Can Primal Savagery be used as a reaction with the War Caster feat?

Question

My druid player has just taken the War Caster feat, which states (from the PHB):

When a hostile creature's movement provokes an opportunity attack from you, you can use your reaction to cast a spell at the creature, rather than making an opportunity attack. The spell must have a casting time of 1 action and must target only that creature.

In combat, she attempted to use Primal Savagery as a reaction when given the opportunity for an opportunity attack. For Primal Savagery (from XGtE):

• Casting Time: 1 action
• Range/Area: Self
• Components: S
• Duration: Instantaneous

You channel primal magic to cause your teeth or fingernails to sharpen, ready to deliver a corrosive attack. Make a melee spell attack against one creature within 5 feet of you. On a hit, the target takes 1d10 acid damage. After you make the attack, your teeth or fingernails return to normal.

I allowed it during the session because it seems to generally fit with the spirit of War Caster, but after a closer look I'm curious. War Caster needs to target the hostile creature, and Primal Savagery is technically targeting the self before delivering an attack. Right now at level 12, Primal Savagery does 3d10 on a hit without consuming a spell slot, so it's not negligible (though not an enormous issue).

Does Primal Savagery work with War Caster as written?

(Note: This is quite similar to this question about Bigby's Hand but I feel that the difference is that Primal Savagery can be used to only hit one target.)

Answer 1

Primal Savagery targets two creatures.

Primal Savagery has a range of self, so you are one target, and it targets another creature, for a total of two targets. Since War Caster stipulates that the spell must target only one creature, Primal Savagery is ineligible.

Primal Savagery isn’t better than other War Caster eligible cantrips, so just let it work.

Primal Savagery is pretty standard as far as cantrips go. It isn’t like it will be OP with War Caster where other cantrips would be balanced. Strictly rules-as-written, it doesn’t work, but it shouldn’t cause problems.