try to run generate in parallel

[dev-ardi]

There are lots of oportunities to parallelize the generating code using something like rayon and it will speed up some builds by a lot!

[badboy]

I'm not against introducing parallelization where it makes sense, but it does add complexity.
I don't think the code generation itself is much of a bottleneck right now. So before we jump onto introducing more complexity in how it's done I'd like to see some measurements that it is indeed "a lot".

[dev-ardi]

In my project it takes 4m, it is a bottleneck for my workflow.

[badboy]

In my project it takes 4m, it is a bottleneck for my workflow.

Honestly that is surprising to me.
Have you looked closer what exactly is slow there?
How big is your API? What languages are you generating it for?

[dev-ardi]

I haven't profiled it, no. I'm generating only for kotlin,

The generated file is 675KB

[badboy]

That's honestly surprising it takes that long and I think there might be other things going.
If this is for a single language I don't see how we can parallelize that with the current architecture.

To note for Glean it's near-instantenous:

❯ time cargo -q uniffi-bindgen generate --no-format glean-core/src/glean.udl --out-dir out --language kotlin
cargo -q uniffi-bindgen generate --no-format glean-core/src/glean.udl  out    0.09s user 0.03s system 31% cpu 0.371 total

resulting in a 424KB Kotlin file.

---

Do those 4 minutes include fully building uniffi-bindgen first?
Are you using UDL or the macro approach?

[dev-ardi]

We're using the macro approach, and I'm not including building uniff-bindgen. I'm also building it as release.

[badboy]

Is your code open-source so we can take a look at that?

[dev-ardi]

It's unfortunately not...

[mhammond]

If time cargo -q uniffi-bindgen generate... takes 4m, it might somehow be the symbol extraction from the library path you are passing, done by goblin?

[dev-ardi]

how can I know what's taking long in the build? Do you have any form of self profiling?

[mhammond]

We don't have any profiling but we've also never seen this take more than a trivial amount of time. You probably need to use a local build with manually added println statements.

What command exactly are you executing?

[dev-ardi]

cargo run \
        --release \
        --package uniffi-bindgen generate \
        --library target/x86_64-linux-android/debug/[my_library].so \
        --language kotlin \
        --config  uniffi/uniffi.toml \
        --out-dir uniffi/android/lib/src/main/java

The measured time of 4m was done after building this.

[oguzkocer]

We were having a similar issue with long build times for Kotlin bindings generation and it turns out ktlint was the cause of it. Passing --no-format decreased the build time from ~10 minutes to under a second.

It'd probably be worth adding a log output for when the binding generation is complete and maybe even mention that the build will now start formatting the code. That way if anyone else has a similar issue, they can quickly identify the cause of it.

[dev-ardi]

This is it!
I don't think that having klint run by default is a good thing.