Photoshop how to fill only inside selection of a circle?

Question

There is a simple circle (but can me any shape object with transparent area inside) on transparent background.

If I use magic wand tool to create a selection, it creates:
a/ outside selection
b/ inside selection

Question:
What is the fastest way to fill only inside selection with solid color (to automate process)?

Other solution:
Instead of quick selection tool use:
c/ magnetic lasso tool - it create inside selection only, to fill inside only
d/ pen tool - the same but slow
e/ path operations

Solution c/d/ is not good if I wanna automate process.
Solution e/ steps:

1. quick selection tool creates outside selection and inside selection,
2. make work path from selection,
3. it creates outside path and inside path,
4. if I wanna continue with inside path only, I have to modify work path with Path operations:
   change option to "Intersect shape areas",
   
5. now I can fill work path with color, which fill inside selection only. Great! But...
   
   Problem of e/ solution:
   Recorded action for e/ solution fails at:
   4/change option in Path operations to "Intersect shape areas" - recorded action is not able to remember this settings, so action does not fill area inside path. It always use another unwanted option from Path operations. (reset PS settings etc did not help).
   
   I did not find script or action or any solution how to swich options in Path operations or how to activate specific option in Path operations (combine, subtract, intersect...).
   I bet there is one so simple solution which I am blind to see atm.
   The best one for me is to find way how to activate specific option in Path operations (combine, subtract, intersect...) and use it in script/Action whenever.
   Thank You all for any creative ideas!

Answer 1

I'm really not sure whether you are over-thinking it, or I'm under-thinking it, however...

Use the Paint Bucket Tool.
Set the tool to Contiguous, All Layers*.

Click inside the circle…

*All Layers covers for if you have the shape as a vector on a different layer - as you can't paint on a vector layer (though, of course, you could fill it instead.)