Re: [PATCH v2 06/10] parse-options: mark unused "opt" parameter in callbacks

["René Scharfe" <l.s.r@web.de>]

Am 31.08.23 um 23:21 schrieb Jeff King:
> The previous commit argued that parse-options callbacks should try to
> use opt->value rather than touching globals directly. In some cases,
> however, that's awkward to do. Some callbacks touch multiple variables,
> or may even just call into an abstracted function that does so.
>
> In some of these cases we _could_ convert them by stuffing the multiple
> variables into a single struct and passing the struct pointer through
> opt->value. But that may make other parts of the code less readable,
> as the struct relationship has to be mentioned everywhere.

Does that imply you'd be willing to use other methods?  Let's find out
below. :)

>
> Let's just accept that these cases are special and leave them as-is. But
> we do need to mark their "opt" parameters to satisfy -Wunused-parameter.
>
> Signed-off-by: Jeff King <peff@peff.net>
> ---
>  builtin/gc.c           |  2 +-
>  builtin/log.c          | 10 ++++++----
>  builtin/merge.c        |  2 +-
>  builtin/pack-objects.c |  6 +++---
>  builtin/read-tree.c    |  2 +-
>  builtin/update-index.c |  4 ++--
>  6 files changed, 14 insertions(+), 12 deletions(-)
>
> diff --git a/builtin/gc.c b/builtin/gc.c
> index 369bd43fb2..b842349d86 100644
> --- a/builtin/gc.c
> +++ b/builtin/gc.c
> @@ -1403,7 +1403,7 @@ static void initialize_task_config(int schedule)
>  	strbuf_release(&config_name);
>  }
>
> -static int task_option_parse(const struct option *opt,
> +static int task_option_parse(const struct option *opt UNUSED,

Only the global variable "tasks" seems to be used in here if you don't
count the constant "TASK__COUNT", so you could pass it in.  This could
also be converted to OPT_STRING_LIST with parsing and duplicate checking
done later.

And I don't understand why the callback returns 1 (PARSE_OPT_NON_OPTION)
on error, but that's a different matter.

>  			     const char *arg, int unset)
>  {
>  	int i, num_selected = 0;
> diff --git a/builtin/log.c b/builtin/log.c
> index fb90d43717..3599063554 100644
> --- a/builtin/log.c
> +++ b/builtin/log.c
> @@ -118,16 +118,17 @@ static struct string_list decorate_refs_exclude = STRING_LIST_INIT_NODUP;
>  static struct string_list decorate_refs_exclude_config = STRING_LIST_INIT_NODUP;
>  static struct string_list decorate_refs_include = STRING_LIST_INIT_NODUP;
>
> -static int clear_decorations_callback(const struct option *opt,
> -					    const char *arg, int unset)
> +static int clear_decorations_callback(const struct option *opt UNUSED,
> +				      const char *arg, int unset)
>  {
>  	string_list_clear(&decorate_refs_include, 0);
>  	string_list_clear(&decorate_refs_exclude, 0);
>  	use_default_decoration_filter = 0;
>  	return 0;
>  }
>

Meta: Why do we get seven lines of context in an -U3 patch here?  Did
you use --inter-hunk-context?

This patch would be better viewed with --function-context to see that
the callbacks change multiple variables or do other funky things.  Only
doubles the line count.

> -static int decorate_callback(const struct option *opt, const char *arg, int unset)
> +static int decorate_callback(const struct option *opt UNUSED, const char *arg,
> +			     int unset)
>  {
>  	if (unset)
>  		decoration_style = 0;

Sets decoration_style and decoration_given.  Never sets decoration_given
to a negative value.  This could be used to initialize decoration_style
to -1 and set decoration_given after parsing, then you could pass in
just decoration_style.

> @@ -1555,7 +1556,8 @@ static int inline_callback(const struct option *opt, const char *arg, int unset)
>  	return 0;
>  }
>
> -static int header_callback(const struct option *opt, const char *arg, int unset)
> +static int header_callback(const struct option *opt UNUSED, const char *arg,

Sorts strings into three string_lists based on prefix.  Could become a
vanilla OPT_STRING_LIST with parsing and sorting done later, if it
wouldn't interact with to_callback() and cc_callback().

(--function-context is not enough to see that, it requires a look at the
definition of those other functions as well.)

> +			   int unset)
>  {
>  	if (unset) {
>  		string_list_clear(&extra_hdr, 0);
> diff --git a/builtin/merge.c b/builtin/merge.c
> index 21363b7985..0436986dab 100644
> --- a/builtin/merge.c
> +++ b/builtin/merge.c
> @@ -231,7 +231,7 @@ static void append_strategy(struct strategy *s)
>  	use_strategies[use_strategies_nr++] = s;
>  }
>
> -static int option_parse_strategy(const struct option *opt,
> +static int option_parse_strategy(const struct option *opt UNUSED,

Could be an OPT_STRING_LIST and parsing done later.  Except that
--no-strategy does nothing, which is weird.

>  				 const char *name, int unset)
>  {
>  	if (unset)
> diff --git a/builtin/pack-objects.c b/builtin/pack-objects.c
> index 492372ee5d..91b4b7c177 100644
> --- a/builtin/pack-objects.c
> +++ b/builtin/pack-objects.c
> @@ -3739,7 +3739,7 @@ static void show_object__ma_allow_promisor(struct object *obj, const char *name,
>  	show_object(obj, name, data);
>  }
>
> -static int option_parse_missing_action(const struct option *opt,
> +static int option_parse_missing_action(const struct option *opt UNUSED,

Sets the enum arg_missing_action, fetch_if_missing and fn_show_object.
Could be changed to set only the enum and then you could pass it in.

>  				       const char *arg, int unset)
>  {
>  	assert(arg);
> @@ -4150,7 +4150,7 @@ static int option_parse_index_version(const struct option *opt,
>  	return 0;
>  }
>
> -static int option_parse_unpack_unreachable(const struct option *opt,
> +static int option_parse_unpack_unreachable(const struct option *opt UNUSED,

Sets both unpack_unreachable and unpack_unreachable_expiration.  Perhaps
could set only unpack_unreachable_expiration and use TIME_MAX if no
argument is given, then set unpack_unreachable after parsing?  Not sure.

>  					   const char *arg, int unset)
>  {
>  	if (unset) {
> @@ -4165,7 +4165,7 @@ static int option_parse_unpack_unreachable(const struct option *opt,
>  	return 0;
>  }
>
> -static int option_parse_cruft_expiration(const struct option *opt,
> +static int option_parse_cruft_expiration(const struct option *opt UNUSED,

Does the same as option_parse_unpack_unreachable(), just with two
different variables.  And interacts with --cruft.

>  					 const char *arg, int unset)
>  {
>  	if (unset) {
> diff --git a/builtin/read-tree.c b/builtin/read-tree.c
> index 1fec702a04..8196ca9dd8 100644
> --- a/builtin/read-tree.c
> +++ b/builtin/read-tree.c
> @@ -49,7 +49,7 @@ static const char * const read_tree_usage[] = {
>  	NULL
>  };
>
> -static int index_output_cb(const struct option *opt, const char *arg,
> +static int index_output_cb(const struct option *opt UNUSED, const char *arg,

Calls set_alternate_index_output().  Could become an OPT_STRING_F if we
assume that the last value wins and earlier calls have no side effects.

>  				 int unset)
>  {
>  	BUG_ON_OPT_NEG(unset);
> diff --git a/builtin/update-index.c b/builtin/update-index.c
> index aee3cb8cbd..59acae3336 100644
> --- a/builtin/update-index.c
> +++ b/builtin/update-index.c
> @@ -856,7 +856,7 @@ static int chmod_callback(const struct option *opt,
>  	return 0;
>  }
>
> -static int resolve_undo_clear_callback(const struct option *opt,
> +static int resolve_undo_clear_callback(const struct option *opt UNUSED,

Affects the_index.  This option (--clear-resolve-undo) is not mentioned
in Documentation/, by the way.  Not sure if it interacts with other
callbacks, like the one below.  Otherwise could be an OPT_BOOL and its
action done after parsing.  Perhaps pass in &the_index?

>  				const char *arg, int unset)
>  {
>  	BUG_ON_OPT_NEG(unset);
> @@ -890,7 +890,7 @@ static int parse_new_style_cacheinfo(const char *arg,
>  }
>
>  static enum parse_opt_result cacheinfo_callback(
> -	struct parse_opt_ctx_t *ctx, const struct option *opt,
> +	struct parse_opt_ctx_t *ctx, const struct option *opt UNUSED,

A low-level callback for a change.  Affects the_index.  Pass it in?
add_cacheinfo() would need to grow a parameter to receive it.  It would
document that this option directly changes the_index.

>  	const char *arg, int unset)
>  {
>  	struct object_id oid;

Phew, looks like that's stuff for a whole new series or two!

René