Re: [Linux-kernel-mentees] [PATCH v4] checkpatch: add new exception to repeated word check

[Joe Perches <joe@perches.com>]

On Sat, 2020-10-17 at 13:21 +0530, Dwaipayan Ray wrote:
> Recently, commit 4f6ad8aa1eac ("checkpatch: move repeated word test")
> moved the repeated word test to check for more file types. But after
> this, if checkpatch.pl is run on MAINTAINERS, it generates several
> new warnings of the type:
> 
> WARNING: Possible repeated word: 'git'
> 
> For example:
> WARNING: Possible repeated word: 'git'
> +T:	git git://git.kernel.org/pub/scm/linux/kernel/git/rw/uml.git
> 
> So, the pattern "git git://..." is a false positive in this case.
> 
> There are several other combinations which may produce a wrong
> warning message, such as "@size size", ":Begin begin", etc.
> 
> Extend repeated word check to compare the characters before and
> after the word matches. If the preceding or succeeding character
> belongs to the exception list, the warning is avoided.

Not true.

This excludes any non-space character before the first word
and excludes space or punctuation after the second word.

This also adds case insensitive word matching.

> diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
[]
> @@ -3052,19 +3052,30 @@ sub process {
>  
>  # check for repeated words separated by a single space
>  		if ($rawline =~ /^\+/ || $in_commit_log) {
> +			pos($rawline) = 1 if (!$in_commit_log);
>  			while ($rawline =~ /\b($word_pattern) (?=($word_pattern))/g) {
>  
>  				my $first = $1;
>  				my $second = $2;
> -
> +				my $start_pos = $-[1];
> +				my $end_pos = $+[2];
>  				if ($first =~ /(?:struct|union|enum)/) {
>  					pos($rawline) += length($first) + length($second) + 1;
>  					next;
>  				}
>  
> -				next if ($first ne $second);
> +				next if (lc($first) ne lc($second));

case-insensitive matching

>  				next if ($first eq 'long');
>  
> +				# check for character before and after the word matches
> +				my $start_char = '';
> +				my $end_char = '';
> +				$start_char = substr($rawline, $start_pos - 1, 1) if ($start_pos > ($in_commit_log? 0 : 1));
> +				$end_char = substr($rawline, $end_pos, 1) if ($end_pos < length($rawline));
> +
> +				next if ($start_char =~ /^\S$/);

non-space

> +				next if ($end_char !~ /^[\.\,\;\?\!\s]?$/);

space or punctuation.

trivia:

I believe using index would be ~50% faster than !~ here
Perhaps more readable too.

				next if (index(" \t.,;?!", $end_char) >= 0);

> +
>  				if (WARN("REPEATED_WORD",
>  					 "Possible repeated word: '$first'\n" . $herecurr) &&
>  				    $fix) {

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