Subject: Re: [PATCH v2 3/4] sideband: append suffix for message whose CR in next pktline

From: Junio C Hamano <[email-masked]>
Date: Mon, 14 Jun 2021 12:50:10 +0900

Jiang Xin <[email-masked]> writes:

> From: Jiang Xin <[email-masked]>
>
> When calling "demultiplex_sideband" on a sideband-2 message, will try to
> split the message by line breaks, and append a suffix to each nonempty
> line to clear the end of the screen line.

Subject of "will try" and "append" is missing.  Do you mean that
the helper function in question does these two things?  I.e.

	demultiplex_sideband() used on a sideband #2 will try
	to... and appends ...

> But in the following example,
> there will be no suffix (8 spaces) for "<message-3>":
>
>     PKT-LINE(\2 <message-1> CR <message-2> CR <message-3>)
>     PKT-LINE(\2 CR <message-4> CR <message-5> CR)

That description may mechanically correct, but

   after <message-3>, we fail to clear to the end of line

may make it easier to understand what the problem we are trying to
solve for those who do not remember what these suffix games are
about.

> This is because the line break of "<message-3>" is placed in the next
> pktline message.
>
> Without this fix, t5411 must remove trailing spaces of the actual output
> of "git-push" command before comparing.
>
> Signed-off-by: Jiang Xin <[email-masked]>
> ---
>  sideband.c | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/sideband.c b/sideband.c
> index 6f9e026732..abf2be98e1 100644
> --- a/sideband.c
> +++ b/sideband.c
> @@ -185,6 +185,10 @@ int demultiplex_sideband(const char *me, int status,
>  
>  			if (!scratch->len)
>  				strbuf_addstr(scratch, DISPLAY_PREFIX);
> +			else if (!linelen)
> +				/* buf has a leading CR which ends the remaining
> +				 * scratch of last round of "demultiplex_sideband" */
> +				strbuf_addstr(scratch, suffix);

The style of multi-line comment needs fixing, but the contents of
the comment is a bit hard to grok.

>  			if (linelen > 0) {
>  				maybe_colorize_sideband(scratch, b, linelen);
>  				strbuf_addstr(scratch, suffix);

I wonder if the following is simpler to read, though.

-- >8 --
Subject: [PATCH] sideband: don't lose clear-to-eol at packet boundary

When demultiplex_sideband() sees a CR or LF on the sideband #2, it
adds "suffix" string to clear to the end of the current line, which
helps when relaying a progress display whose records are terminated
with CRs.

The code however forgot that depending on the length of the payload
line, such a CR may fall exactly at the packet boundary and the
number of bytes before the CR from the beginning of the packet could
be zero.  In such a case, the message that was terminated by the CR
were leftover in the "scratch" buffer in the previous call to the
function and we still need to clear to the end of the current line.

Just remove the unnecessary check on linelen; maybe_colorize_sideband()
on 0-byte payload turns into a no-op, and we should be adding clear-to-eol
for each and every CR/LF anyway.

 sideband.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git c/sideband.c w/sideband.c
index 6f9e026732..1575bf16dd 100644
--- c/sideband.c
+++ w/sideband.c
@@ -185,10 +185,9 @@ int demultiplex_sideband(const char *me, int status,
 
 			if (!scratch->len)
 				strbuf_addstr(scratch, DISPLAY_PREFIX);
-			if (linelen > 0) {
-				maybe_colorize_sideband(scratch, b, linelen);
-				strbuf_addstr(scratch, suffix);
-			}
+
+			maybe_colorize_sideband(scratch, b, linelen);
+			strbuf_addstr(scratch, suffix);
 
 			strbuf_addch(scratch, *brk);
 			xwrite(2, scratch->buf, scratch->len);