add config inline_attribute_width

[rchaser53]

related: #3343

If the line width is width within config width, attribute is inline.
I don't want to change default rustfmt behavior, so config default value is 0.

[scampi]

Thanks for the PR! You need to add a section in the documentation about this new option:

---- test::configuration_snippet_tests stdout ----
thread 'test::configuration_snippet_tests' panicked at 'inline_attribute_width does not have a configuration guide', src/test/mod.rs:908:17

[rchaser53]

Thank you for the review. I fixed it.
I have a problem now.
configuration_snippet_tests is failed, because of version-gate.
What should I do?
Remove version-gate or remove example in Configurations.md?

[scampi]

For the test failure, maybe replace rust with ignore in https://github.com/rust-lang/rustfmt/pull/3409/files#diff-9de0a570da3404ffd4b364ef6a9f8195R2424

[topecongiro]

I think that we do not need the version gate in this case. The purpose of the version gate is to ensure that users using the default format style won't be affected by formatting changes between rustfmt version updates.

[topecongiro]

Could you apply this to the attribute on extern crate as well please?

[rchaser53]

Thank a lot!
I reflected your reviews.

[scampi]

There is a test failing when run with the beta channel

Mismatch at tests/source/issue-3343.rs:1:
 // rustfmt-config: inline_attribute_width.toml
 
-#[cfg(feature = "alloc")] use core::slice;
+#[cfg(feature = "alloc")]
+use core::slice;
 
-#[cfg(feature = "alloc")] use total_len_is::_50__;
+#[cfg(feature = "alloc")]
+use total_len_is::_50__;
 
 #[cfg(feature = "alloc")]
 use total_len_is::_51___;
Mismatch at tests/source/issue-3343.rs:9:
 
-#[cfg(feature = "alloc")] extern crate len_is_50_;
+#[cfg(feature = "alloc")]
+extern crate len_is_50_;
 
 #[cfg(feature = "alloc")]
 extern crate len_is_51__;

[scampi]

can you add a test to see what happens with @topecongiro comment ? #3409 (comment)

[rchaser53]

Thank you for kindness review many times!
I guess this time is OK.

[topecongiro]

@rchaser53 Thank you for your continuous work on this. Other than typos in the documents, this looks good to me.

[rchaser53]

Oops. Thank you. I fixed it.