build meta wheel does not respect `metadata_directory` per PEP-517 about maturin HOT 2 OPEN

Maturin ignores the metadata_directory argument in build_wheel which makes it hard to "wrap" build backends and adjust metadata.

Is changing the metadata outside of the build backend allowed in PEP 517? My read was that the build backend controls the metadata. The prepare call is meant for resolver who want to get dependency information but don't actually want to perform the (potentially expensive) compilation (we may not select this version due to conflicts in the deps we get). The cited region in the spec means that you can take this shortcut and have the guarantee that you can build a wheel for installation that has the deps that were used in the resolution.

What's your use case for changing the metadata outside of maturin?

from maturin.

We have a monorepo at work.

So use use backend-path and point to a relative module, which in turn turns relative (including parent dirs) file:// URIs into absolute file:// URIs.

If it simplifies the mental model, the same thing could be accomplished by us publishing the module as a package, setting requires to both our package and maturin, then using ours as the backend.

We'll probably also reuse this package to add the "private" classifier automatically.

from maturin.