Re: [PATCH 1/6] t0021/rot13-filter: refactor packet reading functions

[Christian Couder <christian.couder@gmail.com>]

On Sun, Oct 22, 2017 at 2:58 AM, Junio C Hamano <gitster@pobox.com> wrote:
> Christian Couder <christian.couder@gmail.com> writes:
>
>> To make it possible in a following commit to move packet
>> reading and writing functions into a Packet.pm module,
>> let's refactor these functions, so they don't handle
>> printing debug output and exiting.
>>
>> Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
>> ---
>>  t/t0021/rot13-filter.pl | 12 ++++++++----
>>  1 file changed, 8 insertions(+), 4 deletions(-)
>>
>> diff --git a/t/t0021/rot13-filter.pl b/t/t0021/rot13-filter.pl
>> index ad685d92f8..e4495a52f3 100644
>> --- a/t/t0021/rot13-filter.pl
>> +++ b/t/t0021/rot13-filter.pl
>> @@ -60,8 +60,7 @@ sub packet_bin_read {
>>       my $bytes_read = read STDIN, $buffer, 4;
>>       if ( $bytes_read == 0 ) {
>>               # EOF - Git stopped talking to us!
>> -             print $debug "STOP\n";
>> -             exit();
>> +             return ( -1, "" );
>>       }
>>       elsif ( $bytes_read != 4 ) {
>>               die "invalid packet: '$buffer'";
>> @@ -85,7 +84,7 @@ sub packet_bin_read {
>>
>>  sub packet_txt_read {
>>       my ( $res, $buf ) = packet_bin_read();
>> -     unless ( $buf eq '' or $buf =~ s/\n$// ) {
>> +     unless ( $res == -1 or $buf eq '' or $buf =~ s/\n$// ) {
>>               die "A non-binary line MUST be terminated by an LF.";
>>       }
>>       return ( $res, $buf );
>> @@ -131,7 +130,12 @@ print $debug "init handshake complete\n";
>>  $debug->flush();
>>
>>  while (1) {
>> -     my ( $command ) = packet_txt_read() =~ /^command=(.+)$/;
>> +     my ( $res, $command ) = packet_txt_read();
>> +     if ( $res == -1 ) {
>> +             print $debug "STOP\n";
>> +             exit();
>> +     }
>> +     $command =~ s/^command=//;
>>       print $debug "IN: $command";
>>       $debug->flush();
>
> This was not an issue in the old code which died upon unexpected EOF
> inside the lowest-level helper packet_bin_read(), but now you have
> one call to packet_bin_read() and many calls to packet_txt_read()
> whose return value is not checked for this new condition you are
> allowing packet_bin_read() to return.  This step taken alone is a
> regression---let's see how the remainder of the series updates the
> callers to compensate.

Yeah, in the new version I will send really soon now, I have made a
number of changes to check the return value for the EOF condition.

> I initially thought that it may be more Perl-ish to return undef or
> string instead of returning a 2-element list, but this code needs to
> distinguish three conditions (i.e. a normal string that is 0 or more
> bytes long, a flush, and an EOF), so that is not sufficient.  Perl
> experts on the list still may be able to suggest a better way than
> the current one to do so, but that is outside the scope of this
> refactoring.

Yeah I can't think of a better way either.

Thanks.