Re: [PATCH] use strbuf_addstr() for adding constant strings to a strbuf, part 2

["René Scharfe" <l.s.r@web.de>]

Am 15.09.2016 um 23:39 schrieb Junio C Hamano:
> René Scharfe <l.s.r@web.de> writes:
> 
>> Am 15.09.2016 um 22:01 schrieb Junio C Hamano:
>>> René Scharfe <l.s.r@web.de> writes:
>>>
>>>> Take this for example:
>>>>
>>>> -			strbuf_addf(&o->obuf, _("(bad commit)\n"));
>>>> +			strbuf_addstr(&o->obuf, _("(bad commit)\n"));
>>>>
>>>> If there's a language that uses percent signs instead of parens or as
>>>> regular letters, then they need to be escaped in the translated string
>>>> before, but not after the patch.  As I wrote: silly.
>>>
>>> Ahh, OK, so "This use of addf only has format part and nothing else,
>>> hence the format part can be taken as-is" which is the Coccinelle rule
>>> used to produce this patch is incomplete and always needs manual
>>> inspection, in case the format part wanted to give a literal % in
>>> the output.  E.g. it is a bug to convert this
>>>
>>> 	strbuf_addf(&buf, _("this is 100%% wrong!"));
>>>
>>> to
>>>
>>> 	strbuf_addstr(&buf, _("this is 100%% wrong!"));
>>
>> Right.  Such strings seem to be quite rare in practice, though. 
>>
>>> Thanks for clarification.  Perhaps the strbuf.cocci rule file can
>>> have some comment to warn the person who builds *.patch file to look
>>> for % in E2, or something?
>>
>> Something like this?
> 
> Yup, with something like that I would understdood where that
> puzzling question came from.

Here's something better than a comment:

-- >8 --
Subject: [PATCH] coccicheck: make transformation for strbuf_addf(sb, "...") more precise

We can replace strbuf_addf() calls that just add a simple string with
calls to strbuf_addstr() to make the intent clearer.  We need to be
careful if that string contains printf format specifications like %%,
though, as a simple replacement would change the output.

Add checks to the semantic patch to make sure we only perform the
transformation if the second argument is a string constant (possibly
translated) that doesn't contain any percent signs.

Signed-off-by: Rene Scharfe <l.s.r@web.de>
---
 contrib/coccinelle/strbuf.cocci | 29 ++++++++++++++++++++++++++---
 1 file changed, 26 insertions(+), 3 deletions(-)

diff --git a/contrib/coccinelle/strbuf.cocci b/contrib/coccinelle/strbuf.cocci
index 1e24298..63995f2 100644
--- a/contrib/coccinelle/strbuf.cocci
+++ b/contrib/coccinelle/strbuf.cocci
@@ -1,8 +1,31 @@
+@ strbuf_addf_with_format_only @
+expression E;
+constant fmt;
 @@
-expression E1, E2;
+  strbuf_addf(E,
+(
+  fmt
+|
+  _(fmt)
+)
+  );
+
+@ script:python @
+fmt << strbuf_addf_with_format_only.fmt;
 @@
-- strbuf_addf(E1, E2);
-+ strbuf_addstr(E1, E2);
+cocci.include_match("%" not in fmt)
+
+@ extends strbuf_addf_with_format_only @
+@@
+- strbuf_addf
++ strbuf_addstr
+  (E,
+(
+  fmt
+|
+  _(fmt)
+)
+  );
 
 @@
 expression E1, E2;
-- 
2.10.0