asking here before I commit myself to going down a proverbial "rabbit hole": Why is the output of

cargo build

in

src/rust/engine

not used by the

./pants

invocation in the Pants repository? that is,

./pants

will rebuild the Rust code even after

cargo build

has been run successfully. Compiler options or some reason? And where should I look for the difference?

I've seen spurious rebuilds related to PyO3 before, where even running

./cargo build

without code changes will build

pyo3-build-config

(iirc) and downstream packages. I have no solutions... but does that sound familiar? In addition, you may already be aware of this, but

./cargo build

uses a debug build by default, while

./pants

uses a release one.

MODE=debug ./pants ...

changes that.

I've seen spurious rebuilds related to PyO3 before, where even running

./cargo build

without code changes will build

pyo3-build-config

(iirc) and downstream packages. I have no solutions... but does that sound familiar?

I see pyo3 crates rebuild when I make changes to

engine

crate itself

@fast-nail-55400 does this happen when you run

./cargo build

in root, as well as

cargo build

in

src/rust/engine

? There may be some extra magic going on in that

./cargo

script