Can Warlocks take feats that require the "Spellcasting Feature"?

Question

In the past we've seen feats that require ("The ability to cast at least one spell"), the War Caster feat (PHB, p.170), is an example of that.

I recently aquired the book "Bigby Presents: Glory of the Giants", and noticed it states "Spellcasting Feature" as a requirement for the "Rune Shaper" feat (page 18). Digging a bit deeper, I then saw this too in Tasha's, where we see it (among others) on the "Eldritch Adept" feat (page 79), which states as prerequisite "Spellcasting or Pact Magic feature". I suspect that the design goal here is to only allow this feat to be taken by "class-based" casters (Bard, Ranger, Eldritch Knight, etc..) instead of characters that happen to get an odd spell through a racial feature (eg. "Drow Magic"), another feat, etc.

However, I find it a bit odd that the Rune Shaper feat does not mention the Warlocks Pact Magic. RAW this probably means that the Warlock cannot take this feat*. Am I correct to think that?

*) Ignoring the fact that you can take the "Rune Carver" background to get this feat. It states that you get the Rune Shaper feat. I assume that when a background gives you a feat, any of the feat's prerequisites are waived in that case, right?

Answer 1

Spellcasting and Pact Magic are distinct features.

As you have observed, the feat Eldritch Adept makes this distinction apparent in its prerequisite:

Spellcasting or Pact Magic feature

“Spellcasting” is the name of the class feature that provides wizards and other casters with the ability to cast spells. However, warlocks have no feature called “Spellcasting”, but they do have a feature called “Pact Magic”. So a warlock cannot take a feat requiring a class feature called “Spellcasting” because they have no such feature.

Answer 2

There are two ways to qualify for the Rune Shaper feat

The Rune Shaper Feat states:

Prerequisite: Spellcasting Feature or Rune Carver Background

This first of all answers your question as to why a Rune Carver can take this feat. It's not because the background talking about the feat enables it, it's because of the feat specifically talking about this particular background being a valid way to qualify for it, even if you aren't any kind of spellcaster.

That being said, your main question is do Warlocks qualify for this and similarly worded feats? For this you need to know:

There are at least four different ways to learn spells

1. Spellcasting. This is the Class feature that teaches Bards, Clerics, Druids, Paladins, Rangers, Sorcerers, Wizards and Artificers as well as Eldritch Knights and Arcane Tricksters how to cast Spells.
2. Pact Magic. This is the Class feature that teaches Warlocks how to cast Spells.
3. Innate Spellcasting. This is a feature that player characters, such as High Elves or Drow can get through their race and some monsters have aswell.
4. Other methods. There are other ways to learn to cast a spell that aren't from your race and don't specify being the Spellcasting or Pact Magic features either. Examples are the Magic Initiate feat and the spells that the Monk of the Four Elements can cast. I am not sure if these might also qualify for being Innate Spellcasting, but I couldn't find anything on that, so I am putting them in their own category for now.

Rune Shaper is not for all spellcasters

As quoted above and also already mentioned by you Rune Shaper does not specify that "The ability to cast at least one spell" or the Pact Magic feature qualify you for it, as is the case for other feats. Rune Shaper is only for characters that either have the Rune Carver Background or the feature explicitely called Spellcasting, which only those classes listed above have. Any other form of learning how to cast spells will not qualify you for this feat.

Why the distinction?

If you are wondering why they chose to exclude Warlocks and Innate Casters from this feat. I would presume it's because it is heavily focused on long rests as the method to restore your uses of this feat's abilites, while Warlocks regain theirs at short or longs rests and then because it specifically mentions being able to use spells slots for the spells you learn through it, which wouldn't make sense for innate casters, who don't have any spell slots.

Answer 3

When reading 5e rules it is a bad idea to say "elsewhere it was more precise, so the difference here is significant". That was not how 5e rules are written or edited. Doing so leads to wonderful interpretations like "when you can see an invisible creature, they still have advantage on attacks and you have disadvantage against them". 5e was meant to be read and written in a conversational style, not a lawbook.

First, "Spellcasting feature or Pact Magic feature" is a lot of extra, redundant text. Dropping it down to only "Spellcasting feature" as shorthand for "has spell slots" makes the text simpler, and is a plausible thing someone would do.

You should then examine the consequences of both interpretations. Is there anything about the feat (in theme or in mechanics) that would interact poorly with pact magic compared to normal Spellcasting?

It provides you with additional spells known which can be cast using spell slots. None of the spells are specifically ones that would be abusive if cast every short rest, and a warlock could get access to them anyhow with a mere 1 level dip.

It does provide you with a once per long rest "slot free casting", but even that doesn't conflict with the pact magic feature.

Thematically, grabbing magic from knowledge of giant's runes is as much in line with a pact magic of a warlock as it is with the intersection of the "Spellcasting feature" classes of druid, cleric, paladin, ranger and wizard.

Looking at the argument by exclusion (which shouldn't be fully ignored!): The "Eldritch Adept" case is also from another book, so we'd expect different editorial standards to have applied; if it was in the same book (another feat in the book) the argument that the excluding was intended and meaningful is a stronger one.

With next to no thematic reason not to, no mechanical or balance issues, and only an argument by exclusion from a single feat published in a different book, I'd argue that Warlocks should be allowed to grab this feat.

But like all things, ask your DM.