Re: [PATCH 1/5] ref-filter: support different email formats

[Hariom verma <hariom18599@gmail.com>]

Hi,

On Tue, Jul 28, 2020 at 4:21 AM Junio C Hamano <gitster@pobox.com> wrote:
>
> "Hariom Verma via GitGitGadget" <gitgitgadget@gmail.com> writes:
>
> > From: Hariom Verma <hariom18599@gmail.com>
> >
> > Currently, ref-filter only supports printing email with arrow brackets.
>
> This is the first time I heard the term "arrow bracket".  Aren't
> they more commonly called angle brackets?

Yeah. Sorry about that.

> > Let's add support for two more email options.
> > - trim : print email without arrow brackets.
>
> Why would this be useful?

It might be useful for using the ref-filter's logic in pretty.c
(especially for `--pretty` formats like `%an` and `%cn`)

> > - localpart : prints the part before the @ sign
>
> Meaning I'd get "<gitster" for me?

No, you'll get "gitster".

> Building small pieces of new feature in each patch is good, and
> adding tests to each step is also good.  Why not do the same for
> docs?

Yeah, I agree with you. I should have focused on documentation too.

> > +static struct email_option{
>
> Missing SP.

I'll fix it.

> > +     enum { EO_INVALID, EO_RAW, EO_TRIM, EO_LOCALPART } option;
> > +} email_option;
> > +
> > @@ -1040,10 +1044,26 @@ static const char *copy_email(const char *buf)
> >       const char *eoemail;
> >       if (!email)
> >               return xstrdup("");
> > -     eoemail = strchr(email, '>');
>
> The original code prepares to see NULL from this strchr(); that is
> why it checks eoemail for NULL and returns an empty string---the
> data is broken (i.e. not an address in angle brackets), which this
> code cannot do anything about---in the later part of the code.

I think this commit still takes care of NULL.
After the switch-case statements, code consists of:
```
if (!eoemail)
    return xstrdup("");
```
Which checks eoemail for NULL. And will return empty string if address
is not in angle brackets.
Same applies for local-part too. If '@' is not present in email
address, it will still return empty string.

> > +     switch (email_option.option) {
> > +     case EO_RAW:
> > +             eoemail = strchr(email, '>') + 1;
>
> And this breaks the carefully laid out error handling by the
> original code.  Adding 1 to NULL is quite undefined.

Yeah. I'll take care of it in the next version.

> > +             break;
> > +     case EO_TRIM:
> > +             email++;
> > +             eoemail = strchr(email, '>');
> > +             break;
> > +     case EO_LOCALPART:
> > +             email++;
> > +             eoemail = strchr(email, '@');
>
> The undocumented design here is that you want to return "hariom" for
> "<hariom@gmail.com>", i.e. out of the "trimmed" e-mail, the part
> before the at-sign is returned.
>
> If the data were "<hariom>", you'd still want to return "hariom" no?
> But because you do not check for NULL, you end up returning an empty
> string.

I never heard of email address without '@' symbol. Thats why I
returned empty string.

Will fix that too.

> I think you want to cut at the first '@' or '>', whichever comes
> first.

If email data can be without '@' symbol, then I guess "yes".

> > +             break;
> > +     case EO_INVALID:
> > +     default:
>
> Invalid and unhandled ones are silently ignored and not treated as
> an error?  I would have thought that at least the "default" one
> would be a BUG(), as you covered all the possible values for the
> enum with case arms.  I wouldn't be surprised if seeing EO_INVALID
> is also a BUG(), i.e. the control flow that led to the caller to
> call this function with EO_INVALID in email_option.option is likely
> to be broken.  It's not like you return "" to protect yourself when
> fed a bad data from objects---a bad value in .option can only come
> here if the parser you wrote for "--format=<string>" produced a
> wrong result.

Christian <chriscool@tuxfamily.org> also suggested me the same. Will
fix this too.

BTW, on master "{author,committer,tagger}email:<xyz>" does not print any error.

> > +             return xstrdup("");
> > +     }
> > +
> >       if (!eoemail)
> >               return xstrdup("");
> > -     return xmemdupz(email, eoemail + 1 - email);
> > +     return xmemdupz(email, eoemail - email);
> >  }
> >
> >  static char *copy_subject(const char *buf, unsigned long len)
> > @@ -1113,7 +1133,7 @@ static void grab_person(const char *who, struct atom_value *val, int deref, void
> >                       continue;
> >               if (name[wholen] != 0 &&
> >                   strcmp(name + wholen, "name") &&
> > -                 strcmp(name + wholen, "email") &&
> > +                 !starts_with(name + wholen, "email") &&
> >                   !starts_with(name + wholen, "date"))
> >                       continue;
> >               if (!wholine)
> > @@ -1124,8 +1144,16 @@ static void grab_person(const char *who, struct atom_value *val, int deref, void
> >                       v->s = copy_line(wholine);
> >               else if (!strcmp(name + wholen, "name"))
> >                       v->s = copy_name(wholine);
> > -             else if (!strcmp(name + wholen, "email"))
> > +             else if (starts_with(name + wholen, "email")) {
> > +                     email_option.option = EO_INVALID;
> > +                     if (!strcmp(name + wholen, "email"))
> > +                             email_option.option = EO_RAW;
> > +                     if (!strcmp(name + wholen, "email:trim"))
> > +                             email_option.option = EO_TRIM;
> > +                     if (!strcmp(name + wholen, "email:localpart"))
> > +                             email_option.option = EO_LOCALPART;
>
> The ref-filter formatting language already knows many "colon plus
> modifier" suffix like "refname:short" and "contents:body", but I do
> not think we have ugly repetition like the above code to parse them.
> Perhaps the addition for "email:<whatever>" can benefit from
> studying and mimicking existing practices a bit more?
>

For "email:<whatever>",
even If I parse that <whatever>. I still make comparison something like:
```
if (!modifier)
    email_option.option = EO_RAW;
else if (!strcmp(modifier, "trim"))
    email_option.option = EO_TRIM;
else if (!strcmp(arg, "localpart"))
    email_option.option = EO_LOCALPART;
```

Thanks,
Hariom