param: add support for unused parameters

We can now set a flag to have param() ignore unexpected parameters.
Normally unexpected parameters are considered errors.
Needed by the check command.

Signed-off-by: Mark Beckwith <wythe@intrig.com>

lightningd/jsonrpc.c

@@ -537,6 +537,7 @@ static void parse_request(struct json_connection *jcon, const jsmntok_t tok[])
 			    json_tok_len(id));
 	c->mode = CMD_NORMAL;
 	c->ok = NULL;
+	c->allow_unused = false;
 	list_add_tail(&jcon->commands, &c->list);
 	tal_add_destructor(c, destroy_command);
 

lightningd/jsonrpc.h

@@ -36,6 +36,8 @@ struct command {
 	/* This is created if mode is CMD_USAGE */
 	const char *usage;
 	bool *ok;
+	/* Do not report unused parameters as errors (default false). */
+	bool allow_unused;
 	/* Have we started a json stream already?  For debugging. */
 	bool have_json_stream;
 };

lightningd/param.c

@@ -79,7 +79,7 @@ static bool parse_by_position(struct command *cmd,
 	}
 
 	/* check for unexpected trailing params */
-	if (tok != end) {
+	if (!cmd->allow_unused && tok != end) {
 		command_fail(cmd, JSONRPC2_INVALID_PARAMS,
 			     "too many parameters:"
 			     " got %u, expected %zu",
@@ -117,13 +117,14 @@ static bool parse_by_name(struct command *cmd,
 		struct param *p = find_param(params, buffer + first->start,
 					     first->end - first->start);
 		if (!p) {
+			if (!cmd->allow_unused) {
 				command_fail(cmd, JSONRPC2_INVALID_PARAMS,
 					     "unknown parameter: '%.*s'",
 					     first->end - first->start,
 					     buffer + first->start);
 				return false;
 			}
-
+		} else {
 			if (p->is_set) {
 				command_fail(cmd, JSONRPC2_INVALID_PARAMS,
 					     "duplicate json names: '%s'", p->name);
@@ -132,6 +133,7 @@ static bool parse_by_name(struct command *cmd,
 
 			if (!make_callback(cmd, p, buffer, first + 1))
 				return false;
+		}
 		first = json_next(first + 1);
 	}
 	return post_check(cmd, params);