Unexpected behaviour in v6.0.1 - Feature.getStyle()

Describe the bug In version 5.3.0 Feature.getStyle() returned an object, in version 6.0.1 it’s now returning a function.

To Reproduce Steps to reproduce the behavior:

1. Create a Feature and render it on the map.
2. Get the feature using VectorSource.getFeatureById().
3. Try to extract the style from the feature using Feature.getStyle().

Expected behavior Previously it returned an object upon which I could call setImage() for instance.

More information After debugging some more it appeares it returnes a function that is stored in the variable style_ on the feature object. This function seams to be a static function that expects a feature as it’s parameter. When using that function and passing on the feature as a parameter i get an array of style objects back. In my case it only has one style on position 0. Something like this: const style = feature.getStyle()(feature)[0] Or more readable:

const getStyleFunction = feature.getStyle();  
const stylesArray = getStyleFunction(feature);  
const style = styleArray[0];

Instead of previously: const style = feature.getStyle()

[mike-000]

ol/interaction/Select does test if (this.style_) { but it is meaningless because the initialisation

this.style_ = options.style ? options.style : getDefaultStyleFunction();

should be

this.style_ = options.style !== undefined ? options.style : getDefaultStyleFunction();

null or false could then be specified to prevent overriding the style

[mike-000]

The above would still need to be documented. Previously a Select style only overrode a layer style. If the feature already had a style that had precedence. Backward compatibility could be maintained if the Select only sets its style on a selected feature if the feature has no style, and resets it to undefined when a feature is deselected.