I recently started using clippy. I have VSCode set up to run clippy on save. I assumed this was a good way to run it seeing as it is provided as an option. However I'm finding it runs very slowly so every time I save the file in order to run cargo run, I have to wait for clippy. It is also running even if I have made no changes and just hit save again. For example I just cloned the rust-headless-chrome repo and I am running their wikipedia example. Everytime I hit save clippy runs for about 40 seconds, even if I haven't made any changes. Is this normal or is something wrong with my setup? Does clippy not work incrementally, ie only re-evaluate code that has actually changed?
#Sould clippy run incrementally?
balmy nova
velvet void
that’s surprising, I’ve never had performance issues with Clippy before
is it possible that you’re running other Cargo commands in between that affects RUSTFLAGS or feature flags or something, and that’s causing a rebuild?
Try setting rust-analyzer.cargo.targetDir to true in your config – is Clippy still slow?
balmy nova
Hhmm, well it's good to know that it can be better and is obviously just something wrong with my setup. I tried adding that setting and clippy still runs for about 40 seconds every time I hit save. These are the Rust related settings I have in VSCode's settting.json:
{
"rust-analyzer.cargo.buildScripts.enable": true,
"rust-analyzer.inlayHints.lifetimeElisionHints.enable": "always",
"rust-analyzer.lens.implementations.enable": false,
"rust-analyzer.procMacro.attributes.enable": false,
"rust-analyzer.procMacro.enable": false,
"rust-analyzer.check.command": "clippy",
"rust-analyzer.cargo.targetDir": true,
}
have you checked that those settings are actually beïng applied btw?
just to make sure
And how long does cargo clippy take on the command-line?
balmy nova
I don't know how to check if the settings are being applied. VSCode seems to grey out settings it doesn't recognise/have been deprecated, and it doesn't do that for any of these settings but beyond that I don't know.
I tried cargo clippy and the first time it took about 40 seconds, mostly on this step:
max@max-Latitude-7290:~/projects/rust-headless-chrome$ cargo clippy
Compiling headless_chrome v1.0.15 (/home/max/projects/rust-headless-chrome)
Building [=======================> ] 139/140: headless_chrome
After that it ran instantly, until I tried hitting save again in the editor and then cargo clippy would run slow again once, then quick after.
Seems like the problem the problem is specifically with the rust-headless-chrome repo. I tried saving files without changes in one of my own repos and it does run slow at first at a change but then runs instantly so is obviously successfully caching the work.
I tried setting "rust-analyzer.cargo.buildScripts.enable": false, to see if that would help with the headless_chrome problem but it made no differnce. I think I'll just make a new repo, rather than playing around with their example directly in the rust-headless-chrome repo.
balmy nova
I've copied the example to a new repo and clippy works fine there, so I'm just going to use that instead. Thanks for your help.
inland snow
Clippy (and all the build tools) have a hard time with large projects
median wing
I don't know how to check if the settings are being applied. VSCode seems to gre...
Also, maybe I would suggest you can try using a different linker like mold or lld than the standard ld and see if that speeds things up for you. 🙂
velvet void
that shouldn’t affect Clippy
median wing
that shouldn’t affect Clippy
I think it does like clippy still needs to compile stuff sometimes to do a check like for example I find that when I run clippy with mold it speeds things up quite a lot. 🙂
median wing
Maybe for proc macros I guess?
Yes maybe 🤷 , but I sometimes do find when running clippy like it compiles stuff like the project binary and stuff so maybe a linker could speed that up too. 🙂