Providing a Prebuilt Library File

[uulm-janbaudisch]

I am using maturin for building a project that uses UniFFI. I need some more control of how the shared library gets built and would therefore like to just build it outside of maturin and then provide the library file as input. Maturin already uses the library mode of UniFFI so I think this should theoretically be possible. However I can't figure out how. Is this supported by maturin?

[gistrec]

maturin doesn't support this: it always runs cargo build itself and packages whatever that build produces — there's no option to hand it a prebuilt .so (nothing like that exists in the [tool.maturin] config reference: https://www.maturin.rs/config).

Two practical routes:

1. Keep maturin and push your custom build requirements into the cargo build it runs: rustc-args = [...] and config = [...] in [tool.maturin], plus RUSTFLAGS / cargo profiles. This covers most "I need more control over the cdylib build" cases.
2. Build the library your way and skip maturin for packaging: run UniFFI library mode yourself (uniffi-bindgen generate --library path/to/libfoo.so --language python --out-dir src/) and package the generated bindings plus the .so with a generic backend such as hatchling or setuptools, marking the wheel platform-specific.

If neither fits, this is worth a feature request on the maturin tracker.