Re: [PATCH v9 1/2] add `config_set` API for caching config-like files

[Junio C Hamano <gitster@pobox.com>]

Tanay Abhra <tanayabh@gmail.com> writes:

> diff --git a/config.c b/config.c
> index ba882a1..89e2d67 100644
> --- a/config.c
> +++ b/config.c
> ...
> +const struct string_list *git_configset_get_value_multi(struct config_set *cs, const char *key)
> +{
> +	struct config_set_element *e = configset_find_element(cs, key);
> +	return e ? &e->value_list : NULL;
> +}

Somehow I find the placement of this function out of place.  Didn't
you get the same impression while proofreading the entire file after
you are done writing this patch?

The right place for it would probably be immediately before
git_configset_get_value(), I would think.

> +int git_configset_add_file(struct config_set *cs, const char *filename)
> +{
> +	int ret = 0;
> +	ret = git_config_from_file(config_hash_callback, filename, cs);
> +	if (!ret)
> +		return 0;
> +	else {
> +		git_configset_clear(cs);
> +		return -1;
> +	}
> +}

If I add contents from file "A" successfully and then attempt to
further add contents from file "B" which fails, I would lose
contents I read from "A"?

It would not be worth trying to make it transactional (i.e. making
sure cs contains what was there before the config-from-file was
called if it failed), so in such a case we may end up seeing a
mixture of full contents from A and partial contents from B, which
is just as useless as a cleared configset, so it is not wrong to
clear it per-se.  An alternative might be to return without
clearing, as we are leaving the configset in a useless state either
way and give the caller a choice between clearing it and continue,
and dying without even spending unnecessary cycles to clear.  That
might be more consistent with what git_config_check_init() does,
where you die without bothering to clear what was half-read into the
configset.

Whatever behaviour is chosen in the error codepath, it needs to be
documented.

Thanks.