Re: [Linux-kernel-mentees] [PATCH v6] checkpatch: add fix and improve warning msg for non-standard signature

[Joe Perches <joe@perches.com>]

On Sun, 2020-11-29 at 02:13 +0530, Aditya Srivastava wrote:
> Currently checkpatch warns for BAD_SIGN_OFF on non-standard signature
> styles.

Thanks.

Acked-by: Joe Perches <joe@perches.com>

> A large number of these warnings occur because of typo mistakes in
> signature tags. An evaluation over v4.13..v5.8 showed that out of 539
> warnings due to non-standard signatures, 87 are due to typo mistakes.
> 
> Following are the standard signature tags which are often incorrectly
> used, along with their individual counts of incorrect use (over
> v4.13..v5.8):
> 
>  Reviewed-by: 42
>  Signed-off-by: 25
>  Reported-by: 6
>  Acked-by: 4
>  Tested-by: 4
>  Suggested-by: 4
> 
> Provide a fix by calculating levenshtein distance for the signature tag
> with all the standard signatures and suggest a fix with a signature, whose
> edit distance is less than or equal to 2 with the misspelled signature.
> 
> Out of the 86 mispelled signatures fixed with this approach, 85 were
> found to be good corrections and 1 was bad correction.
> 
> Following was found to be a bad correction:
>  Tweeted-by (count: 1) => Tested-by
> 
> Signed-off-by: Aditya Srivastava <yashsri421@gmail.com>
> ---
> applies on next-20201120
> 
> changes in v2: modify commit message: replace specific example with overall evaluation, minor changes
> 
> changes in v3: summarize commit message
> 
> changes in v4: improve commit message; remove signature suggestions of small length (ie 'cc' and 'to')
> 
> changes in v5: modify coding styles: improve function names, whitespaces
> 
> changes in v6: Simplify foreach loop; change standard signature tag values to normal ucfirst; modify warning message
> 
>  scripts/checkpatch.pl | 71 +++++++++++++++++++++++++++++++++++++++++--
>  1 file changed, 69 insertions(+), 2 deletions(-)
> 
> diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
> index fdfd5ec09be6..4a026926139f 100755
> --- a/scripts/checkpatch.pl
> +++ b/scripts/checkpatch.pl
> @@ -506,6 +506,64 @@ our $signature_tags = qr{(?xi:
>  	Cc:
>  )};
>  
> 
> +sub edit_distance_min {
> +	my (@arr) = @_;
> +	my $len = scalar @arr;
> +	if ((scalar @arr) < 1) {
> +		# if underflow, return
> +		return;
> +	}
> +	my $min = $arr[0];
> +	for my $i (0 .. ($len-1)) {
> +		if ($arr[$i] < $min) {
> +			$min = $arr[$i];
> +		}
> +	}
> +	return $min;
> +}
> +
> +sub get_edit_distance {
> +	my ($str1, $str2) = @_;
> +	$str1 = lc($str1);
> +	$str2 = lc($str2);
> +	$str1 =~ s/-//g;
> +	$str2 =~ s/-//g;
> +	my $len1 = length($str1);
> +	my $len2 = length($str2);
> +	# two dimensional array storing minimum edit distance
> +	my @distance;
> +	for my $i (0 .. $len1) {
> +		for my $j (0 .. $len2) {
> +			if ($i == 0) {
> +				$distance[$i][$j] = $j;
> +			} elsif ($j == 0) {
> +				$distance[$i][$j] = $i;
> +			} elsif (substr($str1, $i-1, 1) eq substr($str2, $j-1, 1)) {
> +				$distance[$i][$j] = $distance[$i - 1][$j - 1];
> +			} else {
> +				my $dist1 = $distance[$i][$j - 1]; #insert distance
> +				my $dist2 = $distance[$i - 1][$j]; # remove
> +				my $dist3 = $distance[$i - 1][$j - 1]; #replace
> +				$distance[$i][$j] = 1 + edit_distance_min($dist1, $dist2, $dist3);
> +			}
> +		}
> +	}
> +	return $distance[$len1][$len2];
> +}
> +
> +sub find_standard_signature {
> +	my ($sign_off) = @_;
> +	my @standard_signature_tags = (
> +		'Signed-off-by:', 'Co-developed-by:', 'Acked-by:', 'Tested-by:',
> +		'Reviewed-by:', 'Reported-by:', 'Suggested-by:'
> +	);
> +	foreach my $signature (@standard_signature_tags) {
> +		return $signature if (get_edit_distance($sign_off, $signature) <= 2);
> +	}
> +
> +	return "";
> +}
> +
>  our @typeListMisordered = (
>  	qr{char\s+(?:un)?signed},
>  	qr{int\s+(?:(?:un)?signed\s+)?short\s},
> @@ -2773,8 +2831,17 @@ sub process {
>  			my $ucfirst_sign_off = ucfirst(lc($sign_off));
>  
> 
>  			if ($sign_off !~ /$signature_tags/) {
> -				WARN("BAD_SIGN_OFF",
> -				     "Non-standard signature: $sign_off\n" . $herecurr);
> +				my $suggested_signature = find_standard_signature($sign_off);
> +				if ($suggested_signature eq "") {
> +					WARN("BAD_SIGN_OFF",
> +					     "Non-standard signature: $sign_off\n" . $herecurr);
> +				} else {
> +					if (WARN("BAD_SIGN_OFF",
> +						 "Non-standard signature: '$sign_off' - perhaps '$suggested_signature'?\n" . $herecurr) &&
> +					    $fix) {
> +						$fixed[$fixlinenr] =~ s/$sign_off/$suggested_signature/;
> +					}
> +				}
>  			}
>  			if (defined $space_before && $space_before ne "") {
>  				if (WARN("BAD_SIGN_OFF",


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