Rustfmt can't find module if a directory and module is named the same

[Marwes]

Reproduction, clone https://github.com/Marwes/rustfmt-bug and run cargo fmt.

error[E0583]: file not found for module `support`
 --> /home/markus/Code/rustfmt-bug/tests/test.rs:1:5
  |
1 | mod support;
  |     ^^^^^^^
  |
  = help: name the file either test/support.rs or test/support/mod.rs inside the directory "/home/markus/Code/rustfmt-bug/tests"

Since both tests/test.rs and tests/test/ exists, rustfmt is unable to find tests/support/mod.rs as mod support; as it appears that rustfmt thinks that test.rs is part of the tests/test/ module tree. This is different from how rustc/cargo sees it which compile the code happily.

I guess rustc/cargo has different module resolution for tests/ than src/ since rustfmt's behaviour would be correct in src/.

Workaround is to use #[path = "module.rs"] on the offending module.

[rchaser53]

How about this?
cargo fmt -- tests/*/*.rs tests/*.rs

[Marwes]

$ cargo fmt -- tests/*/*.rs tests/*.rs
error[E0583]: file not found for module `support`
 --> \\?\C:\Users\Markus\Dropbox\Programming\rustfmt-bug\tests\test.rs:1:5
  |
1 | mod support;
  |     ^^^^^^^
  |
  = help: name the file either test\support.rs or test\support\mod.rs inside the directory "\\?\C:\Users\Markus\Dropbox\Programming\rustfmt-bug\tests"

error[E0583]: file not found for module `support`
 --> \\?\C:\Users\Markus\Dropbox\Programming\rustfmt-bug\tests\test.rs:1:5
  |
1 | mod support;
  |     ^^^^^^^
  |
  = help: name the file either test\support.rs or test\support\mod.rs inside the directory "\\?\C:\Users\Markus\Dropbox\Programming\rustfmt-bug\tests"

[rchaser53]

Do you use Windows?
cargo fmt -- tests/*/*.rs tests/*.rs works in macOS(10.14.6).
It seems to be a problem that depends on Windows.

[Marwes]

cargo fmt -- tests/*/*.rs tests/*.rs was run on windows but plain cargo fmt breaks on linux as well.

[rchaser53]

I succeeded to reproduce the bug on ubuntu 18.04. Thank you.

[rchaser53]

The rustfmt was in my environment a bit old.
This bug is also happended on the latest rustfmt on macOS.

[topecongiro]

As a workaround, the following command may work if you are using nightly (you also need fd):

rustfmt --unstable-features --skip-children `fd -e rs`

[pnkfelix]

(It would be good if this issue's title included the detail that its specifically about resolution in cargo tests/ directory. At least, that detail was quite relevant to me when I was trying to figure out what was wrong when I encountered it.)

[topecongiro]

This issue will be fixed in 2.0.