Recent minor version upgrade of clap breaks building with a wasm target.

[0xForerunner]

Please complete the following tasks

• I have searched the discussions
• I have searched the open and rejected issues

Rust Version

rustc 1.67.0-nightly (b3bc6bf31 2022-11-24)

Clap Version

between 4.0.22 and 4.0.27

Minimal reproducible code

fn main() {}

Steps to reproduce the bug with the above code

just compile to wasm32-unknown-unknown and it breaks. 4.0.22 works as expected, 4.0.27 does not compile.

Actual Behaviour

~/lending-contracts (develop) » cargo update -p clap                                                                                                                                                                                                       ewoolsey@Erics-MacBook-Pro
    Updating crates.io index
    Updating clap v4.0.22 -> v4.0.27
      Adding errno v0.2.8
      Adding errno-dragonfly v0.1.2
      Adding hermit-abi v0.2.6
      Adding io-lifetimes v1.0.2
      Adding is-terminal v0.4.0
      Adding linux-raw-sys v0.1.3
      Adding rustix v0.36.3
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
~/lending-contracts (develop*) » d b                                                                                                                                                                                              ewoolsey@Erics-MacBook-Pro
   Compiling libc v0.2.137
   Compiling io-lifetimes v1.0.2
   Compiling rustix v0.36.3
   Compiling errno v0.2.8
   Compiling neptune-authorization v0.1.0 (/Users/ewoolsey/lending-contracts/packages/neptune-auth)
error[E0583]: file not found for module `sys`
  --> /Users/ewoolsey/.cargo/registry/src/github.com-1ecc6299db9ec823/errno-0.2.8/src/lib.rs:33:1
   |
33 | mod sys;
   | ^^^^^^^^
   |
   = help: to create the module `sys`, create file "/Users/ewoolsey/.cargo/registry/src/github.com-1ecc6299db9ec823/errno-0.2.8/src/sys.rs" or "/Users/ewoolsey/.cargo/registry/src/github.com-1ecc6299db9ec823/errno-0.2.8/src/sys/mod.rs"

error[E0425]: cannot find function `errno` in module `sys`
   --> /Users/ewoolsey/.cargo/registry/src/github.com-1ecc6299db9ec823/errno-0.2.8/src/lib.rs:101:10
    |
101 |     sys::errno()
    |          ^^^^^ not found in `sys`

error[E0425]: cannot find function `set_errno` in module `sys`
   --> /Users/ewoolsey/.cargo/registry/src/github.com-1ecc6299db9ec823/errno-0.2.8/src/lib.rs:106:10
    |
106 |     sys::set_errno(err)
    |          ^^^^^^^^^ not found in `sys`

Some errors have detailed explanations: E0425, E0583.
For more information about an error, try `rustc --explain E0425`.
error: could not compile `errno` due to 3 previous errors
warning: build failed, waiting for other jobs to finish...
process exited unsuccessfully: exit status: 101

Expected Behaviour

Minor version increments should not introduce breaking changes. I'm not sure exactly which version increment causes the issue but it appears to be from the inclusion of errno.

Additional Context

No response

Debug Output

No response

[0xForerunner]

After fiddling a little bit I can confirm that the offender in 4.0.27 specifically. Everything works as expected on 4.0.26.

[0xForerunner]

Might be useful to add a wasm build to you CI workflow to avoid accidental bugs like that.

[epage]

4.0.27 saw us switch from atty to is-terminal, so that is the root cause.

We also do check wasm32-unknown-unknown and wasm32-wasi in CI

• https://github.com/clap-rs/clap/blob/master/.github/workflows/ci.yml#L78
• https://github.com/clap-rs/clap/blob/master/Makefile#L18

This was all done in #4249 and the wams jobs definitely built is-terminal and it worked

• https://github.com/clap-rs/clap/actions/runs/3541494860/jobs/5945830558
• https://github.com/clap-rs/clap/actions/runs/3541494860/jobs/5945830669

So why did this work in CI but not for you?

[0xForerunner]

So why did this work in CI but not for you?

That's a fantastic question. Is there any other information I can give you that might be useful? Unfortunately I'm working on a large not-yet-open-source project otherwise I'd zip my build for you. I'm working on a Mac, although I doubt that's related to the problem.

[johanhelsing]

Seeing the same thing in our project as well.

To reproduce:

git clone https://github.com/johanhelsing/matchbox
cd matchbox/matchbox_demo
cargo check --target wasm32-unknown-unknown
# no errors
cargo update -p clap
cargo check --target wasm32-unknown-unknown
# same error as ewoolsey

[pinkforest]

So why did this work in CI but not for you?

it seems to have picked atty looking at the logs .. ?

Checking atty v0.2.14

EDIT: wasm CI doesn't include color feature which is the feature that brings is-terminal ?

cargo check --features "deprecated derive cargo env unicode string unstable-replace unstable-grouped" --all-targets --workspace

[pinkforest]

Working on rustup default stable -> 1.65.0 w/ associated w32-u-u target installed

So granular dep changes here were:

root@5d44a4311b14:/matchbox/matchbox_demo# cargo update -p clap

    Updating crates.io index
    Updating clap v4.0.18 -> v4.0.27
    Updating clap_derive v4.0.18 -> v4.0.21
      Adding errno v0.2.8
      Adding errno-dragonfly v0.1.2
      Adding hermit-abi v0.2.6
      Adding io-lifetimes v1.0.2
      Adding is-terminal v0.4.0
      Adding linux-raw-sys v0.1.3
      Adding rustix v0.36.3

I can replicate it inside rust default docker w/ add rustup target add wasm32-u-u from scratch

Immediate work/around seems if one disables the color feature by explicitly setting the defaults:

clap = { version = "4.0", default-features = false, features = ["derive", "std", "help", "usage", "error-context", "suggestions"] }

This prevents feature color (default) being included which brings is-terminal dependency that doesn't work with wasm32-u-u

EDIT: Intiially I had a brainfreeze and I had written no-default-features = true which obviously doesn't work ;)

This would need some cfg magic I think in order for the cargo not include these crates that don't work in wasm32-u-u

It's probably quite involved to cfg default features with: target_family = "wasm", target_os = "unknown"

I've also asked @sunfishcode if is-terminal could stub wasm32-u-u: sunfishcode/is-terminal#9

[epage]

EDIT: wasm CI doesn't include color feature which is the feature that brings is-terminal ?

color is a default feature.

If you look in the linked logs, you see that termcolor and is-terminal are being built. I think the question is if we are using the default target or what I thought was an overriding target.

[epage]

Got a reproduction in CI

There are two failures

• io-lifetimes fails to compile with wasm32-unknown-unknown
• The errno issue above for wasi