libplugin: add support for before and after deps on hooks.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

plugins/libplugin.c

@@ -628,8 +628,25 @@ handle_getmanifest(struct command *getmanifest_cmd,
 	json_array_end(params);
 
 	json_array_start(params, "hooks");
-	for (size_t i = 0; i < p->num_hook_subs; i++)
-		json_add_string(params, NULL, p->hook_subs[i].name);
+	for (size_t i = 0; i < p->num_hook_subs; i++) {
+		json_object_start(params, NULL);
+		json_add_string(params, "name", p->hook_subs[i].name);
+		if (p->hook_subs[i].before) {
+			json_array_start(params, "before");
+			for (size_t j = 0; p->hook_subs[i].before[j]; j++)
+				json_add_string(params, NULL,
+						p->hook_subs[i].before[j]);
+			json_array_end(params);
+		}
+		if (p->hook_subs[i].after) {
+			json_array_start(params, "after");
+			for (size_t j = 0; p->hook_subs[i].after[j]; j++)
+				json_add_string(params, NULL,
+						p->hook_subs[i].after[j]);
+			json_array_end(params);
+		}
+		json_object_end(params);
+	}
 	json_array_end(params);
 
 	if (p->our_features != NULL) {

plugins/libplugin.h

@@ -93,6 +93,8 @@ struct plugin_hook {
 	struct command_result *(*handle)(struct command *cmd,
 	                                 const char *buf,
 	                                 const jsmntok_t *params);
+	/* If non-NULL, these are NULL-terminated arrays of deps */
+	const char **before, **after;
 };
 
 /* Return the feature set of the current lightning node */

tests/plugins/test_libplugin.c

@@ -118,9 +118,14 @@ static const struct plugin_command commands[] = { {
 	}
 };
 
+static const char *before[] = { "dummy", NULL };
+static const char *after[] = { "dummy", NULL };
+
 static const struct plugin_hook hooks[] = { {
 		"peer_connected",
 		json_peer_connected,
+		before,
+		after
 	}
 };