DefaultButton with menuProps does not obey style={{width: '100%'}}

[Ofer-Gal]

I want to steratch the split button to take all the containing width on a web part but it keeps the width based on the text of it.
Is there a property in the menuProps to apply style={{width: '100%'}} ?

Thank you

[micahgodbolt]

Due to the complex nature of the split button (two buttons wrapped in a span) we have a specific style target for getting CSS onto the container. The style tag you are using, applies styles to the primary button, to target the split button container, use the following:

<DefaultButton
        styles={{ splitButtonContainer: { width: '100%' } }}
        text="Standard"
        split
      />

[Ofer-Gal]

That is a start. it shows something mid way to 100%. Could the problem be that the row it is in is display: 'flex' ? I am not using Stacks like the demo shows.