linux-kernel - Re: [PATCH v2] scripts: checkpatch: Check multiple blank lines when deleting code

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Date:   Tue, 05 Mar 2019 15:17:17 -0800
From:   Joe Perches <joe@...ches.com>
To:     Alexandre Ghiti <alex@...ti.fr>,
        Andy Whitcroft <apw@...onical.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] scripts: checkpatch: Check multiple blank lines when
 deleting code

On Tue, 2019-03-05 at 02:12 -0500, Alexandre Ghiti wrote:
> By matching only current line starting with '+', we miss the case
> when deleting code makes consecutive blank lines appear: this patch
> then makes it possible to detect this case by also matching current
> line starting with ' ', which is an already existing blank line.
[]
> diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
[]
> @@ -2081,10 +2081,15 @@ sub fix_inserted_deleted_lines {
>  		}
>  
>  		while (defined($inserted) && ${$inserted}{'LINENR'} == $old_linenr) {
> +			my $len = 1;
>  			push(@lines, ${$inserted}{'LINE'});
> +			# Do not increment the length when inserting a deletion line.
> +			if (${$inserted}{'LINE'} =~ /^\-/) {
> +				$len = 0;
> +			}
>  			$inserted = @{$insertedRef}[$next_insert++];
>  			$new_linenr++;
> -			fixup_current_range(\$lines[$range_last_linenr], $delta_offset++, 1);
> +			fixup_current_range(\$lines[$range_last_linenr], $delta_offset++, $len);

I think this is confusing and unnecessary.
Using --fix can not delete context lines from a patch.

>  		}
>  
>  		if ($save_line) {
> @@ -3298,12 +3303,18 @@ sub process {
>  
>  # check for multiple consecutive blank lines
>  		if ($prevline =~ /^[\+ ]\s*$/ &&
> -		    $line =~ /^\+\s*$/ &&
> +		    $line =~ /^[\+ ]\s*$/ &&
>  		    $last_blank_line != ($linenr - 1)) {
>  			if (CHK("LINE_SPACING",
>  				"Please don't use multiple blank lines\n" . $hereprev) &&
>  			    $fix) {

It's simpler to add a check that $line starts /^\+/ before $fix

Maybe it'd be better to have a separate test for this to make
the output message clearer too.

Something like
	"Avoid deleting lines that create consecutive blank lines"

>  				fix_delete_line($fixlinenr, $rawline);
> +				if ($line =~ /^ \s*$/) {
> +					# If the line is not an inserted blank line, the multiple
> +					# consecutive blank lines are caused by deletion: fix this
> +					# by replacing the blank line with a deletion line.
> +					fix_insert_line($fixlinenr, "\-");
> +				}
>  			}
>  
>  			$last_blank_line = $linenr;