Subject: Re: [GSoC][PATCH v13 02/10] fsck: add a unified interface for reporting fsck messages

From: Patrick Steinhardt <[email-masked]>
Date: Tue, 30 Jul 2024 10:31:16 +0200

On Mon, Jul 29, 2024 at 09:26:30PM +0800, shejialuo wrote:
> The static function "report" provided by "fsck.c" aims at checking fsck
> error type and calling the callback "error_func" to report the message.
> However, "report" function is only related to object database which
> cannot be reused for refs.

Nit: it would be nice to mention _why_ it cannot be reused for refs.

> diff --git a/fsck.c b/fsck.c
> index 3f32441492..1185e9a8ad 100644
> --- a/fsck.c
> +++ b/fsck.c
> @@ -226,12 +226,18 @@ static int object_on_skiplist(struct fsck_options *opts,
>  	return opts && oid && oidset_contains(&opts->skip_oids, oid);
>  }
>  
> -__attribute__((format (printf, 5, 6)))
> -static int report(struct fsck_options *options,
> -		  const struct object_id *oid, enum object_type object_type,
> -		  enum fsck_msg_id msg_id, const char *fmt, ...)
> +/*
> + * Provide a unified interface for either fscking refs or objects.
> + * It will get the current msg error type and call the error_func callback
> + * which is registered in the "fsck_options" struct.
> + */
> +static int fsck_vreport(struct fsck_options *options,
> +			const struct object_id *oid,
> +			enum object_type object_type,
> +			const struct fsck_refs_info *refs_info,
> +			enum fsck_msg_id msg_id, const char *fmt, va_list ap)
>  {
> -	va_list ap;
> +	va_list ap_copy;
>  	struct strbuf sb = STRBUF_INIT;
>  	enum fsck_msg_type msg_type = fsck_msg_type(msg_id, options);
>  	int result;

It is a bit weird that this new generic function receives non-generic
inputs which are specific to the respective subsystems (objects or refs)
that we are checking.

A better design would likely be to make `error_func()` receive a void
pointer such that `error_func()` and then have the respective subsystems
provide a function that knows to format the message while receiving
either a `struct fsck_object_report *` or a `struct fsck_ref_report *`.

I don't think this is particularly worriesome though as it is still
manageable right now. So I'm fine if we want to leave this as-is, and
then we can iterate on this in a future patch series as required.

> @@ -250,9 +256,9 @@ static int report(struct fsck_options *options,
>  	prepare_msg_ids();
>  	strbuf_addf(&sb, "%s: ", msg_id_info[msg_id].camelcased);
>  
> -	va_start(ap, fmt);
> -	strbuf_vaddf(&sb, fmt, ap);
> -	result = options->error_func(options, oid, object_type,
> +	va_copy(ap_copy, ap);
> +	strbuf_vaddf(&sb, fmt, ap_copy);
> +	result = options->error_func(options, oid, object_type, refs_info,
>  				     msg_type, msg_id, sb.buf);
>  	strbuf_release(&sb);
>  	va_end(ap);
> @@ -260,6 +266,35 @@ static int report(struct fsck_options *options,
>  	return result;
>  }
>  
> +__attribute__((format (printf, 5, 6)))
> +static int report(struct fsck_options *options,
> +		  const struct object_id *oid, enum object_type object_type,
> +		  enum fsck_msg_id msg_id, const char *fmt, ...)
> +{
> +	va_list ap;
> +	int result;
> +
> +	va_start(ap, fmt);
> +	result = fsck_vreport(options, oid, object_type, NULL, msg_id, fmt, ap);
> +	va_end(ap);
> +
> +	return result;
> +}

As far as I can see, `report()` is now specific to reporting errors with
objects while `fsck_vreport()` is the generic part. Do we want to rename
the function to `fsck_report_object()` to clarify, or would that cause
too much churn?

Hm. Seeing that we have 62 callsites of that function it may be too much
churn indeed.

> +int fsck_refs_report(struct fsck_options *options,
> +		     const struct object_id *oid,
> +		     const struct fsck_refs_info *refs_info,
> +		     enum fsck_msg_id msg_id, const char *fmt, ...)

Would `fsck_report_ref()` be a better name?

What is the intent of the `oid` field? Would it be set to the object ID
that a reference points to? What if the reference is a non-resolving
symbolic reference? I wonder whether we can just remove it.

Patrick