bcs: clean deps, reduce CI clean build time

[phlip9]

Changes

• msrv: 1.56 -> 1.61
• bcs: only depend on serde_core

Description

Hey!

I noticed bcs on the critical path of a build.rs script in CI, so I took a pass at fixing that. After some slight refactoring to (1) remove thiserror and (2) use serde_core traits directly, the "1 vCPU in CI" clean build time is down ~5.7x, without many downsides:

Before:

$ cargo tree --edges build,normal
bcs v0.1.6 (/home/phlip9/dev/bcs)
├── serde v1.0.228
│   ├── serde_core v1.0.228
│   └── serde_derive v1.0.228 (proc-macro)
│       ├── proc-macro2 v1.0.106
│       │   └── unicode-ident v1.0.24
│       ├── quote v1.0.45
│       │   └── proc-macro2 v1.0.106 (*)
│       └── syn v2.0.117
│           ├── proc-macro2 v1.0.106 (*)
│           ├── quote v1.0.45 (*)
│           └── unicode-ident v1.0.24
└── thiserror v1.0.69
    └── thiserror-impl v1.0.69 (proc-macro)
        ├── proc-macro2 v1.0.106 (*)
        ├── quote v1.0.45 (*)
        └── syn v2.0.117 (*)

$ rm -rf /tmp/cargo-target && taskset -c 3 cargo build --target-dir /tmp/cargo-target --lib
    Finished dev [unoptimized + debuginfo] target(s) in 7.89s

After:

$ cargo tree --edges build,normal
    Updating crates.io index
bcs v0.1.6 (/home/phlip9/dev/bcs)
└── serde_core v1.0.228

$ rm -rf /tmp/cargo-target && taskset -c 3 cargo build --target-dir /tmp/cargo-target --lib
   Compiling serde_core v1.0.228
   Compiling bcs v0.1.6 (/home/phlip9/dev/bcs)
    Finished dev [unoptimized + debuginfo] target(s) in 1.38s

[citizen-stig]

Would be nice to see it merged, but latest commit on main branch is 3 years ago...

[phlip9]

cc @ma2bd, you guys still using bcs at linera? any chance we could get this merged? thanks!

[ma2bd]

Interesting. How much time was spent in thiserror? That's the one change that I find a little sad.

@bmwill what do you think?

[bmwill]

@phlip9 Its been a while!

Yeah i'd be supportive of a change like this. I think 100% of what we get from thiserror can be rather trivially implemented explicitly (and tools like claude made maintaining that not that much of a lift)

[citizen-stig]

Just to chime in, if you decide to keep thiserror, could we bump it to v2 + default_features=false ?

But Imho what @phlip9 did looks pretty good to me

[phlip9]

here's the cargo build --timings=html graph on main:

# 1-core cargo build w/ timings
$ rm -rf /tmp/cargo-target && taskset -c 1 env RUSTC_BOOTSTRAP=1 cargo build --target-dir /tmp/cargo-target --lib -Z unstable-options --timings=html

$ open /tmp/cargo-target/cargo-timings/cargo-timing-*.html

[phlip9]

Took the liberty of fixing up CI. Unfortunately due to some cargo dependency resolution quirks, I've had to raise the MSRV from 1.56 -> 1.61. In theory 1.56 should work. Unfortunately this entry in serde_core's Cargo.toml seems to confuse Cargo into adding serde_derive into the lock file, which only has a compatible MSRV of 1.61.

[target.'cfg(any())'.dependencies]
serde_derive = { version = "=1.0.220", path = "../serde_derive" }

I've also committed a working Cargo.lock, since letting cargo resolve the latest dependencies doesn't work for either 1.56 (MSRV) or 1.73 (pinned).

The rust-version -aware resolver is also completely useless... so the fixups need to be done manually:

$ cargo +nightly generate-lockfile -Z unstable-options -Z msrv-policy

$ cargo +nightly update getrandom@0.4.2 --precise 0.3.4
$ cargo +nightly update tempfile --precise 3.5.0
$ cargo +nightly update serde_json --precise 1.0.145
$ cargo +nightly update regex --precise 1.7.3
$ cargo +nightly update rayon --precise 1.6.1
$ cargo +nightly update rayon-core --precise 1.10.2
$ cargo +nightly update libc --precise 0.2.163
$ cargo +nightly update proc-macro2@1 --precise 1.0.103
$ cargo +nightly update syn@2 --precise 2.0.56
$ cargo +nightly update syn@2 --precise 2.0.81
$ cargo +nightly update ryu --precise 1.0.20
$ cargo +nightly update quote --precise 1.0.41
$ cargo +nightly update quote@1 --precise 1.0.41
$ cargo +nightly update either@1 --precise 1.13.0
$ cargo +nightly update unicode-ident@1 --precise 1.0.22
$ cargo +nightly update csv@1 --precise 1.3.0
$ cargo +nightly update unicode-width@0.1 --precise 0.1.8
$ cargo +nightly update plotters --precise 0.3.1
$ cargo +nightly update plotters-svg --precise 0.3.1
$ cargo +nightly update plotters-backend --precise 0.3.2
$ cargo +nightly update csv@1 --precise 1.1.6
$ cargo +nightly update csv-core --precise 0.1.10

[ma2bd]

Took the liberty of fixing up CI. Unfortunately due to some cargo dependency resolution quirks, I've had to raise the MSRV from 1.56 -> 1.61. In theory 1.56 should work. Unfortunately this entry in serde_core's Cargo.toml seems to confuse Cargo into adding serde_derive into the lock file, which only has a compatible MSRV of 1.61.

Thanks!

[citizen-stig]

It looks like you guys are getting closer to merge that!

@bmwill is there anything else important left that needs to be addressed?

Would it be possible to publish new version after this is merged?

[ma2bd]

@phlip9 This was published in version bcs 0.2.0