Subject: Re: [PATCH 4/7] add object_as_type helper for casting objects

From: Ramsay Jones <[email-masked]>
Date: Fri, 11 Jul 2014 11:45:58 +0100

On 11/07/14 09:48, Jeff King wrote:

[snip]

> diff --git a/object.c b/object.c
> index 472aa8d..b2319f6 100644
> --- a/object.c
> +++ b/object.c
> @@ -158,6 +158,23 @@ void *create_object(const unsigned char *sha1, void *o)
>  	return obj;
>  }
>  
> +void *object_as_type(struct object *obj, enum object_type type, int quiet)
> +{
> +	if (obj->type == type)
> +		return obj;
> +	else if (obj->type == OBJ_NONE) {
> +		obj->type = type;
> +		return obj;
> +	}
> +	else {
> +		if (!quiet)
> +			error("object %s is a %s, not a %s",
> +			      sha1_to_hex(obj->sha1),
> +			      typename(obj->type), typename(type));
> +		return NULL;
> +	}
> +}
> +
>  struct object *lookup_unknown_object(const unsigned char *sha1)
>  {
>  	struct object *obj = lookup_object(sha1);
> diff --git a/object.h b/object.h
> index 8020ace..5e8d8ee 100644
> --- a/object.h
> +++ b/object.h
> @@ -81,6 +81,8 @@ struct object *lookup_object(const unsigned char *sha1);
>  
>  extern void *create_object(const unsigned char *sha1, void *obj);
>  
> +void *object_as_type(struct object *obj, enum object_type type, int quiet);
> +
>  /*
>   * Returns the object, having parsed it to find out what it is.
>   *
> diff --git a/refs.c b/refs.c
> index 20e2bf1..5a18e2d 100644
> --- a/refs.c
> +++ b/refs.c
> @@ -1729,9 +1729,8 @@ static enum peel_status peel_object(const unsigned char *name, unsigned char *sh
>  
>  	if (o->type == OBJ_NONE) {
>  		int type = sha1_object_info(name, NULL);
> -		if (type < 0)
> +		if (type < 0 || !object_as_type(o, type, 0))
--------------------------------------------------------^^^

It is not possible here for object_as_type() to issue an error()
report, but I had to go look at the code to check. (It would have
been a change in behaviour, otherwise). So, it doesn't really matter
what you pass to the quiet argument, but setting it to 1 _may_ help
the next reader. (No, I'm not convinced either; the only reason I
knew it had anything to do with error messages was because I had
just read the code ...) Hmm, dunno.

>  			return PEEL_INVALID;
> -		o->type = type;
>  	}
>  
>  	if (o->type != OBJ_TAG)
> diff --git a/tag.c b/tag.c
> index 79552c7..82d841b 100644
> --- a/tag.c
> +++ b/tag.c
> @@ -41,14 +41,7 @@ struct tag *lookup_tag(const unsigned char *sha1)
>  	struct object *obj = lookup_object(sha1);
>  	if (!obj)
>  		return create_object(sha1, alloc_tag_node());
> -	if (!obj->type)
> -		obj->type = OBJ_TAG;
> -	if (obj->type != OBJ_TAG) {
> -		error("Object %s is a %s, not a tag",
> -		      sha1_to_hex(sha1), typename(obj->type));
> -		return NULL;
> -	}
> -	return (struct tag *) obj;
> +	return object_as_type(obj, OBJ_TAG, 0);
>  }
>  
>  static unsigned long parse_tag_date(const char *buf, const char *tail)
> diff --git a/tree.c b/tree.c
> index ed66575..bb02c1c 100644
> --- a/tree.c
> +++ b/tree.c
> @@ -184,14 +184,7 @@ struct tree *lookup_tree(const unsigned char *sha1)
>  	struct object *obj = lookup_object(sha1);
>  	if (!obj)
>  		return create_object(sha1, alloc_tree_node());
> -	if (!obj->type)
> -		obj->type = OBJ_TREE;
> -	if (obj->type != OBJ_TREE) {
> -		error("Object %s is a %s, not a tree",
> -		      sha1_to_hex(sha1), typename(obj->type));
> -		return NULL;
> -	}
> -	return (struct tree *) obj;
> +	return object_as_type(obj, OBJ_TREE, 0);
>  }
>  
>  int parse_tree_buffer(struct tree *item, void *buffer, unsigned long size)
> 

ATB,
Ramsay Jones