If a World War 2 soldier was wounded in combat by enemy fire would they automatically be eligible for a Purple Heart Medal?
Please note that only in the US Army are wounds recognised for an award.
Yes, one receives a Purple Heart for wounds received from enemy fire.
Automatically? Well, the soldier has to report to an aide station. Knowing government and military regulations, I'm sure a form is filled out and this notifies his unit HQ that he was wounded and they issue a citation for a Purple Heart. Here is a personal example.
During enemy shelling in WW2, my father and his Colonel were both nicked by small shell fragments. The Colonel said "Let's go to the aid station and pick up our Purple Heart." My father told the Colonel that he would not set foot in there with a small scratch. He didn't want to dishonor those who really deserved the Purple Heart. Sure enough, I found a GO that showed the Colonel receiving the PH.
This answer only relates to World War 2: The basic unit can award a Purple Heart. The unit would issue a General Order(GO) that stated the date and location that the soldier was cited for the award. Whereas, other medals for bravery would have to be sent up to higher headquarters for approval. The higher the award, the higher the approval is required.