All the git variants of Plasma packages on the AUR depend on the git variants of dependencies
plasma-desktop-git may depend on this package

The keyword here is may. It means this is a possible dependency path, not something that is guaranteed to always occur. That's theory.

But, in practice, kdeconnect-git does depend on it, and this leads to plasma-bigscreen-git failing to compile because pacman attempts to replace this package with the non-git version. If that replacement is accepted, the rest of a plasma-git setup breaks due to incompatible builds being mixed, and leads to an unbootable Plasma session.

For anyone running Plasma from git for development or testing, this currently means having to manually patch this PKGBUILD to add a provides entry so that dependency resolution works correctly. That is, provides=(qqc2-desktop-style) means that it provides what the original package does and so pacman won't break the setup by trying to hard-push the two together and not being able to do so.

That provides line is already how the other Plasma git packages are handled (for example, see kdeconnect-git on the AUR), and this package is currently the only outlier in that regard. This is the only one that doesn't offer itself as a provider of what the non-git version also provides.

Adding it avoids pacman trying to replace this package and prevents a single AUR update from breaking an otherwise consistent plasma-git installation as soon as one logs out from the Plasma session.

I will not be doing that. All the git variants of Plasma packages on the AUR depend on the git variants of dependencies, e.g. plasma-desktop-git may depend on this package. There is no need for the provides field.

Thank you, but it seems like you forgot to add the provides line.

Without it, compiling Plasma from master git fails because it wants to replace this package with the original qqc2-desktop-style. So please add it so this package finally stops conflicting.

Please add as well:

conflicts=('qqc2-desktop-style')
provides=('qqc2-desktop-style')

So it stops conflicting with the original package.

Again, please unhardcode that qqc2-desktop-style name as it causes it to fail building.

Please replace:

cd "qqc2-desktop-style"

with

cd "${pkgname%-git}"

and:

  cmake -B build -S $_pkgname \

with:

  cmake -B build -S "${pkgname%-git}" \

so it stops to fail building and actually builds successfully.

In pkgver(), replace cd "$pkgname" with cd "${pkgname%-git}", otherwise it fails to build