Fixes 5729
`parse_attribute` will panic if the first token is not a `#`. To prevent
this we return early instead of trying to parse an invalid attribute.
There are some tests in the rustfmt test suite that are ignored by
default. I believe these tests are ignored because they have caused
issues with the the `rust-lang/rust` test suite.
However, we recently experienced an issue (5395) that would have been
avoided had these tests been running.
With the introduction of the new `#[rustfmt_only_ci_test]` attribute
macro we can run these tests when the `RUSTFMT_CI` environment variable
is set, which will presumably only be set during rustfmts CI runs.
When the environment variable is not set the `#[rustfmt_only_ci_test]`
will be replaced with an `#[ignore]`.
Fixes 5167
When ``a.rs`` and ``a/mod.rs`` are both present we would emit an error
message telling the user that the module couldn't be found. However,
this behavior is misleading because we're dealing with an ambiguous
module path, not a "file not found" error.
Is the file ``a.rs`` or is it ``a/mod.rs``? Rustfmt can't decide, and
the user needs to resolve this ambiguity themselves.
Now, the error message displayed to the user is in line with what they
would see if they went to compile their code with these conflicting
module names.
