Subject: Re: [PATCH v2 3/5] read-cache & fetch-negotiator: check "enum" values in switch()

From: Junio C Hamano <[email-masked]>
Date: Fri, 17 Sep 2021 12:30:21 -0700

Ævar Arnfjörð Bjarmason  <[email-masked]> writes:

> 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".
>
> 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".

Covering all possibility is good, but ...

>
> Signed-off-by: Ævar Arnfjörð Bjarmason <[email-masked]>
> ---
>  fetch-negotiator.c |  3 ++-
>  read-cache.c       | 15 ++++++++++-----
>  2 files changed, 12 insertions(+), 6 deletions(-)
>
> diff --git a/fetch-negotiator.c b/fetch-negotiator.c
> index 57ed5784e14..e7b5878be7c 100644
> --- a/fetch-negotiator.c
> +++ b/fetch-negotiator.c
> @@ -19,7 +19,8 @@ void fetch_negotiator_init(struct repository *r,
>  		return;
>  
>  	case FETCH_NEGOTIATION_DEFAULT:
> -	default:
> +	case FETCH_NEGOTIATION_UNSET:
> +	case FETCH_NEGOTIATION_NONE:
>  		default_negotiator_init(negotiator);
>  		return;
>  	}
> diff --git a/read-cache.c b/read-cache.c
> index 9048ef9e905..9dd84d69f00 100644
> --- a/read-cache.c
> +++ b/read-cache.c
> @@ -1944,13 +1944,18 @@ static void tweak_untracked_cache(struct index_state *istate)
>  
>  	prepare_repo_settings(r);
>  
> -	if (r->settings.core_untracked_cache  == UNTRACKED_CACHE_REMOVE) {
> +	switch (r->settings.core_untracked_cache) {
> +	case UNTRACKED_CACHE_REMOVE:
>  		remove_untracked_cache(istate);
> -		return;
> -	}
> -
> -	if (r->settings.core_untracked_cache == UNTRACKED_CACHE_WRITE)
> +		break;
> +	case UNTRACKED_CACHE_WRITE:
>  		add_untracked_cache(istate);
> +		break;
> +	case UNTRACKED_CACHE_UNSET:
> +	case UNTRACKED_CACHE_KEEP:
> +		break;
> +	}

... this change makes me wonder if

	default:
		BUG(...);

might have been more appropriate?  Are we sure these the flow will
reach here with these two values?

> +	return;
>  }

I do not see why we want to add a no-op return that wasn't there in
the original.  Perhaps later, but definitely not as a part of this
change.

>  
>  static void tweak_split_index(struct index_state *istate)