neither RUSTFLAGS nor RUSTDOCFLAGS passed to rustdoc by "cargo test --doc"

[decathorpe]

We're running cargo test for many Rust crates we package in Fedora Linux to ensure they work in our environment and on all CPU architectures that we support. We define RUSTFLAGS="--cap-lints=warn" (among other things) to avoid crates starting to fail to build due to things like #![deny(warnings)] with newer Rust versions that add new lints.

Passing "--cap-lints=warn" with RUSTFLAGS works fine for normal library code and test code, but it doesn't get applied to rustdoc when it checks / compiles doctests, and this often causes problems because many crates use #![deny(warnings)] for their doctests / example code in doc comments.

I tried defining RUSTDOCFLAGS="--cap-lints=warn" in addition to having this flag already present in RUSTFLAGS, it didn't change the behaviour. I tried adding a build.rustdocflags = "--cap-lints=warn" setting to .cargo/config, and it didn't change anything either.

It appears that cargo test --doc isn't passing either RUSTFLAGS or RUSTDOCFLAGS to rustdoc correctly.

Good test cases might be the rand_core or pyo3 crates, which fail to build doctests with latest Rust stable due to deny(warnings).

---

Originally filed here:
rust-lang/rust#123424

[weihanglo]

If you have this doc comment and run either

• RUSTDOCFLAGS="--cfg mycfg" cargo t --doc, or
• cargo t --doc --config "build.rustdocflags='--cfg mycfg'"

it will fail as expected.

/// ```
/// #[cfg(mycfg)]
/// assert!(false, "--cfg mycfg");
/// ```
pub fn f() {}

Cargo basically passes the user-provided flags as-is to rustc/rustdoc, so I wonder if rustdoc hijacks lint-level flags for something special. Needs some investigations...

[weihanglo]

Found this: rust-lang/rust#67533. So this is a duplicate of that.

[weihanglo]

Close in favor of rust-lang/rust#67533. Thanks for the report.