'm less sure about making it private but it seems as though doing this will increase future flexibility and clean up what shows up when tab completing on a widget subclass.

I also gave the same treatment to widget_types for consistency.

[jasongrout]

Thanks!

[vidartf]

So is this still safe to be considered "protected" then? I.e. subclasses can rely on this property being available with the current variable name until the next major release ?

[vidartf]

I mean, the fact that the embed code now access a "private" variable seems hacky.

[ianhi]

So is this still safe to be considered "protected" then? I.e. subclasses can rely on this property being available with the current variable name until the next major release ?

I mean, the fact that the embed code now access a "private" variable seems hacky.

My understanding of private variables was that it's ok for anything in the library they are in to use them, including subclasses. In which case it is not hacky for the embed code to access it. Is that different than the canonical view? I'm totally happy to revisit this if you have a suggestion for what a better approach is.

[pllim]

Looks like this was "privatized" without any deprecation period. Broke our code downstream. FYI.

[jasongrout]

Looks like this was "privatized" without any deprecation period. Broke our code downstream. FYI.

Thanks for pointing this out. At the very least, we should note this in the migration documentation.

[maartenbreddels]

Yeah, I think .widgets is used widely, and this will at least break a lot of my code. I understand the change, but maybe we could at least provide a class based getter such as in:
widgetti/reacton@6fb0784

If a subclass decides to use `.widgets', yes it will break code that assumed it to the dict of widgets, but it will make most existing code out there still work.