[Tarantool-patches] [PATCH v2 luajit 16/30] test: adapt PUC Lua test for %q in fmt for LuaJIT

[Igor Munkin]

Sergey,

On 07.04.21, Sergey Kaplun wrote:
> Igor,
> 

<snipped>

> > > > > string.format(): %q reversible.
> > > > > See also https://luajit.org/extensions.html#lua52.
> > > > > 
> > > > > In Lua 5.1 string.format() does not accept string values containing
> > > > > embedded zeros, except as arguments to the '%q' option.
> > > > > In Lua 5.2 '\0' is not handled differently from other
> > > > > control chars in string.format('%q', ...).
> > > > > See commit 7cc981c14067d4b0e774a6bfb0acfc2f5c911f0d
> > > > > (string.format("%q", str) is now fully reversible
> > > > > (from Lua 5.2).).
> > > > 
> > > > Well, I honestly don't understand what is changed in *semantics*. I've
> > > > tried the following command with Lua 5.2, Lua 5.1 and LuaJIT 2.0.5 as an
> > > > interpreter being tested
> > > > | <interp> -e 'print(string.format("%q", "\0"))'
> > > > 
> > > > I understand the semantics of "%q", but was it just a bug in Lua 5.1?
> > > 
> > > A bug with the test for it???
> > 
> > Well, I can remind you the bug with <tonumber> we fixed the last year.
> > There might be no test for it though, but all in all it has not been
> > fixed in Lua 5.1.
> 
> I mean that this behaviour is verificated by the test. When behaviour is
> changed the test is changed too.
> 
> > 
> > > 
> > > > What does "fully reversible" mean in this context?
> > 
> > This question is left unaddressed.
> 
> I don't know what does Mike mean by these.

Then it would be great to describe the changes on your own. I can hardly
split the comment into yours words and ones taked from Lua Reference
manual or git log, but you are writing that "In Lua 5.2 '\0' is not
handled differently from other control chars". Could you please clarify
the difference you are talking about? Or provide the links describing
it? May be some parts from PIL?

> 
> > 
> > > > 
> > > > I understand only the fact the behaviour differs and you reimplemented
> > > > the test assertion according to Lua 5.2 testing suite. That's all.
> > > > 
> > > > I found not a single word regarding this issue in Lua bugs[1] page,
> > > > except invalid handling of \r[2]. Is there any issue/page with a more
> > > 
> > > It looks unrelated to these changes.
> > > 
> > > > verbose explanation what has been changed in 7cc981c?
> > > 
> > > I just read these lines in Lua 5.1 reference manual :):
> > > | This function does not accept string values containing embedded
> > > | zeros, except as arguments to the q option.
> > 
> > So what? This means literally nothing to me... BTW, I can pass such
> > string to the function and it can yield any bullshit the developer
> > wanted to. That's why we decided to comment such places in a clear and
> > verbose way, didn't we?
> 
> Don't get you point here. AFAIU it means that `%q` is the only one
> option that can contain embeded zeros, so it handles it in the special
> way.

My point relates to the fact, nobody except you can understand the
comment near the change. Hence one need to make the similar
investigation you made. Then what is the sense of commenting the changes
in suite?

> 
> > 
> > > 
> > > As for me, it is just new behaviour of Lua 5.2 -- patterns now accept
> > > '\0' as a reqular character (see
> > > 4541243355a299a9b75042d207feb87295872c3a (patterns now accept '\0' as a
> > > regular character) from Lua repository). So, according to commit
> > > 658ea8752b979102627e2fede7b7ddfbb67ba6c9 (no need to handle '\0'
> > > differently from other control chars in format '%q')) from Lua
> > > repository, this behaviour is excess.
> > > 
> > > Also, it is mentioned here [2].
> > 
> > I see nothing regarding this change there.
> 
> I am talking about this part:
> 
> | Character class %z in patterns is deprecated, as now patterns may
> | contain '\0' as a regular character.

Patterns, not options, right?

> 

<snipped>

> > > > [1]: https://www.lua.org/bugs.html#5.1
> > > > [2]: https://www.lua.org/bugs.html#5.1-4
> > > > 
> > > > -- 
> > > > Best regards,
> > > > IM
> > > 
> > > [1]: https://www.lua.org/manual/5.1/manual.html#pdf-string.format
> > > [2]: https://www.lua.org/manual/5.2/manual.html#8.2

<snipped>

> 
> -- 
> Best regards,
> Sergey Kaplun

-- 
Best regards,
IM