Re: [PATCH v2] checkpatch: add double empty line check

[Joe Perches <joe@perches.com>]

On Tue, 2012-11-20 at 11:52 +0000, Andy Whitcroft wrote:
> On Sat, Nov 17, 2012 at 01:17:37PM +0200, Eilon Greenstein wrote:
> > Changes from previous attempt:
> > - Use CHK instead of WARN
> > - Issue only one warning per empty lines block
> > 
> > Signed-off-by: Eilon Greenstein <eilong@broadcom.com>
> > ---
> >  scripts/checkpatch.pl |    8 ++++++++
> >  1 file changed, 8 insertions(+)
> > 
> > diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
> > index 21a9f5d..13d264f 100755
> > --- a/scripts/checkpatch.pl
> > +++ b/scripts/checkpatch.pl
> > @@ -3579,6 +3579,14 @@ sub process {
> >  			WARN("EXPORTED_WORLD_WRITABLE",
> >  			     "Exporting world writable files is usually an error. Consider more restrictive permissions.\n" . $herecurr);
> >  		}
> > +
> > +# check for double empty lines
> > +		if ($line =~ /^\+\s*$/ &&
> > +		    ($rawlines[$linenr] =~ /^\s*$/ ||
> > +		     $prevline =~ /^\+?\s*$/ && $rawlines[$linenr] !~ /^\+\s*$/)) {
> > +			CHK("DOUBLE_EMPTY_LINE",
> > +			    "One empty line should be sufficient. Consider removing this one.\n" . $herecurr);
> > +		}
> >  	}
> >  
> >  	# If we have no input at all, then there is nothing to report on
> 
> In your previous version you indicated you would be emiting one per group
> of lines, I do not see how this does that.  Also this fails if the fragment
> is at the top of the hunk emiting a perl warning.  We should probabally
> use the suppress approach.
> 
> How about something like the below.
> 
> -apw
> 
> 
> >From 848ebffa8656a1ff96a91788ec0f1c04dab9c3e9 Mon Sep 17 00:00:00 2001
> From: Andy Whitcroft <apw@canonical.com>
> Date: Sat, 17 Nov 2012 13:17:37 +0200
> Subject: [PATCH] checkpatch: strict warning for multiple blank lines
> 
> Signed-off-by: Andy Whitcroft <apw@canonical.com>
> ---
>  scripts/checkpatch.pl |   11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
> index f18750e..dbc68f3 100755
> --- a/scripts/checkpatch.pl
> +++ b/scripts/checkpatch.pl
> @@ -1411,6 +1411,7 @@ sub process {
>  	my %suppress_whiletrailers;
>  	my %suppress_export;
>  	my $suppress_statement = 0;
> +	my $suppress_multipleblank = -1;
>  
>  	# Pre-scan the patch sanitizing the lines.
>  	# Pre-scan the patch looking for any __setup documentation.
> @@ -1521,6 +1522,7 @@ sub process {
>  			%suppress_whiletrailers = ();
>  			%suppress_export = ();
>  			$suppress_statement = 0;
> +			$suppress_multipleblank = -1;
>  			next;
>  
>  # track the line number as we move through the hunk, note that
> @@ -1930,6 +1932,15 @@ sub process {
>  			      "use the SSYNC() macro in asm/blackfin.h\n" . $herevet);
>  		}
>  
> +# multiple blank lines.
> +		if ($line =~ /^-/ || ($suppress_multipleblank == $linenr && $line =~ /^[ \+]\s*$/)) {
> +			$suppress_multipleblank++;
> +		} elsif ($prevline =~ /^\+\s*$/ and $line =~ /^\+\s*$/) {
> +			$suppress_multipleblank = $linenr + 1;
> +			CHK("MULTIPLE_EMPTY_LINE",
> +			    "One empty line should be sufficient. Consider removing this one.\n" . $herecurr);
> +		}
> +
>  # Check for potential 'bare' types
>  		my ($stat, $cond, $line_nr_next, $remain_next, $off_next,
>  		    $realline_next);

What about:

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index d2d5ba1..ed4ec9d 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -1382,6 +1382,7 @@ sub process {
 	my $comment_edge = 0;
 	my $first_line = 0;
 	my $p1_prefix = '';
+	my $last_blank_linenr = 0;
 
 	my $prev_values = 'E';
 
@@ -3323,6 +3324,15 @@ sub process {
 			     "sizeof $1 should be sizeof($1)\n" . $herecurr);
 		}
 
+# check for multiple blank lines, warn only on the second one in a block
+		if ($rawline =~ /^.\s*$/ &&
+		    $prevrawline =~ /^.\s*$/ &&
+		    $linenr != $last_blank_linenr + 1) {
+			CHK("DOUBLE_EMPTY_LINE",
+			    "One blank line separating blocks is generally sufficient\n" . $herecurr);
+			$last_blank_linenr = $linenr;
+		}
+
 # check for line continuations in quoted strings with odd counts of "
 		if ($rawline =~ /\\$/ && $rawline =~ tr/"/"/ % 2) {
 			WARN("LINE_CONTINUATIONS",