[5/5] trailer: rename *_DEFAULT enums to *_UNSPECIFIED

Commit Message

Linus Arver Aug. 5, 2023, 5:04 a.m. UTC

From: Linus Arver <[e-mail]>

Do not use *_DEFAULT as a suffix to the enums, because the word
"default" is overloaded. The following are two examples of the ambiguity
of the word "default":

(1) "Default" can mean using the "default" values that are hardcoded
    in trailer.c as

        default_conf_info.where = WHERE_END;
        default_conf_info.if_exists = EXISTS_ADD_IF_DIFFERENT_NEIGHBOR;
        default_conf_info.if_missing = MISSING_ADD;

    in ensure_configured(). These values are referred to as "the
    default" in the docs for interpret-trailers. These defaults are used
    if no "trailer.*" configurations are defined.

(2) "Default" can also mean the "trailer.*" configurations themselves,
    because these configurations are used by "default" (ahead of the
    hardcoded defaults in (1)) if no command line arguments are
    provided.

In addition, the corresponding *_DEFAULT values are chosen when the user
provides the "--no-where", "--no-if-exists", or "--no-if-missing" flags
on the command line. These "--no-*" flags are used to clear previously
provided flags of the form "--where", "--if-exists", and "--if-missing".
Using these "--no-*" flags undoes the specifying of these flags (if
any), so using the word "UNSPECIFIED" is more natural here.

So instead of using "*_DEFAULT", use "*_UNSPECIFIED" because this
signals to the reader that the *_UNSPECIFIED value by itself carries no
meaning (it's a zero value and by itself does not "default" to anything,
necessitating the need to have some other way of getting to a useful
value).

Signed-off-by: Linus Arver <[e-mail]>
---
 trailer.c | 17 ++++++++++-------
 trailer.h |  6 +++---
 2 files changed, 13 insertions(+), 10 deletions(-)

Comments

Glen Choo Aug. 7, 2023, 11:45 p.m. UTC | #1

"Linus Arver via GitGitGadget" <[e-mail]> writes:

> (2) "Default" can also mean the "trailer.*" configurations themselves,
>     because these configurations are used by "default" (ahead of the
>     hardcoded defaults in (1)) if no command line arguments are
>     provided.

Interesting, I would have never thought of config as 'default'. In fact,
I would have thought that this de facto behavior (which you also
clarified in [1]) is a bug if not for the fact that in an internal
version of this series, you cited a commit message that describes this
as expected behavior. That context would be very welcome in the ML, I
think.

[1] https://lore.kernel.org/git/6b42[e-mail]

> In addition, the corresponding *_DEFAULT values are chosen when the user
> provides the "--no-where", "--no-if-exists", or "--no-if-missing" flags
> on the command line. These "--no-*" flags are used to clear previously
> provided flags of the form "--where", "--if-exists", and "--if-missing".
> Using these "--no-*" flags undoes the specifying of these flags (if
> any), so using the word "UNSPECIFIED" is more natural here.
>
> So instead of using "*_DEFAULT", use "*_UNSPECIFIED" because this
> signals to the reader that the *_UNSPECIFIED value by itself carries no
> meaning (it's a zero value and by itself does not "default" to anything,
> necessitating the need to have some other way of getting to a useful
> value).

Makse sense. This seems like a good change.

> @@ -586,7 +586,10 @@ static void ensure_configured(void)
>  	if (configured)
>  		return;
>  
> -	/* Default config must be setup first */
> +	/*
> +	 * Default config must be setup first. These defaults are used if there
> +	 * are no "trailer.*" or "trailer.<token>.*" options configured.
> +	 */
>  	default_conf_info.where = WHERE_END;
>  	default_conf_info.if_exists = EXISTS_ADD_IF_DIFFERENT_NEIGHBOR;
>  	default_conf_info.if_missing = MISSING_ADD;

As mentioned earlier, I find it a bit odd that we're calling config
'default' (and also that we're calling CLI args config), but
renaming default_conf_info to config_conf_info sounds worse, so let's
leave it as-is.

Linus Arver Aug. 11, 2023, 6 p.m. UTC | #2

Glen Choo <[e-mail]> writes:

> "Linus Arver via GitGitGadget" <[e-mail]> writes:
>
>> (2) "Default" can also mean the "trailer.*" configurations themselves,
>>     because these configurations are used by "default" (ahead of the
>>     hardcoded defaults in (1)) if no command line arguments are
>>     provided.
>
> Interesting, I would have never thought of config as 'default'. In fact,
> I would have thought that this de facto behavior (which you also
> clarified in [1]) is a bug if not for the fact that in an internal
> version of this series, you cited a commit message that describes this
> as expected behavior. That context would be very welcome in the ML, I
> think.
>
> [1] https://lore.kernel.org/git/6b42[e-mail]

I forget the internal version/discussion, but I assume you're thinking
of 0ea5292e6b (interpret-trailers: add options for actions, 2017-08-01).
I will reroll and mention it to the commit message.

>> In addition, the corresponding *_DEFAULT values are chosen when the user
>> provides the "--no-where", "--no-if-exists", or "--no-if-missing" flags
>> on the command line. These "--no-*" flags are used to clear previously
>> provided flags of the form "--where", "--if-exists", and "--if-missing".
>> Using these "--no-*" flags undoes the specifying of these flags (if
>> any), so using the word "UNSPECIFIED" is more natural here.
>>
>> So instead of using "*_DEFAULT", use "*_UNSPECIFIED" because this
>> signals to the reader that the *_UNSPECIFIED value by itself carries no
>> meaning (it's a zero value and by itself does not "default" to anything,
>> necessitating the need to have some other way of getting to a useful
>> value).
>
> Makse sense. This seems like a good change.
>
>> @@ -586,7 +586,10 @@ static void ensure_configured(void)
>>  	if (configured)
>>  		return;
>>  
>> -	/* Default config must be setup first */
>> +	/*
>> +	 * Default config must be setup first. These defaults are used if there
>> +	 * are no "trailer.*" or "trailer.<token>.*" options configured.
>> +	 */
>>  	default_conf_info.where = WHERE_END;
>>  	default_conf_info.if_exists = EXISTS_ADD_IF_DIFFERENT_NEIGHBOR;
>>  	default_conf_info.if_missing = MISSING_ADD;
>
> As mentioned earlier, I find it a bit odd that we're calling config
> 'default' (and also that we're calling CLI args config), but
> renaming default_conf_info to config_conf_info sounds worse, so let's
> leave it as-is.

SGTM. Although, we could also just rename it to "conf_info" (same name
as the struct name). Unless such same-variable-name-as-the-struct is
discouraged in the codebase.

Patch

diff --git a/trailer.c b/trailer.c
index 3b9ce199636..c49826decae 100644
--- a/trailer.c
+++ b/trailer.c
@@ -388,7 +388,7 @@  static void process_trailers_lists(struct list_head *head,
 int trailer_set_where(enum trailer_where *item, const char *value)
 {
 	if (!value)
-		*item = WHERE_DEFAULT;
+		*item = WHERE_UNSPECIFIED;
 	else if (!strcasecmp("after", value))
 		*item = WHERE_AFTER;
 	else if (!strcasecmp("before", value))
@@ -405,7 +405,7 @@  int trailer_set_where(enum trailer_where *item, const char *value)
 int trailer_set_if_exists(enum trailer_if_exists *item, const char *value)
 {
 	if (!value)
-		*item = EXISTS_DEFAULT;
+		*item = EXISTS_UNSPECIFIED;
 	else if (!strcasecmp("addIfDifferent", value))
 		*item = EXISTS_ADD_IF_DIFFERENT;
 	else if (!strcasecmp("addIfDifferentNeighbor", value))
@@ -424,7 +424,7 @@  int trailer_set_if_exists(enum trailer_if_exists *item, const char *value)
 int trailer_set_if_missing(enum trailer_if_missing *item, const char *value)
 {
 	if (!value)
-		*item = MISSING_DEFAULT;
+		*item = MISSING_UNSPECIFIED;
 	else if (!strcasecmp("doNothing", value))
 		*item = MISSING_DO_NOTHING;
 	else if (!strcasecmp("add", value))
@@ -586,7 +586,10 @@  static void ensure_configured(void)
 	if (configured)
 		return;
 
-	/* Default config must be setup first */
+	/*
+	 * Default config must be setup first. These defaults are used if there
+	 * are no "trailer.*" or "trailer.<token>.*" options configured.
+	 */
 	default_conf_info.where = WHERE_END;
 	default_conf_info.if_exists = EXISTS_ADD_IF_DIFFERENT_NEIGHBOR;
 	default_conf_info.if_missing = MISSING_ADD;
@@ -701,11 +704,11 @@  static void add_arg_item(struct list_head *arg_head, char *tok, char *val,
 	new_item->value = val;
 	duplicate_conf(&new_item->conf, conf);
 	if (new_trailer_item) {
-		if (new_trailer_item->where != WHERE_DEFAULT)
+		if (new_trailer_item->where != WHERE_UNSPECIFIED)
 			new_item->conf.where = new_trailer_item->where;
-		if (new_trailer_item->if_exists != EXISTS_DEFAULT)
+		if (new_trailer_item->if_exists != EXISTS_UNSPECIFIED)
 			new_item->conf.if_exists = new_trailer_item->if_exists;
-		if (new_trailer_item->if_missing != MISSING_DEFAULT)
+		if (new_trailer_item->if_missing != MISSING_UNSPECIFIED)
 			new_item->conf.if_missing = new_trailer_item->if_missing;
 	}
 	list_add_tail(&new_item->list, arg_head);
diff --git a/trailer.h b/trailer.h
index db57e028650..924cf5405c6 100644
--- a/trailer.h
+++ b/trailer.h
@@ -5,14 +5,14 @@ 
 #include "strbuf.h"
 
 enum trailer_where {
-	WHERE_DEFAULT,
+	WHERE_UNSPECIFIED,
 	WHERE_END,
 	WHERE_AFTER,
 	WHERE_BEFORE,
 	WHERE_START
 };
 enum trailer_if_exists {
-	EXISTS_DEFAULT,
+	EXISTS_UNSPECIFIED,
 	EXISTS_ADD_IF_DIFFERENT_NEIGHBOR,
 	EXISTS_ADD_IF_DIFFERENT,
 	EXISTS_ADD,
@@ -20,7 +20,7 @@  enum trailer_if_exists {
 	EXISTS_DO_NOTHING
 };
 enum trailer_if_missing {
-	MISSING_DEFAULT,
+	MISSING_UNSPECIFIED,
 	MISSING_ADD,
 	MISSING_DO_NOTHING
 };