Re: [PATCH v2] checkpatch: add --json output mode

[Joe Perches <joe@perches.com>]

On Wed, 2026-04-08 at 13:24 -0400, Sasha Levin wrote:

Adding --json seems sensible but some of the
added checkpatch code seems odd to me.

> diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
> @@ -2395,6 +2400,18 @@ sub report {
>  
>  	push(our @report, $output);
>  
> +	if ($json) {
> +		our ($realfile, $realline);

Seems an odd way to check if $realfile/$readline is set

> +		my %issue = (
> +			level => $level,
> +			type => $type,
> +			message => $msg,
> +		);
> +		$issue{file} = $realfile if (defined $realfile && $realfile ne '');
> +		$issue{line} = $realline + 0 if (defined $realline && $realline);

All the uses of + 0 seem unnecessary, but I gather it's for
string/decimal conversions.

> +sub json_print_result {
> +	my ($filename, $total_errors, $total_warnings, $total_checks,
> +	    $total_lines, $issues, $used_types, $ignored_types) = @_;
> +	my %result = (
> +		filename       => $filename,
> +		total_errors   => $total_errors + 0,
> +		total_warnings => $total_warnings + 0,
> +		total_checks   => $total_checks + 0,
> +		total_lines    => $total_lines + 0,
> +		issues         => $issues,
> +	);
> +	$result{used_types} = $used_types if (defined $used_types);
> +	$result{ignored_types} = $ignored_types if (defined $ignored_types);
> +	my $json_encoder = JSON::PP->new->canonical->utf8;

Maybe add JSON pretty too?

> +	print $json_encoder->encode(\%result) . "\n";

Still missing parentheses around print args.
I do know  that not all existing print uses have parentheses.
I just prefer them to be more like C readable.

> +}
> +
>  sub fixup_current_range {
>  	my ($lineRef, $offset, $length) = @_;
>  
> @@ -2690,14 +2724,15 @@ sub process {
>  	my $last_coalesced_string_linenr = -1;
>  
>  	our @report = ();
> +	our @json_issues = ();
>  	our $cnt_lines = 0;
>  	our $cnt_error = 0;
>  	our $cnt_warn = 0;
>  	our $cnt_chk = 0;
>  
>  	# Trace the real file/line as we go.
> -	my $realfile = '';
> -	my $realline = 0;
> +	our $realfile = '';
> +	our $realline = 0;

?

> @@ -7791,18 +7826,27 @@ sub process {
>  	# If we have no input at all, then there is nothing to report on
>  	# so just keep quiet.
>  	if ($#rawlines == -1) {
> +		if ($json) {
> +			json_print_result($filename, 0, 0, 0, 0, []);
> +		}
>  		exit(0);
>  	}
>  
>  	# In mailback mode only produce a report in the negative, for
>  	# things that appear to be patches.
>  	if ($mailback && ($clean == 1 || !$is_patch)) {
> +		if ($json) {
> +			json_print_result($filename, 0, 0, 0, 0, []);
> +		}
>  		exit(0);
>  	}
>  
>  	# This is not a patch, and we are in 'no-patch' mode so
>  	# just keep quiet.
>  	if (!$chk_patch && !$is_patch) {
> +		if ($json) {
> +			json_print_result($filename, 0, 0, 0, 0, []);
> +		}
>  		exit(0);
>  	}


Duplicated code, maybe use a function or consolidate the code?
Something like:

 	if (($#rawlines == -1) ||
			# If we have no input, there's nothing to report
 	    ($mailback && ($clean == 1 || !$is_patch)) ||
			# In mailback mode only produce a report for what seems to be a patch
 	    (!$chk_patch && !$is_patch)) {
			# This is not a patch, and we are in 'no-patch' mode.
		json_print_result($filename, 0, 0, 0, 0, []) if ($json);
 		exit(0);
 	}

>  
> @@ -7850,6 +7894,13 @@ sub process {
>  		}
>  	}
>  
> +	if ($json) {
> +		my @used = sort keys %use_type;
> +		my @ignored = sort keys %ignore_type;
> +		json_print_result($filename, $cnt_error, $cnt_warn,
> +				  $cnt_chk, $cnt_lines, \@json_issues,
> +				  \@used, \@ignored);
> +	} else {
>  	print report_dump();
>  	if ($summary && !($clean == 1 && $quiet == 1)) {
>  		print "$filename " if ($summary_file);
> @@ -7878,8 +7929,9 @@ NOTE: Whitespace errors detected.
>  EOM
>  		}
>  	}
> +	} # end !$json

I quite dislike misleading indentation.

Perhaps it's  unnecessary here and simpler to use an
exit in the new block at line 7850

>  
> -	if ($clean == 0 && $fix &&
> +	if (!$json && $clean == 0 && $fix &&
>  	    ("@rawlines" ne "@fixed" ||
>  	     $#fixed_inserted >= 0 || $#fixed_deleted >= 0)) {
>  		my $newfile = $filename;
> @@ -7918,7 +7970,7 @@ EOM
>  		}
>  	}
>  
> -	if ($quiet == 0) {
> +	if (!$json && $quiet == 0) {
>  		print "\n";
>  		if ($clean == 1) {
>  			print "$vname has no obvious style problems and is ready for submission.\n";
>