Re: [RFC 3/4] ref-filter: change parsing function error handling

[Оля Тележная]

2018-03-13 22:18 GMT+03:00 Martin Ågren :
> On 13 March 2018 at 11:16, Olga Telezhnaya  wrote:
>> Continue removing any printing from ref-filter formatting logic,
>> so that it could be more general.
>>
>> Change the signature of parse_ref_filter_atom() by changing return value,
>> adding previous return value to function parameter and also adding
>> strbuf parameter for error message.
>
> I think the current return value is always non-negative. Maybe it would
> be easier to leave the return value as-is, except return negative on
> error? Unless I am missing something?

That's interesting. I like your idea, but let's see what other people think.
If others agree with us, I am ready to implement your solution.

>
>>
>> Signed-off-by: Olga Telezhnaia 
>> ---
>>  ref-filter.c | 45 -
>>  1 file changed, 32 insertions(+), 13 deletions(-)
>>
>> diff --git a/ref-filter.c b/ref-filter.c
>> index 07bedc636398c..e146215bf1e64 100644
>> --- a/ref-filter.c
>> +++ b/ref-filter.c
>> @@ -397,7 +397,8 @@ struct atom_value {
>>   * Used to parse format string and sort specifiers
>>   */
>>  static int parse_ref_filter_atom(const struct ref_format *format,
>> -const char *atom, const char *ep)
>> +const char *atom, const char *ep, int *res,
>> +struct strbuf *err)
>>  {
>> const char *sp;
>> const char *arg;
>> @@ -406,14 +407,18 @@ static int parse_ref_filter_atom(const struct 
>> ref_format *format,
>> sp = atom;
>> if (*sp == '*' && sp < ep)
>> sp++; /* deref */
>> -   if (ep <= sp)
>> -   die(_("malformed field name: %.*s"), (int)(ep-atom), atom);
>> +   if (ep <= sp) {
>> +   strbuf_addf(err, _("malformed field name: %.*s"), 
>> (int)(ep-atom), atom);
>> +   return -1;
>> +   }
>>
>> /* Do we have the atom already used elsewhere? */
>> for (i = 0; i < used_atom_cnt; i++) {
>> int len = strlen(used_atom[i].name);
>> -   if (len == ep - atom && !memcmp(used_atom[i].name, atom, 
>> len))
>> -   return i;
>> +   if (len == ep - atom && !memcmp(used_atom[i].name, atom, 
>> len)) {
>> +   *res = i;
>> +   return 0;
>> +   }
>> }
>
> If you did so, this hunk above would not need to be changed ...
>
>> @@ -458,7 +465,8 @@ static int parse_ref_filter_atom(const struct ref_format 
>> *format,
>> need_tagged = 1;
>> if (!strcmp(valid_atom[i].name, "symref"))
>> need_symref = 1;
>> -   return at;
>> +   *res = at;
>> +   return 0;
>>  }
>
> ... nor this one above ...
>
>> if (!ep)
>> return error(_("malformed format string %s"), sp);
>> /* sp points at "%(" and ep points at the closing ")" */
>> -   at = parse_ref_filter_atom(format, sp + 2, ep);
>> +   if (parse_ref_filter_atom(format, sp + 2, ep, , ))
>> +   die("%s", err.buf);
>
> And this would be more like "if (at < 0) die(...)".
>
>> for (cp = format->format; *cp && (sp = find_next(cp)); cp = ep + 1) {
>> struct atom_value *atomv;
>> +   struct strbuf err = STRBUF_INIT;
>> +   int pos;
>>
>> ep = strchr(sp, ')');
>> if (cp < sp)
>> append_literal(cp, sp, );
>> -   get_ref_atom_value(info,
>> -  parse_ref_filter_atom(format, sp + 2, ep),
>> -  );
>> +   if (parse_ref_filter_atom(format, sp + 2, ep, , ))
>> +   return -1;
>> +   get_ref_atom_value(info, pos, );
>> if (atomv->handler(atomv, , error_buf))
>> return -1;
>> +   strbuf_release();
>
> This looks leaky: if we get an error, we've got something in the buffer
> but we do not release it because we return early. Stepping back a bit, I
> wonder why we do not do anything at all with "err". Stepping back a bit
> more :-) I wonder if you could get rid of "err" and pass "error_buf" to
> parse_ref_filter_atom() instead. Our caller would like to have access to
> the error string?

Fully agree, I don't know why I decided to create one more buffer. Fixed.

>
> This ties back to my comment on the first patch -- "return negative if
> and only if you add some error string to the buffer" might be a useful
> rule?
>
> Martin

Re: [RFC 3/4] ref-filter: change parsing function error handling

[Martin Ågren]

On 13 March 2018 at 11:16, Olga Telezhnaya  wrote:
> Continue removing any printing from ref-filter formatting logic,
> so that it could be more general.
>
> Change the signature of parse_ref_filter_atom() by changing return value,
> adding previous return value to function parameter and also adding
> strbuf parameter for error message.

I think the current return value is always non-negative. Maybe it would
be easier to leave the return value as-is, except return negative on
error? Unless I am missing something?

>
> Signed-off-by: Olga Telezhnaia 
> ---
>  ref-filter.c | 45 -
>  1 file changed, 32 insertions(+), 13 deletions(-)
>
> diff --git a/ref-filter.c b/ref-filter.c
> index 07bedc636398c..e146215bf1e64 100644
> --- a/ref-filter.c
> +++ b/ref-filter.c
> @@ -397,7 +397,8 @@ struct atom_value {
>   * Used to parse format string and sort specifiers
>   */
>  static int parse_ref_filter_atom(const struct ref_format *format,
> -const char *atom, const char *ep)
> +const char *atom, const char *ep, int *res,
> +struct strbuf *err)
>  {
> const char *sp;
> const char *arg;
> @@ -406,14 +407,18 @@ static int parse_ref_filter_atom(const struct 
> ref_format *format,
> sp = atom;
> if (*sp == '*' && sp < ep)
> sp++; /* deref */
> -   if (ep <= sp)
> -   die(_("malformed field name: %.*s"), (int)(ep-atom), atom);
> +   if (ep <= sp) {
> +   strbuf_addf(err, _("malformed field name: %.*s"), 
> (int)(ep-atom), atom);
> +   return -1;
> +   }
>
> /* Do we have the atom already used elsewhere? */
> for (i = 0; i < used_atom_cnt; i++) {
> int len = strlen(used_atom[i].name);
> -   if (len == ep - atom && !memcmp(used_atom[i].name, atom, len))
> -   return i;
> +   if (len == ep - atom && !memcmp(used_atom[i].name, atom, 
> len)) {
> +   *res = i;
> +   return 0;
> +   }
> }

If you did so, this hunk above would not need to be changed ...

> @@ -458,7 +465,8 @@ static int parse_ref_filter_atom(const struct ref_format 
> *format,
> need_tagged = 1;
> if (!strcmp(valid_atom[i].name, "symref"))
> need_symref = 1;
> -   return at;
> +   *res = at;
> +   return 0;
>  }

... nor this one above ...

> if (!ep)
> return error(_("malformed format string %s"), sp);
> /* sp points at "%(" and ep points at the closing ")" */
> -   at = parse_ref_filter_atom(format, sp + 2, ep);
> +   if (parse_ref_filter_atom(format, sp + 2, ep, , ))
> +   die("%s", err.buf);

And this would be more like "if (at < 0) die(...)".

> for (cp = format->format; *cp && (sp = find_next(cp)); cp = ep + 1) {
> struct atom_value *atomv;
> +   struct strbuf err = STRBUF_INIT;
> +   int pos;
>
> ep = strchr(sp, ')');
> if (cp < sp)
> append_literal(cp, sp, );
> -   get_ref_atom_value(info,
> -  parse_ref_filter_atom(format, sp + 2, ep),
> -  );
> +   if (parse_ref_filter_atom(format, sp + 2, ep, , ))
> +   return -1;
> +   get_ref_atom_value(info, pos, );
> if (atomv->handler(atomv, , error_buf))
> return -1;
> +   strbuf_release();

This looks leaky: if we get an error, we've got something in the buffer
but we do not release it because we return early. Stepping back a bit, I
wonder why we do not do anything at all with "err". Stepping back a bit
more :-) I wonder if you could get rid of "err" and pass "error_buf" to
parse_ref_filter_atom() instead. Our caller would like to have access to
the error string?

This ties back to my comment on the first patch -- "return negative if
and only if you add some error string to the buffer" might be a useful
rule?

Martin