[ENH] OWSelectAttributes: Use input features

[VesnaT]

Issue

Enable filtering dataset using selected features.
Implements #3300

Description of changes

• Upgrade Select Columns widget to accept Features on the input (as AttributeList). One can choose between using input features and data domain features to obtain output data. New button "Use input features" is added for this purpose. When features appear on the input, the button enables. After the features have been used, the "Features" list box disables.
  The initial state is can be obtained by clicking "Reset" button.

• Upgrade Rank widget to output Features (as AttributeList).

Includes

• Code changes
• Tests
• Documentation

[codecov-io]

Codecov Report

Merging #3299 into master will increase coverage by 0.07%.
The diff coverage is 100%.

@@            Coverage Diff            @@
##           master   #3299      +/-   ##
=========================================
+ Coverage   82.12%   82.2%   +0.07%     
=========================================
  Files         351     351              
  Lines       62122   62334     +212     
=========================================
+ Hits        51017   51240     +223     
+ Misses      11105   11094      -11

[janezd]

Works as intended, except for one thing: the push button disables the list view, so the only way to get out of this is to use the Reset button. Only the checkbox should disable the view. See the code I propose below.

I like it that the button is enabled exactly when it would actually do something.

I don't like the GUI we decided upon: the checkbox and the push button now dominate the widget. As much as I prefer disabling instead of hiding, I lean towards disabling it when input features are not present.

The remaining comments I wrote are just nitpicking. Use or ignore at will.

[janezd]

I suppose I would want to have the list view disabled only when checkbox is checked:

         if self.use_input_features and self.can_use_features():
             self.use_features()
            self.enable_used_attrs(False)
        else:
            self.enable_used_attrs()

Otherwise, pushing the button disabled the list view and buttons, and the only action that gets me out of this is the Reset button.

[janezd]

For the same reason as above, in __use_features_changed, I think the above line should be removed. Pushing the button should keep the list view enabled, otherwise the only option to re-enable it is the Reset button.

[janezd]

On the first glance, I thought that this method checks whether the features on the input are usable. I don't have a better name. Perhaps can_enable_use_features? I don't like it, but it tells me what it does.

[janezd]

This name confuses me, too. Perhaps __on_use_features_checkbox? Not too nice, either, but I understand it.

[janezd]

You can also do:

def check_data(self):
    self.Warning.mismatching_domain(
        shown=self.data is not None
        and self.features is not None
        and not self.features_from_data_attributes
    )

[janezd]

It is a matter of taste, but consider avoiding repeating domain[feature.name] by

return [var
        for var in (domain[feature.name]
                    for feature in self.features if feature.name in domain)
        if var in domain.attributes]

or

existing = (domain[feature.name] for feature in self.features
            if feature.name in domain)
return [var for var in existing if var in domain.attributes]

On the other hand, isn't this the same as

attrs = {attr.name for attr in domain.attributes}
return [domain[feature.name] if feature.name in attrs]

assuming that all names are unique?

[janezd]

I didn't realize you can repurpose gui.auto_commit for this. I assumed there can be only a single auto_commit control per widget. :) Nice.

[janezd]

Since self.features_from_data_attributes is a list, PEP8 recommends if self.use_input_features and self.features_from_data_attributes

[janezd]

Are you sure that these repaints (here and in the next function) are needed? It seems to work without for me.

[janezd]

Perhaps self.use_features_box.setHidden(not enable_checkbox) (see the general comment).