Compile error in main code when doc-testing a crate that has the same name as a module

[HeroicKatora]

In a crate that has the same name as a top-level module, exporting a name from this module causes rustdoc (and only rustdoc) to error when it is ran.

// Crate name: `this_crate`.
mod this_crate { pub struct Item; }

pub use this_crate::Item;

error[E0659]: `this_crate` is ambiguous

> cargo test --doc
    Finished test [unoptimized + debuginfo] target(s) in 0.00s
   Doc-tests this_crate
error[E0659]: `this_crate` is ambiguous (name vs any other name during import resolution)
 --> /tmp/test_dir/no-alloc/src/lib.rs:7:9
  |
7 | pub use this_crate::Item;
  |         ^^^^^^^^^^ ambiguous name
  |
  = note: `this_crate` could refer to a crate passed with `--extern`
  = help: use `::this_crate` to refer to this crate unambiguously
note: `this_crate` could also refer to the module defined here
 --> /tmp/test_dir/no-alloc/src/lib.rs:1:1
  |
1 | mod this_crate { pub struct Item; }
  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  = help: use `crate::this_crate` to refer to this module unambiguously
error: aborting due to previous error
For more information about this error, try rustc --explain E0659.
running 0 tests
test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out

> echo $?

0

[ollie27]

This should have been fixed recently by #68357. It errors correctly for me using rustdoc 1.42.0-nightly (41f41b235 2020-01-23). Does it still reproduce for you with the latest nightly?

[HeroicKatora]

@ollie27 The latest nightly errors, so I should probably change the title.

You mean the correct behaviour is erroring? I did not realize this. It seems quite surprising to me that the crate itself compiles (cargo build) but then would not succeed in doc tests due to code that is not actually within a doctest.

[ollie27]

Yeah, actually that error does look wrong. cargo seems to pass --extern this_crate=<path to libthis_crate.rlib> to rustdoc --test which rustdoc either needs to ignore or shouldn't be passed at all.

[joshlf]

Chiming in to say that this is affecting us in zerocopy now (though we can probably work around it).

[LGFae]

I have also run into this issue just now.

Is there an easy way of disabling rustdoc when running cargo test?