param: abstract 'struct command' so param doesn't need to access it.

I want to use param functions in plugins, and they don't have struct
command.

I had to use a special arg to param() for check to flag it as allowing
extra parameters, rather than adding a one-use accessor.

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

common/Makefile

@@ -52,7 +52,7 @@ COMMON_SRC_NOGEN :=				\
 
 COMMON_SRC_GEN := common/gen_status_wire.c common/gen_peer_status_wire.c
 
-COMMON_HEADERS_NOGEN := $(COMMON_SRC_NOGEN:.c=.h) common/overflows.h common/htlc.h common/status_levels.h
+COMMON_HEADERS_NOGEN := $(COMMON_SRC_NOGEN:.c=.h) common/overflows.h common/htlc.h common/status_levels.h common/json_command.h
 COMMON_HEADERS_GEN := common/gen_htlc_state_names.h common/gen_status_wire.h common/gen_peer_status_wire.h
 
 COMMON_HEADERS := $(COMMON_HEADERS_GEN) $(COMMON_HEADERS_NOGEN)

common/json_command.h

@@ -0,0 +1,24 @@
+/* These functions must be supplied by any binary linking with common/param
+ * so it can fail commands. */
+#ifndef LIGHTNING_COMMON_JSON_COMMAND_H
+#define LIGHTNING_COMMON_JSON_COMMAND_H
+#include "config.h"
+#include <ccan/compiler/compiler.h>
+#include <stdbool.h>
+
+struct command;
+
+/* Caller supplied this: param assumes it can call it. */
+void PRINTF_FMT(3, 4) command_fail(struct command *cmd, int code,
+				   const char *fmt, ...);
+
+/* Also caller supplied: is this invoked simply to get usage? */
+bool command_usage_only(const struct command *cmd);
+
+/* If so, this is called. */
+void command_set_usage(struct command *cmd, const char *usage);
+
+/* Also caller supplied: is this invoked simply to check parameters? */
+bool command_check_only(const struct command *cmd);
+
+#endif /* LIGHTNING_COMMON_JSON_COMMAND_H */

lightningd/jsonrpc.c

@@ -23,6 +23,7 @@
 #include <ccan/str/hex/hex.h>
 #include <ccan/tal/str/str.h>
 #include <common/bech32.h>
+#include <common/json_command.h>
 #include <common/memleak.h>
 #include <common/timeout.h>
 #include <common/version.h>
@@ -551,7 +552,6 @@ 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);
 
@@ -776,6 +776,21 @@ struct jsonrpc *jsonrpc_new(const tal_t *ctx, struct lightningd *ld)
 	return jsonrpc;
 }
 
+bool command_usage_only(const struct command *cmd)
+{
+	return cmd->mode == CMD_USAGE;
+}
+
+void command_set_usage(struct command *cmd, const char *usage)
+{
+	cmd->usage = usage;
+}
+
+bool command_check_only(const struct command *cmd)
+{
+	return cmd->mode == CMD_CHECK;
+}
+
 void jsonrpc_listen(struct jsonrpc *jsonrpc, struct lightningd *ld)
 {
 	struct sockaddr_un addr;
@@ -980,11 +995,11 @@ static void json_check(struct command *cmd,
 		mod_params = NULL;
 	} else {
 		mod_params = json_tok_copy(cmd, params);
-		cmd->allow_unused = true;
 	}
 
 	if (!param(cmd, buffer, mod_params,
 		   p_req("command_to_check", json_tok_command, &name_tok),
+		   p_opt_any(),
 		   NULL))
 		return;
 
@@ -995,7 +1010,6 @@ static void json_check(struct command *cmd,
 	json_tok_remove(&mod_params, (jsmntok_t *)name_tok, 1);
 
 	cmd->mode = CMD_CHECK;
-	cmd->allow_unused = false;
 	/* FIXME(wythe): Maybe change "ok" to "failed" since that's really what
 	 * we're after and would be more clear. */
 	ok = true;

lightningd/jsonrpc.h

@@ -38,8 +38,6 @@ 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

@@ -1,5 +1,6 @@
 #include <ccan/asort/asort.h>
 #include <ccan/tal/str/str.h>
+#include <common/json_command.h>
 #include <common/utils.h>
 #include <lightningd/json.h>
 #include <lightningd/jsonrpc.h>
@@ -63,7 +64,8 @@ static bool post_check(struct command *cmd, struct param *params)
 static bool parse_by_position(struct command *cmd,
 			      struct param *params,
 			      const char *buffer,
-			      const jsmntok_t tokens[])
+			      const jsmntok_t tokens[],
+			      bool allow_extra)
 {
 	const jsmntok_t *tok = tokens + 1;
 	const jsmntok_t *end = json_next(tokens);
@@ -79,7 +81,7 @@ static bool parse_by_position(struct command *cmd,
 	}
 
 	/* check for unexpected trailing params */
-	if (!cmd->allow_unused && tok != end) {
+	if (!allow_extra && tok != end) {
 		command_fail(cmd, JSONRPC2_INVALID_PARAMS,
 			     "too many parameters:"
 			     " got %u, expected %zu",
@@ -108,7 +110,8 @@ static struct param *find_param(struct param *params, const char *start,
 static bool parse_by_name(struct command *cmd,
 			  struct param *params,
 			  const char *buffer,
-			  const jsmntok_t tokens[])
+			  const jsmntok_t tokens[],
+			  bool allow_extra)
 {
 	const jsmntok_t *first = tokens + 1;
 	const jsmntok_t *last = json_next(tokens);
@@ -117,7 +120,7 @@ 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) {
+			if (!allow_extra) {
 				command_fail(cmd, JSONRPC2_INVALID_PARAMS,
 					     "unknown parameter: '%.*s'",
 					     first->end - first->start,
@@ -239,7 +242,8 @@ static char *param_usage(const tal_t *ctx,
 
 static bool param_arr(struct command *cmd, const char *buffer,
 		      const jsmntok_t tokens[],
-		      struct param *params)
+		      struct param *params,
+		      bool allow_extra)
 {
 #if DEVELOPER
 	if (!check_params(params)) {
@@ -248,9 +252,9 @@ static bool param_arr(struct command *cmd, const char *buffer,
 	}
 #endif
 	if (tokens->type == JSMN_ARRAY)
-		return parse_by_position(cmd, params, buffer, tokens);
+		return parse_by_position(cmd, params, buffer, tokens, allow_extra);
 	else if (tokens->type == JSMN_OBJECT)
-		return parse_by_name(cmd, params, buffer, tokens);
+		return parse_by_name(cmd, params, buffer, tokens, allow_extra);
 
 	command_fail(cmd, JSONRPC2_INVALID_PARAMS,
 		     "Expected array or object for params");
@@ -263,12 +267,17 @@ bool param(struct command *cmd, const char *buffer,
 	struct param *params = tal_arr(cmd, struct param, 0);
 	const char *name;
 	va_list ap;
+	bool allow_extra = false;
 
 	va_start(ap, tokens);
 	while ((name = va_arg(ap, const char *)) != NULL) {
 		bool required = va_arg(ap, int);
 		param_cbx cbx = va_arg(ap, param_cbx);
 		void *arg = va_arg(ap, void *);
+		if (streq(name, "")) {
+			allow_extra = true;
+			continue;
+		}
 		if  (!param_add(&params, name, required, cbx, arg)) {
 			command_fail(cmd, PARAM_DEV_ERROR,
 				     "developer error: param_add %s", name);
@@ -278,14 +287,13 @@ bool param(struct command *cmd, const char *buffer,
 	}
 	va_end(ap);
 
-	if (cmd->mode == CMD_USAGE) {
-		cmd->usage = param_usage(cmd, params);
+	if (command_usage_only(cmd)) {
+		command_set_usage(cmd, param_usage(cmd, params));
 		return false;
 	}
 
-	/* Always return false for CMD_USAGE and CMD_CHECK, signaling the caller
-	 * to return immediately.  For CMD_NORMAL, return true if all parameters
-	 * are valid.
-	 */
-	return param_arr(cmd, buffer, tokens, params) && cmd->mode == CMD_NORMAL;
+	/* Always return false if we're simply checking command parameters;
+	 * normally this returns true if all parameters are valid. */
+	return param_arr(cmd, buffer, tokens, params, allow_extra)
+		&& !command_check_only(cmd);
 }

lightningd/param.h

@@ -90,4 +90,6 @@ typedef bool(*param_cbx)(struct command *cmd,
 				   (const jsmntok_t *)NULL,	    \
 				   (arg)) == true); })
 
+/* Special flag for 'check' which allows any parameters. */
+#define p_opt_any() "", false, NULL, NULL
 #endif /* LIGHTNING_LIGHTNINGD_PARAM_H */

lightningd/test/run-param.c

@@ -48,6 +48,21 @@ bool json_feerate_estimate(struct command *cmd UNNEEDED,
 { fprintf(stderr, "json_feerate_estimate called!\n"); abort(); }
 /* AUTOGENERATED MOCKS END */
 
+void command_set_usage(struct command *cmd, const char *usage)
+{
+	cmd->usage = usage;
+}
+
+bool command_usage_only(const struct command *cmd)
+{
+	return cmd->mode == CMD_USAGE;
+}
+
+bool command_check_only(const struct command *cmd)
+{
+	return cmd->mode == CMD_CHECK;
+}
+
 struct json {
 	jsmntok_t *toks;
 	char *buffer;
@@ -353,7 +368,7 @@ static void five_hundred_params(void)
 
 	/* first test object version */
 	struct json *j = json_parse(params, obj);
-	assert(param_arr(cmd, j->buffer, j->toks, params));
+	assert(param_arr(cmd, j->buffer, j->toks, params, false));
 	for (int i = 0; i < tal_count(ints); ++i) {
 		assert(ints[i]);
 		assert(*ints[i] == i);
@@ -362,7 +377,7 @@ static void five_hundred_params(void)
 
 	/* now test array */
 	j = json_parse(params, arr);
-	assert(param_arr(cmd, j->buffer, j->toks, params));
+	assert(param_arr(cmd, j->buffer, j->toks, params, false));
 	for (int i = 0; i < tal_count(ints); ++i) {
 		assert(*ints[i] == i);
 	}
@@ -563,7 +578,6 @@ int main(void)
 	setup_tmpctx();
 	cmd = tal(tmpctx, struct command);
 	cmd->mode = CMD_NORMAL;
-	cmd->allow_unused = false;
 	fail_msg = tal_arr(cmd, char, 10000);
 
 	zero_params();