Subject: Re: [PATCH v3 3/5] read-cache & fetch-negotiator: check "enum" values in switch()

From: Taylor Blau <[email-masked]>
Date: Mon, 20 Sep 2021 18:14:44 -0400

On Sun, Sep 19, 2021 at 10:47:17AM +0200, Ævar Arnfjörð Bjarmason wrote:
> Change tweak_untracked_cache() in "read-cache.c" to use a switch() to
> have the compiler assert that we checked all possible values in the
> "enum untracked_cache_setting" type, and likewise remove the "default"
> case in fetch_negotiator_init() in favor of checking for
> "FETCH_NEGOTIATION_UNSET" and "FETCH_NEGOTIATION_NONE".
>
> As will be discussed in a subsequent we'll only ever have either of

s/subsequent/& patch/ ?

> these set to FETCH_NEGOTIATION_NONE, FETCH_NEGOTIATION_UNSET and
> UNTRACKED_CACHE_UNSET within the prepare_repo_settings() function
> itself. In preparation for fixing that code let's add a BUG() here to
> mark this as unreachable code.
>
> See ad0fb659993 (repo-settings: parse core.untrackedCache, 2019-08-13)
> for when the "unset" and "keep" handling for core.untrackedCache was
> consolidated, and aaf633c2ad1 (repo-settings: create
> feature.experimental setting, 2019-08-13) for the addition of the
> "default" pattern in "fetch-negotiator.c".
>
> Signed-off-by: Ævar Arnfjörð Bjarmason <[email-masked]>
> ---
>  fetch-negotiator.c |  4 +++-
>  read-cache.c       | 15 ++++++++++-----
>  2 files changed, 13 insertions(+), 6 deletions(-)
>
> diff --git a/fetch-negotiator.c b/fetch-negotiator.c
> index 57ed5784e14..237f92b8696 100644
> --- a/fetch-negotiator.c
> +++ b/fetch-negotiator.c
> @@ -19,8 +19,10 @@ void fetch_negotiator_init(struct repository *r,
>  		return;
>
>  	case FETCH_NEGOTIATION_DEFAULT:
> -	default:
>  		default_negotiator_init(negotiator);
>  		return;
> +	case FETCH_NEGOTIATION_NONE:
> +	case FETCH_NEGOTIATION_UNSET:
> +		BUG("FETCH_NEGOTIATION_UNSET only in prepare_repo_settings()");

I was briefly confused why this BUG message mentioned
FETCH_NEGOTIATION_UNSET, since we only support FETCH_NEGOTIATION_DEFAULT
here.

But then I realized that it said "only in prepare_repo_settings()", and
we're in fetch_negotiator_init(). So this makes sense to me.

Other than the small typo in the patch message, this looks good to me.

Thanks,
Taylor