lib-sieve: Implemented sieve_implicit_extensions setting.

The extensions listed in this setting do not need to be enabled explicitly using the Sieve require command.
This behavior voilates the standard, but is necessary for compatibility with some existing implementations of Sieve.
Do not use this setting unless you really need to!

src/lib-sieve/sieve-extensions.c

@@ -273,13 +273,21 @@ void sieve_extensions_configure(struct sieve_instance *svinst)
 
 	/* Apply sieve_extensions configuration */
 
-	if ( (extensions=sieve_setting_get(svinst, "sieve_extensions")) != NULL )
-		sieve_extensions_set_string(svinst, extensions, FALSE);
+	if ( (extensions=sieve_setting_get
+		(svinst, "sieve_extensions")) != NULL )
+		sieve_extensions_set_string(svinst, extensions, FALSE, FALSE);
 
 	/* Apply sieve_global_extensions configuration */
 
-	if ( (extensions=sieve_setting_get(svinst, "sieve_global_extensions")) != NULL )
-		sieve_extensions_set_string(svinst, extensions, TRUE);
+	if ( (extensions=sieve_setting_get
+		(svinst, "sieve_global_extensions")) != NULL )
+		sieve_extensions_set_string(svinst, extensions, TRUE, FALSE);
+
+	/* Apply sieve_implicit_extensions configuration */
+
+	if ( (extensions=sieve_setting_get
+		(svinst, "sieve_implicit_extensions")) != NULL )
+		sieve_extensions_set_string(svinst, extensions, FALSE, TRUE);
 }
 
 void sieve_extensions_deinit(struct sieve_instance *svinst)
@@ -494,13 +502,23 @@ void sieve_extension_override
 	(*mod_ext)->overridden = TRUE;
 }
 
-int sieve_extensions_get_count(struct sieve_instance *svinst)
+unsigned int sieve_extensions_get_count(struct sieve_instance *svinst)
 {
 	struct sieve_extension_registry *ext_reg = svinst->ext_reg;
 
 	return array_count(&ext_reg->extensions);
 }
 
+const struct sieve_extension *const *
+sieve_extensions_get_all(struct sieve_instance *svinst,
+	unsigned int *count_r)
+{
+	struct sieve_extension_registry *ext_reg = svinst->ext_reg;
+
+	return (const struct sieve_extension *const *)
+		array_get(&ext_reg->extensions, count_r);
+}
+
 const struct sieve_extension *sieve_extension_get_by_id
 (struct sieve_instance *svinst, unsigned int ext_id)
 {
@@ -580,7 +598,6 @@ static void sieve_extension_set_enabled
 {
 	if ( enabled ) {
 		ext->enabled = TRUE;
-		ext->global = FALSE;
 
 		if ( !ext->loaded ) {
 			(void)_sieve_extension_load(ext);
@@ -596,21 +613,27 @@ static void sieve_extension_set_global
 (struct sieve_extension *ext, bool enabled)
 {
 	if ( enabled ) {
-		ext->enabled = TRUE;
+		sieve_extension_set_enabled(ext, TRUE);
 		ext->global = TRUE;
-
-		if ( !ext->loaded ) {
-			(void)_sieve_extension_load(ext);
-		}
-
-		ext->loaded = TRUE;
 	} else {
 		ext->global = FALSE;
 	}
 }
 
+static void sieve_extension_set_implicit
+(struct sieve_extension *ext, bool enabled)
+{
+	if ( enabled ) {
+		sieve_extension_set_enabled(ext, TRUE);
+		ext->implicit = TRUE;
+	} else {
+		ext->implicit = FALSE;
+	}
+}
+
 void sieve_extensions_set_string
-(struct sieve_instance *svinst, const char *ext_string, bool global)
+(struct sieve_instance *svinst, const char *ext_string,
+	bool global, bool implicit)
 {
 	struct sieve_extension_registry *ext_reg = svinst->ext_reg;
 	ARRAY(const struct sieve_extension *) enabled_extensions;
@@ -623,7 +646,7 @@ void sieve_extensions_set_string
 	bool relative = FALSE;
 
 	if ( ext_string == NULL ) {
-		if ( global ) return;
+		if ( global || implicit ) return;
 
 		/* Enable all */
 		exts = array_get_modifiable(&ext_reg->extensions, &ext_count);
@@ -696,6 +719,8 @@ void sieve_extensions_set_string
 			if ( relative ) {
 				if ( global )
 					enabled = exts[i]->global;
+				else if ( implicit )
+					enabled = exts[i]->implicit;
 				else
 					enabled = exts[i]->enabled;
 
@@ -722,6 +747,8 @@ void sieve_extensions_set_string
 			/* Perform actual activation/deactivation */
 			if ( global ) {
 				sieve_extension_set_global(exts[i], enabled);
+			} else if ( implicit ) {
+				sieve_extension_set_implicit(exts[i], enabled);
 			} else {
 				sieve_extension_set_enabled(exts[i], enabled);
 			}

src/lib-sieve/sieve-extensions.h

@@ -95,6 +95,7 @@ struct sieve_extension {
 	unsigned int enabled:1;
 	unsigned int dummy:1;
 	unsigned int global:1;
+	unsigned int implicit:1;
 	unsigned int overridden:1;
 };
 
@@ -142,7 +143,10 @@ void sieve_extension_override
 	(struct sieve_instance *svinst, const char *name,
 		const struct sieve_extension *ext);
 
-int sieve_extensions_get_count(struct sieve_instance *svinst);
+unsigned int sieve_extensions_get_count(struct sieve_instance *svinst);
+const struct sieve_extension *const *
+sieve_extensions_get_all(struct sieve_instance *svinst,
+	unsigned int *count_r);
 
 const struct sieve_extension *sieve_extension_get_by_id
 	(struct sieve_instance *svinst, unsigned int ext_id);
@@ -152,7 +156,8 @@ const struct sieve_extension *sieve_extension_get_by_name
 const char *sieve_extensions_get_string
 	(struct sieve_instance *svinst);
 void sieve_extensions_set_string
-	(struct sieve_instance *svinst, const char *ext_string, bool global);
+	(struct sieve_instance *svinst, const char *ext_string,
+		bool global, bool implicit);
 
 const struct sieve_extension *sieve_get_match_type_extension
 	(struct sieve_instance *svinst);

src/lib-sieve/sieve-validator.c

@@ -1372,10 +1372,20 @@ static bool sieve_validate_block
 				&& !valdtr->finished_require &&
 				strcasecmp(cmd_node->identifier, cmd_require.identifier) != 0 ) {
 				const struct sieve_validator_extension_reg *extrs;
+				const struct sieve_extension *const *exts;
 				unsigned int ext_count, i;
 
 				valdtr->finished_require = TRUE;
 
+				/* Load implicit extensions */
+				exts = sieve_extensions_get_all(valdtr->svinst, &ext_count);
+				for (i = 0; i < ext_count; i++) {
+					if ( exts[i]->implicit ) {
+						(void)sieve_validator_extension_load
+							(valdtr, NULL, NULL, exts[i]);
+					}
+				}
+
 				/* Validate all 'require'd extensions */
 				extrs = array_get(&valdtr->extensions, &ext_count);
 				for ( i = 0; i < ext_count; i++ ) {

src/lib-sieve/sieve-validator.h

@@ -138,7 +138,8 @@ struct sieve_validator_extension {
 
 bool sieve_validator_extension_load
 	(struct sieve_validator *valdtr, struct sieve_command *cmd,
-		struct sieve_ast_argument *ext_arg, const struct sieve_extension *ext);
+		struct sieve_ast_argument *ext_arg, const struct sieve_extension *ext)
+	ATTR_NULL(2, 3);
 const struct sieve_extension *sieve_validator_extension_load_by_name
 	(struct sieve_validator *valdtr, struct sieve_command *cmd,
 		struct sieve_ast_argument *ext_arg, const char *ext_name);

src/lib-sieve/sieve.c

@@ -132,7 +132,7 @@ void sieve_deinit(struct sieve_instance **_svinst)
 void sieve_set_extensions
 (struct sieve_instance *svinst, const char *extensions)
 {
-	sieve_extensions_set_string(svinst, extensions, FALSE);
+	sieve_extensions_set_string(svinst, extensions, FALSE, FALSE);
 }
 
 const char *sieve_get_capabilities