Re: bug report: cover letter is inheriting last patch's message ID with send-email

> Hi,
>
> On Wed, May 17, 2023 at 12:22 PM Junio C Hamano <gitster@pobox.com> wrote:
>>
>> Junio C Hamano <gitster@pobox.com> writes:
>>
>> >> # With the attached patches, where all of the patches have a
>> >> # Message-Id but the cover letter doesn't.
>> >> git send-email *.patch
>>
>> I suspect this is a recent regression with the addition of the
>> pre_process_file step.  56adddaa (send-email: refactor header
>> generation functions, 2023-04-19) makes all messages parsed
>> before the first message is sent out, by calling a sub
>> "pre_process_file" before invoking the validate hook.  The same sub
>> is called again for each message when it is sent out, as the
>> processing in that step is shared between the time the message gets
>> vetted and the time the message gets sent.
>>
>> Unfortunately, $message_id variable is assigned to in that sub.  So
>> it is very much understandable why this happens.
>>
>> I wonder if it is just doing something silly like this?
>>
>> --- >8 ---
>> Subject: [PATCH] send-email: clear the $message_id after validation
>>
>> Recently git-send-email started parsing the same message twice, once
>> to validate _all_ the message before sending even the first one, and
>> then after the validation hook is happy and each message gets sent,
>> to read the contents to find out where to send to etc.
>>
>> Unfortunately, the effect of reading the messages for validation
>> lingered even after the validation is done.  Namely $message_id gets
>> assigned if exists in the input files but the variable is global,
>> and it is not cleared before pre_process_file runs.  This causes
>> reading a message without a message-id followed by reading a message
>> with a message-id to misbehave---the sub reports as if the message
>> had the same id as the previously written one.
>>
>> Clear the variable before starting to read the headers in
>> pre_process_file
>>
>> Signed-off-by: Junio C Hamano <gitster@pobox.com>
>> ---
>>
>>  * I am not surprised at all if there are similar problems in this
>>    function around variables other than $message_id; this patch is
>>    merely reacting to the bug report and not systematically hunting
>>    and fixing the bugs coming from the same root cause.  If the
>>    original author of the pre_process_file change is still around,
>>    the second sets of eyes from them is very much appreciated.
>>
>>  git-send-email.perl | 1 +
>>  1 file changed, 1 insertion(+)
>>
>> diff --git c/git-send-email.perl w/git-send-email.perl
>> index 89d8237e89..889ef388c8 100755
>> --- c/git-send-email.perl
>> +++ w/git-send-email.perl
>> @@ -1771,6 +1771,7 @@ sub send_message {
>>  sub pre_process_file {
>>         my ($t, $quiet) = @_;
>>
>> +       undef $message_id;
>>         open my $fh, "<", $t or die sprintf(__("can't open file %s"), $t);
>>
>>         my $author = undef;
>
> I can confirm this fixes the regression for me. Thus:
>
> Tested-by: Douglas Anderson <dianders@chromium.org>