Fix handling of code that is annotated with rustfmt::skip.

[scampi]

A rustfmt::skip'ed block is indented although original lines are
returned. In order to resolve this, the leading whitespaces are trimmed
on each line while retaining the layout; this leaves the skipped code
to be indented as necessary by the caller.

Close #3105

[topecongiro]

Hmm, actually I am not sure if rustfmt is allowed to change the indentation of items under rustfmt_skip.
cc @nrc

[scampi]

@topecongiro at first I thought keeping the layout was enough but indeed I realise now there can be situations where even indenting the code with the rest would be unwanted.

Maybe a better fix would be not to change the indentation at all:

• the source tests added in the PR should remain as is, i.e., the skipped methods shouldn't be indented with the rest
• the method from the original issue shouldn't right-shift either

what do you think ?

[otavio]

@scampi, I agree. If something is marked as rustfmt::skip it must be kept unchanged.

[scampi]

@topecongiro @otavio thanks for your input. Just proposing the changes now to know if that is a good direction. The solution I have found is to keep track of skipped lines which allows caller code to act on those accordingly. Those lines are stored as a list of ranges.

In addition to skipped lines, this list could also be used to keep track of lines that could not be formatted and where the original lines were used instead, e.g., the issue #3045.

[nrc]

Hmm, actually I am not sure if rustfmt is allowed to change the indentation of items under rustfmt_skip.

I think we should not change the indentation at all, since it is possible to make the lines overrun the max width. The user can change the indentation manually and then we'll preserve it.

[nrc]

I'm unclear now - is this intended to fit rustfmt::skiped code? And how is that related to macros?

[scampi]

Taking the shuffle_done! macro definition as example, the method push_skipped_with_span is called on simd_shuffle32, which is annotated with rustfmt::skip. Because the formatting is skipped, the original lines, with the leading whitespaces, are returned.

https://github.com/rust-lang-nursery/rustfmt/blob/4789f65041d428a597f91cea9ad90b548b93cb28/src/visitor.rs#L592

That simd_shuffle32 method is within a macro definition, which body is formatted with MacroBranch::rewrite:

https://github.com/rust-lang-nursery/rustfmt/blob/4789f65041d428a597f91cea9ad90b548b93cb28/src/macros.rs#L1326-L1336

The problem occurs at this point: the following piece is indenting the macro's body.

https://github.com/rust-lang-nursery/rustfmt/blob/4789f65041d428a597f91cea9ad90b548b93cb28/src/macros.rs#L1344-L1349

Since the original (skipped) lines were returned, the simd_shuffle32 method is once again indented, therefore right-shifting that method.

[nrc]

Thank you!

[topecongiro]

@scampi My apologies for the late reply. Thank you for your work and updates!

[scampi]

no worries @topecongiro