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OR pattern in match arm makes rustfmt forget comment alignment #6060

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tnull opened this issue Feb 7, 2024 · 1 comment · May be fixed by #6086
Open

OR pattern in match arm makes rustfmt forget comment alignment #6060

tnull opened this issue Feb 7, 2024 · 1 comment · May be fixed by #6086
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a-comments a-matches match arms, patterns, blocks, etc

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@tnull
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tnull commented Feb 7, 2024 •
edited

When reformatting the following example:

let error_code = match err {
	msgs::DecodeError::UnknownVersion => 0x4000 | 1, // unknown realm byte
	msgs::DecodeError::UnknownRequiredFeature|
	msgs::DecodeError::InvalidValue|
	msgs::DecodeError::ShortRead => 0x4000 | 22, // invalid_onion_payload
	_ => 0x2000 | 2, // Should never happen
};

we receive this result:

let error_code = match err {
	msgs::DecodeError::UnknownVersion => 0x4000 | 1, // unknown realm byte
	msgs::DecodeError::UnknownRequiredFeature
	| msgs::DecodeError::InvalidValue
	| msgs::DecodeError::ShortRead => 0x4000 | 22, // invalid_onion_payload
	_ => 0x2000 | 2,                                 // Should never happen
};

Note that the comment at the end of the second match arm is unaligned with the others. For the third match arm rustfmt even introduces many whitespaces to ensure it's aligned with the in the first match arm. However, it seems that rustfmt entirely forgets about this alignment in the second match arm, presumably due to it being an OR pattern

This seems to happen independently from any particular config option or rustfmt version, but currently I'm using

> rustfmt --version
rustfmt 1.7.0-stable (82e1608d 2023-12-21)
@tnull tnull mentioned this issue Feb 7, 2024
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@ytmimi ytmimi added a-comments a-matches match arms, patterns, blocks, etc labels Feb 7, 2024
@ytmimi
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ytmimi commented Feb 7, 2024

Thanks for the report. Yeah, there's something about the OR pattern that's throwing off the alignment. Without the OR pattern things align as you'd expect.

Input:

fn main() {
    let error_code = match err {
        msgs::DecodeError::UnknownVersion => 0x4000 | 1, // unknown realm byte
        msgs::DecodeError::ShortRead => 0x4000 | 22, // invalid_onion_payload
	_ => 0x2000 | 2, // Should never happen
    };
}

Output:

fn main() {
    let error_code = match err {
        msgs::DecodeError::UnknownVersion => 0x4000 | 1, // unknown realm byte
        msgs::DecodeError::ShortRead => 0x4000 | 22,     // invalid_onion_payload
        _ => 0x2000 | 2,                                 // Should never happen
    };
}

@MarcusGrass MarcusGrass linked a pull request Feb 22, 2024 that will close this issue
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Fix match enum OR comment indentation MarcusGrass/rustfmt
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@tnull @ytmimi