jsonrpc: probe sites for usage information once, at start.

We store it in a strmap.  This means we call the jsonrpc handler earlier,
so all callers need to call param() before they do anything else; only
json_listaddrs and json_help needed fixing.

Plugins still use '[usage]' for now.

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

lightningd/jsonrpc.c

@@ -21,6 +21,7 @@
 #include <ccan/err/err.h>
 #include <ccan/io/io.h>
 #include <ccan/str/hex/hex.h>
+#include <ccan/strmap/strmap.h>
 #include <ccan/tal/str/str.h>
 #include <common/bech32.h>
 #include <common/json_command.h>
@@ -38,6 +39,7 @@
 #include <lightningd/json.h>
 #include <lightningd/jsonrpc.h>
 #include <lightningd/log.h>
+#include <lightningd/memdump.h>
 #include <lightningd/options.h>
 #include <stdio.h>
 #include <sys/socket.h>
@@ -106,6 +108,10 @@ struct jsonrpc {
 	struct io_listener *rpc_listener;
 	struct json_command **commands;
 	struct log *log;
+
+	/* Map from json command names to usage strings: we don't put this inside
+	 * struct json_command as it's good practice to have those const. */
+	STRMAP(const char *) usagemap;
 };
 
 /* The command itself usually owns the stream, because jcon may get closed.
@@ -304,10 +310,11 @@ static void json_add_help_command(struct command *cmd,
 				  struct json_command *json_command)
 {
 	char *usage;
-	cmd->mode = CMD_USAGE;
-	json_command->dispatch(cmd, NULL, NULL, NULL);
-	usage = tal_fmt(cmd, "%s %s", json_command->name, cmd->usage);
 
+	usage = tal_fmt(cmd, "%s %s",
+			json_command->name,
+			strmap_get(&cmd->ld->jsonrpc->usagemap,
+				   json_command->name));
 	json_object_start(response, NULL);
 
 	json_add_string(response, "command", usage);
@@ -347,7 +354,7 @@ static struct command_result *json_help(struct command *cmd,
 {
 	struct json_stream *response;
 	const jsmntok_t *cmdtok;
-	struct json_command **commands = cmd->ld->jsonrpc->commands;
+	struct json_command **commands;
 	const struct json_command *one_cmd;
 
 	if (!param(cmd, buffer, params,
@@ -355,6 +362,7 @@ static struct command_result *json_help(struct command *cmd,
 		   NULL))
 		return command_param_failed();
 
+	commands = cmd->ld->jsonrpc->commands;
 	if (cmdtok) {
 		one_cmd = find_command(commands, buffer, cmdtok);
 		if (!one_cmd)
@@ -771,6 +779,7 @@ static struct io_plan *incoming_jcon_connected(struct io_conn *conn,
 
 static void destroy_json_command(struct json_command *command, struct jsonrpc *rpc)
 {
+	strmap_del(&rpc->usagemap, command->name, NULL);
 	for (size_t i = 0; i < tal_count(rpc->commands); i++) {
 		if (rpc->commands[i] == command) {
 			tal_arr_remove(&rpc->commands, i);
@@ -780,9 +789,7 @@ static void destroy_json_command(struct json_command *command, struct jsonrpc *r
 	abort();
 }
 
-/* For built-in ones, they're not tal objects, so no destructor */
-static bool jsonrpc_command_add_perm(struct jsonrpc *rpc,
-				     struct json_command *command)
+static bool command_add(struct jsonrpc *rpc, struct json_command *command)
 {
 	size_t count = tal_count(rpc->commands);
 
@@ -795,23 +802,54 @@ static bool jsonrpc_command_add_perm(struct jsonrpc *rpc,
 	return true;
 }
 
-bool jsonrpc_command_add(struct jsonrpc *rpc, struct json_command *command)
+/* Built-in commands get called to construct usage string via param() */
+static void setup_command_usage(struct lightningd *ld,
+				struct json_command *command)
 {
-	if (!jsonrpc_command_add_perm(rpc, command))
+	const struct command_result *res;
+	struct command *dummy;
+
+	/* Call it with minimal cmd, to fill out usagemap */
+	dummy = tal(tmpctx, struct command);
+	dummy->mode = CMD_USAGE;
+	dummy->ld = ld;
+	dummy->json_cmd = command;
+	res = command->dispatch(dummy, NULL, NULL, NULL);
+	assert(res == &param_failed);
+	assert(strmap_get(&ld->jsonrpc->usagemap, command->name));
+}
+
+bool jsonrpc_command_add(struct jsonrpc *rpc, struct json_command *command,
+			 const char *usage TAKES)
+{
+	if (!command_add(rpc, command))
 		return false;
+	usage = tal_strdup(command, usage);
+	strmap_add(&rpc->usagemap, command->name, usage);
 	tal_add_destructor2(command, destroy_json_command, rpc);
 	return true;
 }
 
+static bool jsonrpc_command_add_perm(struct lightningd *ld,
+				     struct jsonrpc *rpc,
+				     struct json_command *command)
+{
+	if (!command_add(rpc, command))
+		return false;
+	setup_command_usage(ld, command);
+	return true;
+}
+
 void jsonrpc_setup(struct lightningd *ld)
 {
 	struct json_command **commands = get_cmdlist();
 
 	ld->jsonrpc = tal(ld, struct jsonrpc);
+	strmap_init(&ld->jsonrpc->usagemap);
 	ld->jsonrpc->commands = tal_arr(ld->jsonrpc, struct json_command *, 0);
 	ld->jsonrpc->log = new_log(ld->jsonrpc, ld->log_book, "jsonrpc");
 	for (size_t i=0; i<num_cmdlist; i++) {
-		if (!jsonrpc_command_add_perm(ld->jsonrpc, commands[i]))
+		if (!jsonrpc_command_add_perm(ld, ld->jsonrpc, commands[i]))
 			fatal("Cannot add duplicate command %s",
 			      commands[i]->name);
 	}
@@ -823,9 +861,11 @@ bool command_usage_only(const struct command *cmd)
 	return cmd->mode == CMD_USAGE;
 }
 
-void command_set_usage(struct command *cmd, const char *usage)
+void command_set_usage(struct command *cmd, const char *usage TAKES)
 {
-	cmd->usage = usage;
+	usage = tal_strdup(cmd->ld, usage);
+	if (!strmap_add(&cmd->ld->jsonrpc->usagemap, cmd->json_cmd->name, usage))
+		fatal("Two usages for command %s?", cmd->json_cmd->name);
 }
 
 bool command_check_only(const struct command *cmd)
@@ -1141,3 +1181,11 @@ static const struct json_command check_command = {
 };
 
 AUTODATA(json_command, &check_command);
+
+#if DEVELOPER
+void jsonrpc_remove_memleak(struct htable *memtable,
+			    const struct jsonrpc *jsonrpc)
+{
+	memleak_remove_strmap(memtable, &jsonrpc->usagemap);
+}
+#endif /* DEVELOPER */

lightningd/jsonrpc.h

@@ -37,8 +37,6 @@ struct command {
 	bool pending;
 	/* Tell param() how to process the command */
 	enum command_mode mode;
-	/* This is created if mode is CMD_USAGE */
-	const char *usage;
 	/* Have we started a json stream already?  For debugging. */
 	bool have_json_stream;
 };
@@ -175,7 +173,8 @@ void jsonrpc_listen(struct jsonrpc *rpc, struct lightningd *ld);
  *
  * Free @command to remove it.
  */
-bool jsonrpc_command_add(struct jsonrpc *rpc, struct json_command *command);
+bool jsonrpc_command_add(struct jsonrpc *rpc, struct json_command *command,
+			 const char *usage TAKES);
 
 /**
  * Begin a JSON-RPC notification with the specified topic.
@@ -208,4 +207,13 @@ struct jsonrpc_request *jsonrpc_request_start_(
 void jsonrpc_request_end(struct jsonrpc_request *request);
 
 AUTODATA_TYPE(json_command, struct json_command);
+
+#if DEVELOPER
+struct htable;
+struct jsonrpc;
+
+void jsonrpc_remove_memleak(struct htable *memtable,
+			    const struct jsonrpc *jsonrpc);
+#endif /* DEVELOPER */
+
 #endif /* LIGHTNING_LIGHTNINGD_JSONRPC_H */

lightningd/memdump.c

@@ -154,6 +154,7 @@ static void scan_mem(struct command *cmd,
 	memleak_remove_htable(memtable, &ld->topology->txowatches.raw);
 	memleak_remove_htable(memtable, &ld->htlcs_in.raw);
 	memleak_remove_htable(memtable, &ld->htlcs_out.raw);
+	jsonrpc_remove_memleak(memtable, ld->jsonrpc);
 
 	/* Now delete ld and those which it has pointers to. */
 	memleak_remove_referenced(memtable, ld);

lightningd/plugin.c

@@ -610,11 +610,8 @@ static struct command_result *plugin_rpcmethod_dispatch(struct command *cmd,
 	struct jsonrpc_request *req;
 	char id[STR_MAX_CHARS(u64)];
 
-	if (cmd->mode == CMD_USAGE || cmd->mode == CMD_CHECK) {
-		/* FIXME! */
-		cmd->usage = "[params]";
+	if (cmd->mode == CMD_CHECK)
 		return command_param_failed();
-	}
 
 	plugin = find_plugin_for_command(cmd);
 
@@ -675,7 +672,9 @@ static bool plugin_rpcmethod_add(struct plugin *plugin,
 
 	cmd->deprecated = false;
 	cmd->dispatch = plugin_rpcmethod_dispatch;
-	if (!jsonrpc_command_add(plugin->plugins->ld->jsonrpc, cmd)) {
+	if (!jsonrpc_command_add(plugin->plugins->ld->jsonrpc, cmd,
+				 /* FIXME */
+				 "[params]")) {
 		log_broken(plugin->log,
 			   "Could not register method \"%s\", a method with "
 			   "that name is already registered",

lightningd/test/run-jsonrpc.c

@@ -40,6 +40,9 @@ void log_io(struct log *log UNNEEDED, enum log_level dir UNNEEDED, const char *c
 /* Generated stub for log_prefix */
 const char *log_prefix(const struct log *log UNNEEDED)
 { fprintf(stderr, "log_prefix called!\n"); abort(); }
+/* Generated stub for memleak_remove_strmap_ */
+void memleak_remove_strmap_(struct htable *memtable UNNEEDED, const struct strmap *m UNNEEDED)
+{ fprintf(stderr, "memleak_remove_strmap_ called!\n"); abort(); }
 /* Generated stub for new_log */
 struct log *new_log(const tal_t *ctx UNNEEDED, struct log_book *record UNNEEDED, const char *fmt UNNEEDED, ...)
 { fprintf(stderr, "new_log called!\n"); abort(); }

wallet/walletrpc.c

@@ -332,12 +332,15 @@ static struct command_result *json_listaddrs(struct command *cmd,
 	u64 *bip32_max_index;
 
 	if (!param(cmd, buffer, params,
-		   p_opt_def("bip32_max_index", param_u64, &bip32_max_index,
-				 db_get_intvar(cmd->ld->wallet->db,
-				 "bip32_max_index", 0)),
+		   p_opt("bip32_max_index", param_u64, &bip32_max_index),
 		   NULL))
 		return command_param_failed();
 
+	if (!bip32_max_index) {
+		bip32_max_index = tal(cmd, u64);
+		*bip32_max_index = db_get_intvar(cmd->ld->wallet->db,
+						 "bip32_max_index", 0);
+	}
 	response = json_stream_success(cmd);
 	json_object_start(response, NULL);
 	json_array_start(response, "addresses");