Subject: Re: [PATCH v7 5/8] config: add `git_die_config()` to the config-set API

From: Junio C Hamano <[email-masked]>
Date: Mon, 04 Aug 2014 11:07:12 -0700

Tanay Abhra <[email-masked]> writes:

> Add `git_die_config` that dies printing the line number and the file name
> of the highest priority value for the configuration variable `key`.
>
> It has usage in non-callback based config value retrieval where we can
> raise an error and die if there is a semantic error.
> For example,
>
> 	if (!git_config_get_value(key, &value)) {
> 		/* NULL values not allowed */
> 		if (!value)
> 			git_config_die(key);
> 		else
> 			/* do work */
> 	}

It feels a bit unnatural at the API level that this does not take
'value'; I do understand that it is not a big deal in the error code
path to locate again the value from the configuration using the key,
but still.

It feels even more unnatural that the caller cannot say _how_ it
finds the value offending by not taking any message.  For one
particular callchain, e.g. git_config_get_string() that eventually
calls git_config_string() which will show an error message via
config_error_nonbool(), you may not want any extra message, but for
new callers that wants to make sure value falls within a supported
range, this forces it to write

	if (!git_config_get_int(key, &num)) {
        	if (!(0 < num && num < 4)) {
			error("'%s' must be between 1 and 3");
                        git_config_die(key);
		}
		/* otherwise work */
	}

and then the error message would say something like:

	error: 'core.frotz' must be between 1 and 3
	fatal: bad config variable 'core.frotz' at file line 15 in .git/config

which sounds somewhat backwards, at least to me.

> +NORETURN
> +void git_die_config_linenr(const char *key, const char *filename, int linenr)
> +{
> +	if (!linenr)
> +		die(_("unable to parse '%s' from command-line config"), key);

Do we have existing code that says "we signal that it is from the
command line by setting linenr to zero" already?  Otherwise I would
have thought filename == NULL would be a more sensible convention.

Otherwise OK.

> +	else
> +		die(_("bad config variable '%s' at file line %d in %s"),

At least, quote the last '%s'.

> +			key,
> +			linenr,
> +			filename);

Don't waste vertical real-estate line this.

Perhaps

        die(_("bad config variable '%s' in file '%s' at line %d"),
            key, linenr, filename);