Does a Melee spell attack count as a Weapon attack?

Question

I'm relatively new to D&D and I've been thinking through on some builds when I thought about something I strangely hadn't thought of for a while; Ranger, specifically Horizon walker, Planar Warrior.

As a bonus action, choose one creature you can see within 30 feet of you. The next time you hit that creature on this turn with a weapon attack, all damage dealt by the attack becomes force damage, and the creature takes an extra 1d8 force damage from the attack.

Now the question...

Do melee spell attacks count as a weapon attack? Or do they have to be explicitly stated in the spell ' Make a Melee weapon attack' I.E. Booming blade?

Answer 1

Unless a Weapon Attack is Specified as Part of It, No

You have it right at the end of your question. A few spells make a melee weapon attack as part of the attack (Booming Blade for example), but otherwise a melee spell attack is not a weapon attack.

However, the Ability in Question is Not a Spell Attack in Any Case

Abilities, even magical ones, are not spells (much to the joy of eccentric Barbarian multiclasses). The Planar Warrior ability you cite is simply an ability to magically buff the weapon attack you make against the target creature, which continues to be a weapon attack.

Answer 2

Generally speaking, a weapon attack has to be made with a weapon. Booming blade (SCAG, p. 142), I will note, does not call for a melee spell attack. It calls for a weapon attack as part of the spell.