Subject: Re: [PATCH v2 6/8] packed-backend: add "packed-refs" entry consistency check

From: Patrick Steinhardt <[email-masked]>
Date: Mon, 3 Feb 2025 09:40:25 +0100

On Thu, Jan 30, 2025 at 12:07:58PM +0800, shejialuo wrote:
> "packed-backend.c::next_record" will parse the ref entry to check the
> consistency. This function has already checked the following things:
> 
> 1. Parse the main line of the ref entry, if the oid is not correct. It
>    will die the program. And then it will check whether the next
>    character of the oid is space. Then it will check whether the refname
>    is correct.
> 2. If the next line starts with '^', it will continue to parse the oid
>    of the peeled oid content and check whether the last character is
>    '\n'.
> 
> We can iterate each line by using the "packed_fsck_ref_next_line"
> function. Then, create a new fsck message "badPackedRefEntry(ERROR)" to
> report to the user when something is wrong.
> 
> Create two new functions "packed_fsck_ref_main_line" and
> "packed_fsck_ref_peeled_line" for case 1 and case 2 respectively. Last,
> update the unit test to exercise the code.

I think this message is going into too much detail about _how_ you are
doing things compared to _what_ you are doing and what the intent is.

> diff --git a/refs/packed-backend.c b/refs/packed-backend.c
> index 870c8e7aaa..271c740728 100644
> --- a/refs/packed-backend.c
> +++ b/refs/packed-backend.c
> @@ -1819,10 +1819,86 @@ static int packed_fsck_ref_header(struct fsck_options *o, const char *start, con
>  	return 0;
>  }
>  
> +static int packed_fsck_ref_peeled_line(struct fsck_options *o,
> +				       struct ref_store *ref_store,
> +				       struct strbuf *packed_entry,
> +				       const char *start, const char *eol)
> +{
> +	struct fsck_ref_report report = { 0 };
> +	struct object_id peeled;
> +	const char *p;
> +
> +	report.path = packed_entry->buf;
> +
> +	start++;

It's a bit weird that we increment `start` here, as it is very intimate
with how the caller calls us. Might be easier to reason about when the
caller did this for us.

> +	if (parse_oid_hex_algop(start, &peeled, &p, ref_store->repo->hash_algo)) {
> +		return fsck_report_ref(o, &report,
> +				       FSCK_MSG_BAD_PACKED_REF_ENTRY,
> +				       "'%.*s' has invalid peeled oid",
> +				       (int)(eol - start), start);
> +	}

All the braces around those single-line return statements can go away.

> @@ -1843,6 +1919,26 @@ static int packed_fsck_ref_content(struct fsck_options *o,
>  				       "missing header line");
>  	}
>  
> +	while (start < eof) {
> +		strbuf_reset(&packed_entry);
> +		strbuf_addf(&packed_entry, "packed-refs line %d", line_number);
> +		ret |= packed_fsck_ref_next_line(o, &packed_entry, start, eof, &eol);
> +		ret |= packed_fsck_ref_main_line(o, ref_store, &packed_entry, &refname, start, eol);

Don't we have to stop in case `next_line()` returns an error?

Patrick