wasm-bindgen no longer works with feature resolver version 1

[dtolnay]

$ cargo +stable new repro --edition=2018
$ cd repro
$ cargo +stable add wasm-bindgen@=0.2.96   # =0.2.95 works
$ cargo +stable check
...
error[E0554]: `#![feature]` may not be used on the stable release channel
 --> ~/.cargo/registry/src/index.crates.io-6f17d22bba15001f/wasm-bindgen-macro-0.2.96/src/lib.rs:4:5
  |
4 |     feature(allow_internal_unstable),
  |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
For more information about this error, try `rustc --explain E0554`.
error: could not compile `wasm-bindgen-macro` (lib) due to 1 previous error

$ rustc +stable --version --verbose
rustc 1.83.0 (90b35a623 2024-11-26)
binary: rustc
commit-hash: 90b35a6239c3d8bdabc530a6a0816f7ff89a0aaf
commit-date: 2024-11-26
host: x86_64-unknown-linux-gnu
release: 1.83.0
LLVM version: 19.1.1

[dtolnay]

Bisects to 83c9deb (#4284). @daxpedda

[daxpedda]

I added a CI check so this doesn't happen again.
Fixed in #4306.

[daxpedda]

So I had to dig into this a bit more, because apparently no [target.'cfg(...)'.dependencies] table worked correctly unless specifying the target. So that means no target_feature and no cfg flag. I found out that the issue can be solved by just using resolver = "2".

While I was working in #4306 to fix this issue without requiring resolver = "2", there are some interactions that can't be easily addressed and overall it makes the situation much worse. So I'm tending towards just requiring resolver = "2".

Any input would be appreciated!

[mxsrm]

You are breaking a lot of crates that depend on things like chrono (which depend on you), if the crates are using resolver version 1. Please revert the changes and publish a new hotfixed version that does not break ecosystemwide crates?

v0.2.97 is still affected:

❯ cargo build --release
warning: no edition set: defaulting to the 2015 edition while the latest is 2021
   Compiling wasm-bindgen-shared v0.2.97
   Compiling log v0.4.22
   Compiling bumpalo v3.16.0
   Compiling wasm-bindgen v0.2.97
   Compiling rav1e v0.7.1
   Compiling syn v2.0.90
   Compiling getrandom v0.2.15
   Compiling wasm-bindgen-backend v0.2.97
   Compiling thiserror-impl v1.0.69
   Compiling serde_derive v1.0.215
   Compiling profiling-procmacros v1.0.16
   Compiling arg_enum_proc_macro v0.3.4
   Compiling num-derive v0.4.2
   Compiling zerocopy-derive v0.7.35
   Compiling thiserror-impl v2.0.3
   Compiling displaydoc v0.2.5
   Compiling wasm-bindgen-macro-support v0.2.97
   Compiling profiling v1.0.16
   Compiling zerocopy v0.7.35
   Compiling thiserror v1.0.69
   Compiling pest v2.7.14
   Compiling wasm-bindgen-macro v0.2.97
error[E0554]: `#![feature]` may not be used on the stable release channel
 --> /home/max/.cargo/registry/src/index.crates.io-6f17d22bba15001f/wasm-bindgen-macro-0.2.97/src/lib.rs:4:5
  |
4 |     feature(allow_internal_unstable),
  |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

For more information about this error, try `rustc --explain E0554`.
error: could not compile `wasm-bindgen-macro` (lib) due to 1 previous error
warning: build failed, waiting for other jobs to finish...

[ozabalaferrera]

I'm not sure I fully understand what's going on here, but it seems like this is also the cause for this failed test/build:
https://github.com/cloudevents/sdk-rust/actions/runs/12123953925/job/33800591907
Does that seem right? Any updates on this issue?

[smoelius]

@ozabalaferrera When I change this line to edition = "2021", the problem goes away: https://github.com/cloudevents/sdk-rust/blob/09661ddaf72dfec2133962ae4dc6d322823558a1/Cargo.toml#L6

I think this is why: https://doc.rust-lang.org/edition-guide/rust-2021/default-cargo-resolver.html

[ozabalaferrera]

@smoelius, I don't think that worked for me. I also had tried setting resolver="2". here is the commit and test results: ozabalaferrera/cloudevents-sdk-rust@0972757