rustdoc: Building docs for tokio panics

[davidpdrsn]

Building the docs in the root of tokio panics with this message:

❯ RUSTDOCFLAGS="--cfg docsrs" cargo +nightly doc --all-features
thread 'main' panicked at 'no entry found for key', src/tools/cargo/src/cargo/ops/cargo_compile.rs:1638:21
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

If you go into one of the subdirectories it works:

~/dev/tokio
❯ cd tokio

~/dev/tokio/tokio
❯ RUSTDOCFLAGS="--cfg docsrs" cargo +nightly doc --all-features
    Finished dev [unoptimized + debuginfo] target(s) in 0.12s

Feels like a bug in rustdoc.

Meta

rustup show:

Default host: x86_64-apple-darwin
rustup home:  /Users/david.pedersen/.rustup

installed toolchains
--------------------

stable-x86_64-apple-darwin
beta-x86_64-apple-darwin
nightly-2020-10-11-x86_64-apple-darwin
nightly-2020-12-28-x86_64-apple-darwin
nightly-2021-03-04-x86_64-apple-darwin
nightly-x86_64-apple-darwin
1.47.0-x86_64-apple-darwin
1.49.0-x86_64-apple-darwin
1.50.0-x86_64-apple-darwin

active toolchain
----------------

nightly-x86_64-apple-darwin (directory override for '...')
rustc 1.52.0-nightly (107896c32 2021-03-15)

Backtrace

❯ RUST_BACKTRACE=1 RUSTDOCFLAGS="--cfg docsrs" cargo +nightly doc --all-features
thread 'main' panicked at 'no entry found for key', src/tools/cargo/src/cargo/ops/cargo_compile.rs:1638:21
stack backtrace:
   0: _rust_begin_unwind
   1: core::panicking::panic_fmt
   2: core::option::expect_failed
   3: cargo::ops::cargo_compile::remove_duplicate_doc::visit
   4: cargo::ops::cargo_compile::create_bcx
   5: cargo::ops::cargo_compile::compile_ws
   6: cargo::ops::cargo_compile::compile
   7: cargo::ops::cargo_doc::doc
   8: cargo::commands::doc::exec
   9: cargo::cli::main
  10: cargo::main
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

cc @Darksonn

[Darksonn]

To be clear, Tokio uses the workspace feature. It panics if you run it in the workspace folder, but not in any of the individual crates.

[jonas-schievink]

Looks like Cargo panics, so this should be reported at https://github.com/rust-lang/cargo

[davidpdrsn]

Filed rust-lang/cargo#9274