libplugin: allow display of default values.

This means we can see the values in listconfigs, even if we haven't set
them yet.

In particular, we now see the following:

* autoclean-cycle.value_int=3600
* bitcoin-rpcclienttimeout.value_int=60
* bitcoin-retry-timeout.value_int=60
* funder-max-their-funding.value_str=4294967295sat
* funder-per-channel-min.value_str=10000sat
* funder-reserve-tank.value_str=0sat
* funder-fund-probability.value_int=100

Changelog-Changed: plugins: libplugin now shows plugin option default values (where they're non-trivial)
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

plugins/autoclean.c

@@ -581,21 +581,29 @@ static const char *init(struct plugin *p,
 
 static char *cycle_seconds_option(struct plugin *plugin, const char *arg,
 				  bool check_only,
-				  void *unused)
+				  u64 *cycle_seconds)
 {
-	char *problem = u64_option(plugin, arg, check_only, &cycle_seconds);
+	char *problem = u64_option(plugin, arg, check_only, cycle_seconds);
 	if (problem || check_only)
 		return problem;
 
 	/* If timer is not running right now, reset it to new cycle_seconds */
 	if (cleantimer) {
 		tal_free(cleantimer);
-		cleantimer = plugin_timer(plugin, time_from_sec(cycle_seconds),
+		cleantimer = plugin_timer(plugin, time_from_sec(*cycle_seconds),
 					  do_clean_timer, NULL);
 	}
 	return NULL;
 }
 
+static bool u64_jsonfmt_unless_zero(struct plugin *plugin,
+				    struct json_stream *js, const char *fieldname, u64 *i)
+{
+	if (!*i)
+		return false;
+	return u64_jsonfmt(plugin, js, fieldname, i);
+}
+
 static const struct plugin_command commands[] = { {
 	"autocleaninvoice",
 	"payment",
@@ -628,30 +636,37 @@ int main(int argc, char *argv[])
 					  "int",
 					  "Perform cleanup every"
 					  " given seconds",
-					  cycle_seconds_option, NULL),
+					  cycle_seconds_option, u64_jsonfmt,
+					  &cycle_seconds),
 		    plugin_option_dynamic("autoclean-succeededforwards-age",
 					  "int",
 					  "How old do successful forwards have to be before deletion (0 = never)",
-					  u64_option, &timer_cinfo.subsystem_age[SUCCEEDEDFORWARDS]),
+					  u64_option, u64_jsonfmt_unless_zero,
+					  &timer_cinfo.subsystem_age[SUCCEEDEDFORWARDS]),
 		    plugin_option_dynamic("autoclean-failedforwards-age",
 					  "int",
 					  "How old do failed forwards have to be before deletion (0 = never)",
-					  u64_option, &timer_cinfo.subsystem_age[FAILEDFORWARDS]),
+					  u64_option, u64_jsonfmt_unless_zero,
+					  &timer_cinfo.subsystem_age[FAILEDFORWARDS]),
 		    plugin_option_dynamic("autoclean-succeededpays-age",
 					  "int",
 					  "How old do successful pays have to be before deletion (0 = never)",
-					  u64_option, &timer_cinfo.subsystem_age[SUCCEEDEDPAYS]),
+					  u64_option, u64_jsonfmt_unless_zero,
+					  &timer_cinfo.subsystem_age[SUCCEEDEDPAYS]),
 		    plugin_option_dynamic("autoclean-failedpays-age",
 					  "int",
 					  "How old do failed pays have to be before deletion (0 = never)",
-					  u64_option, &timer_cinfo.subsystem_age[FAILEDPAYS]),
+					  u64_option, u64_jsonfmt_unless_zero,
+					  &timer_cinfo.subsystem_age[FAILEDPAYS]),
 		    plugin_option_dynamic("autoclean-paidinvoices-age",
 					  "int",
 					  "How old do paid invoices have to be before deletion (0 = never)",
-					  u64_option, &timer_cinfo.subsystem_age[PAIDINVOICES]),
+					  u64_option, u64_jsonfmt_unless_zero,
+					  &timer_cinfo.subsystem_age[PAIDINVOICES]),
 		    plugin_option_dynamic("autoclean-expiredinvoices-age",
 					  "int",
 					  "How old do expired invoices have to be before deletion (0 = never)",
-					  u64_option, &timer_cinfo.subsystem_age[EXPIREDINVOICES]),
+					  u64_option, u64_jsonfmt_unless_zero,
+					  &timer_cinfo.subsystem_age[EXPIREDINVOICES]),
 		    NULL);
 }

plugins/bcli.c

@@ -1257,39 +1257,39 @@ int main(int argc, char *argv[])
 		    plugin_option("bitcoin-datadir",
 				  "string",
 				  "-datadir arg for bitcoin-cli",
-				  charp_option, &bitcoind->datadir),
+				  charp_option, NULL, &bitcoind->datadir),
 		    plugin_option("bitcoin-cli",
 				  "string",
 				  "bitcoin-cli pathname",
-				  charp_option, &bitcoind->cli),
+				  charp_option, NULL, &bitcoind->cli),
 		    plugin_option("bitcoin-rpcuser",
 				  "string",
 				  "bitcoind RPC username",
-				  charp_option, &bitcoind->rpcuser),
+				  charp_option, NULL, &bitcoind->rpcuser),
 		    plugin_option("bitcoin-rpcpassword",
 				  "string",
 				  "bitcoind RPC password",
-				  charp_option, &bitcoind->rpcpass),
+				  charp_option, NULL, &bitcoind->rpcpass),
 		    plugin_option("bitcoin-rpcconnect",
 				  "string",
 				  "bitcoind RPC host to connect to",
-				  charp_option, &bitcoind->rpcconnect),
+				  charp_option, NULL, &bitcoind->rpcconnect),
 		    plugin_option("bitcoin-rpcport",
 				  "int",
 				  "bitcoind RPC host's port",
-				  charp_option, &bitcoind->rpcport),
+				  charp_option, NULL, &bitcoind->rpcport),
 		    plugin_option("bitcoin-rpcclienttimeout",
 				  "int",
 				  "bitcoind RPC timeout in seconds during HTTP requests",
-				  u64_option, &bitcoind->rpcclienttimeout),
+				  u64_option, u64_jsonfmt, &bitcoind->rpcclienttimeout),
 		    plugin_option("bitcoin-retry-timeout",
 				  "int",
 				  "how long to keep retrying to contact bitcoind"
 				  " before fatally exiting",
-				  u64_option, &bitcoind->retry_timeout),
+				  u64_option, u64_jsonfmt, &bitcoind->retry_timeout),
 		    plugin_option_dev("dev-no-fake-fees",
 				      "bool",
 				      "Suppress fee faking for regtest",
-				      bool_option, &bitcoind->dev_no_fake_fees),
+				      bool_option, NULL, &bitcoind->dev_no_fake_fees),
 		    NULL);
 }

plugins/bkpr/bookkeeper.c

@@ -1839,11 +1839,11 @@ int main(int argc, char *argv[])
 		    plugin_option("bookkeeper-dir",
 				  "string",
 				  "Location for bookkeeper records.",
-				  charp_option, &datadir),
+				  charp_option, NULL, &datadir),
 		    plugin_option("bookkeeper-db",
 				  "string",
 				  "Location of the bookkeeper database",
-				  charp_option, &db_dsn),
+				  charp_option, NULL, &db_dsn),
 		    NULL);
 
 	return 0;

plugins/fetchinvoice.c

@@ -1500,6 +1500,6 @@ int main(int argc, char *argv[])
 		    NULL, 0,
 		    plugin_option("fetchinvoice-noconnect", "flag",
 				  "Don't try to connect directly to fetch an invoice.",
-				  flag_option, &disable_connect),
+				  flag_option, flag_jsonfmt, &disable_connect),
 		    NULL);
 }

plugins/funder.c

@@ -1593,6 +1593,17 @@ static char *amount_option(struct plugin *plugin, const char *arg, bool check_on
 	return NULL;
 }
 
+static bool jsonfmt_amount_sat(struct plugin *plugin,
+			       struct json_stream *js,
+			       const char *fieldname,
+			       struct amount_sat *sats)
+{
+	/* We do not expose raw numbers for sats fields: raw numbers
+	 * in our interface means MSAT! */
+	json_add_str_fmt(js, fieldname, "%"PRIu64"sat", sats->satoshis /* Raw: fmt */);
+	return true;
+}
+
 static char *option_lease_fee_base(struct plugin *plugin, const char *arg,
 				   bool check_only,
 				   struct funder_policy *policy)
@@ -1673,6 +1684,15 @@ static char *amount_sat_or_u64_option(struct plugin *plugin,
 	return NULL;
 }
 
+static bool jsonfmt_policy_mod(struct plugin *plugin,
+			       struct json_stream *js,
+			       const char *fieldname,
+			       u64 *amt)
+{
+	json_add_u64(js, fieldname, *amt);
+	return true;
+}
+
 int main(int argc, char **argv)
 {
 	setup_locale();
@@ -1690,93 +1710,111 @@ int main(int argc, char **argv)
 				  "string",
 				  "Policy to use for dual-funding requests."
 				  " [match, available, fixed]",
-				  funding_option, &current_policy->opt),
+				  funding_option,
+				  jsonfmt_funding_option,
+				  &current_policy->opt),
 		    plugin_option("funder-policy-mod",
 				  "string",
 				  "Percent to apply policy at"
 				  " (match/available); or amount to fund"
 				  " (fixed)",
 				  amount_sat_or_u64_option,
+				  jsonfmt_policy_mod,
 				  &current_policy->mod),
 		    plugin_option("funder-min-their-funding",
 				  "string",
 				  "Minimum funding peer must open with"
 				  " to activate our policy",
 				  amount_option,
+				  jsonfmt_amount_sat,
 				  &current_policy->min_their_funding),
 		    plugin_option("funder-max-their-funding",
 				  "string",
 				  "Maximum funding peer may open with"
 				  " to activate our policy",
 				  amount_option,
+				  jsonfmt_amount_sat,
 				  &current_policy->max_their_funding),
 		    plugin_option("funder-per-channel-min",
 				  "string",
 				  "Minimum funding we'll add to a channel."
 				  " If we can't meet this, we don't fund",
 				  amount_option,
+				  jsonfmt_amount_sat,
 				  &current_policy->per_channel_min),
 		    plugin_option("funder-per-channel-max",
 				  "string",
 				  "Maximum funding we'll add to a channel."
 				  " We cap all contributions to this",
 				  amount_option,
+				  jsonfmt_amount_sat,
 				  &current_policy->per_channel_max),
 		    plugin_option("funder-reserve-tank",
 				  "string",
 				  "Amount of funds we'll always leave"
 				  " available.",
 				  amount_option,
+				  jsonfmt_amount_sat,
 				  &current_policy->reserve_tank),
 		    plugin_option("funder-fuzz-percent",
 				  "int",
 				  "Percent to fuzz the policy contribution by."
 				  " Defaults to 0%. Max is 100%",
-				  u32_option,
+				  u32_option, u32_jsonfmt,
 				  &current_policy->fuzz_factor),
 		    plugin_option("funder-fund-probability",
 				  "int",
 				  "Percent of requests to consider."
 				  " Defaults to 100%. Setting to 0% will"
 				  " disable dual-funding",
-				  u32_option,
+				  u32_option, u32_jsonfmt,
 				  &current_policy->fund_probability),
 		    plugin_option("funder-lease-requests-only",
 				  "bool",
 				  "Only fund lease requests. Defaults to"
 				  " true if channel lease rates are"
 				  " being advertised",
-				  bool_option,
+				  bool_option, bool_jsonfmt,
 				  &current_policy->leases_only),
 		    plugin_option("lease-fee-base-sat",
 				  "string",
 				  "Channel lease rates, base fee for leased"
 				  " funds, in satoshi.",
-				  option_lease_fee_base, current_policy),
+				  option_lease_fee_base,
+				  NULL,
+				  current_policy),
 		    plugin_option("lease-fee-basis",
 				  "int",
 				  "Channel lease rates, basis charged"
 				  " for leased funds (per 10,000 satoshi.)",
-				  option_lease_fee_basis, current_policy),
+				  option_lease_fee_basis,
+				  NULL,
+				  current_policy),
 		    plugin_option("lease-funding-weight",
 				  "int",
 				  "Channel lease rates, weight"
 				  " we'll ask opening peer to pay for in"
 				  " funding transaction",
-				  option_lease_weight_max, current_policy),
+				  option_lease_weight_max,
+				  NULL,
+				  current_policy),
 		    plugin_option("channel-fee-max-base-msat",
 				  "string",
 				  "Channel lease rates, maximum channel"
 				  " fee base we'll charge for funds"
 				  " routed through a leased channel.",
-				  option_channel_base, current_policy),
+				  option_channel_base,
+				  NULL,
+				  current_policy),
 		    plugin_option("channel-fee-max-proportional-thousandths",
 				  "int",
 				  "Channel lease rates, maximum"
 				  " proportional fee (in thousandths, or ppt)"
 				  " we'll charge for funds routed through a"
 				  " leased channel. Note: 1ppt = 1,000ppm",
-				  option_channel_fee_proportional_thousandths_max, current_policy),
+				  option_channel_fee_proportional_thousandths_max,
+				  NULL,
+				  current_policy),
 		    NULL);
 
 	tal_free(current_policy);

plugins/funder_policy.c

@@ -2,6 +2,7 @@
 #include <assert.h>
 #include <bitcoin/script.h>
 #include <ccan/tal/str/str.h>
+#include <common/json_stream.h>
 #include <common/lease_rates.h>
 #include <common/pseudorand.h>
 #include <inttypes.h>
@@ -39,6 +40,15 @@ char *funding_option(struct plugin *plugin, const char *arg, bool check_only, en
 	return NULL;
 }
 
+bool jsonfmt_funding_option(struct plugin *plugin,
+			    struct json_stream *js,
+			    const char *fieldname,
+			    enum funder_opt *opt)
+{
+	json_add_string(js, fieldname, funder_opt_name(*opt));
+	return true;
+}
+
 const char *funder_policy_desc(const tal_t *ctx,
 			       const struct funder_policy *policy)
 {

plugins/funder_policy.h

@@ -97,6 +97,12 @@ const char *funder_policy_desc(const tal_t *ctx,
 char *funding_option(struct plugin *plugin, const char *arg, bool check_only,
 		     enum funder_opt *opt);
 
+/* Convert to JSON field */
+bool jsonfmt_funding_option(struct plugin *plugin,
+			    struct json_stream *js,
+			    const char *fieldname,
+			    enum funder_opt *opt);
+
 /* Check policy settings, return error if fails */
 char *funder_check_policy(const struct funder_policy *policy);
 #endif /* LIGHTNING_PLUGINS_FUNDER_POLICY_H */

plugins/libplugin.c

@@ -48,6 +48,10 @@ struct plugin_option {
 	 * for validity (but must not make any changes!) */
 	char *(*handle)(struct plugin *plugin, const char *str, bool check_only,
 			void *arg);
+	/* Print an option (used to show the default value, if returns true) */
+	bool (*jsonfmt)(struct plugin *plugin, struct json_stream *js, const char *fieldname,
+			void *arg);
+	/* Arg for handle and jsonfmt */
 	void *arg;
 	/* If true, this option requires --developer to be enabled */
 	bool dev_only;
@@ -1049,6 +1053,8 @@ handle_getmanifest(struct command *getmanifest_cmd,
 		json_add_string(params, "description", p->opts[i].description);
 		json_add_deprecated(params, "deprecated", p->opts[i].depr_start, p->opts[i].depr_end);
 		json_add_bool(params, "dynamic", p->opts[i].dynamic);
+		if (p->opts[i].jsonfmt)
+			p->opts[i].jsonfmt(p, params, "default", p->opts[i].arg);
 		json_object_end(params);
 	}
 	json_array_end(params);
@@ -1463,6 +1469,46 @@ char *charp_option(struct plugin *plugin, const char *arg, bool check_only, char
 	return NULL;
 }
 
+bool u64_jsonfmt(struct plugin *plugin, struct json_stream *js, const char *fieldname, u64 *i)
+{
+	json_add_u64(js, fieldname, *i);
+	return true;
+}
+
+bool u32_jsonfmt(struct plugin *plugin, struct json_stream *js, const char *fieldname, u32 *i)
+{
+	json_add_u32(js, fieldname, *i);
+	return true;
+}
+
+bool u16_jsonfmt(struct plugin *plugin, struct json_stream *js, const char *fieldname, u16 *i)
+{
+	json_add_u32(js, fieldname, *i);
+	return true;
+}
+
+bool bool_jsonfmt(struct plugin *plugin, struct json_stream *js, const char *fieldname, bool *i)
+{
+	json_add_bool(js, fieldname, *i);
+	return true;
+}
+
+bool charp_jsonfmt(struct plugin *plugin, struct json_stream *js, const char *fieldname, char **p)
+{
+	if (!*p)
+		return false;
+	json_add_string(js, fieldname, *p);
+	return true;
+}
+
+bool flag_jsonfmt(struct plugin *plugin, struct json_stream *js, const char *fieldname, bool *i)
+{
+	/* Don't print if the default (false) */
+	if (!*i)
+		return false;
+	return bool_jsonfmt(plugin, js, fieldname, i);
+}
+
 static void setup_command_usage(struct plugin *p)
 {
 	struct command *usage_cmd = tal(tmpctx, struct command);
@@ -2099,6 +2145,7 @@ static struct plugin *new_plugin(const tal_t *ctx,
 		o.type = va_arg(ap, const char *);
 		o.description = va_arg(ap, const char *);
 		o.handle = va_arg(ap, char *(*)(struct plugin *, const char *str, bool check_only, void *arg));
+		o.jsonfmt = va_arg(ap, bool (*)(struct plugin *, struct json_stream *, const char *, void *arg));
 		o.arg = va_arg(ap, void *);
 		o.dev_only = va_arg(ap, int); /* bool gets promoted! */
 		o.depr_start = va_arg(ap, const char *);

plugins/libplugin.h

@@ -416,11 +416,20 @@ static inline void *plugin_option_cb_check(char *(*set)(struct plugin *plugin,
 	return set;
 }
 
+/* Simply exists to check that `jsonfmt` to plugin_option* is correct type */
+static inline void *plugin_option_jsonfmt_check(bool (*jsonfmt)(struct plugin *,
+								struct json_stream *,
+								const char *,
+								void *))
+{
+	return jsonfmt;
+}
+
 /* Is --developer enabled? */
 bool plugin_developer_mode(const struct plugin *plugin);
 
 /* Macro to define arguments */
-#define plugin_option_(name, type, description, set, arg, dev_only, depr_start, depr_end, dynamic) \
+#define plugin_option_(name, type, description, set, jsonfmt, arg, dev_only, depr_start, depr_end, dynamic) \
 	(name),								\
 	(type),								\
 	(description),							\
@@ -428,23 +437,29 @@ bool plugin_developer_mode(const struct plugin *plugin);
 						   (set), (arg),	\
 						   struct plugin *,	\
 						   const char *, bool)),\
+	plugin_option_jsonfmt_check(typesafe_cb_preargs(bool, void *,	\
+							(jsonfmt), (arg), \
+							struct plugin *, \
+							struct json_stream *, \
+							const char *)),	\
 	(arg),								\
 	(dev_only),							\
 	(depr_start),							\
 	(depr_end),							\
 	(dynamic)
 
-#define plugin_option(name, type, description, set, arg) \
-	plugin_option_((name), (type), (description), (set), (arg), false, NULL, NULL, false)
+/* jsonfmt can be NULL, but then default won't be printed */
+#define plugin_option(name, type, description, set, jsonfmt, arg)	\
+	plugin_option_((name), (type), (description), (set), (jsonfmt), (arg), false, NULL, NULL, false)
 
-#define plugin_option_dev(name, type, description, set, arg) \
-	plugin_option_((name), (type), (description), (set), (arg), true, NULL, NULL, false)
+#define plugin_option_dev(name, type, description, set, jsonfmt, arg)	\
+	plugin_option_((name), (type), (description), (set), (jsonfmt), (arg), true, NULL, NULL, false)
 
-#define plugin_option_dynamic(name, type, description, set, arg) \
-	plugin_option_((name), (type), (description), (set), (arg), false, NULL, NULL, true)
+#define plugin_option_dynamic(name, type, description, set, jsonfmt, arg) \
+	plugin_option_((name), (type), (description), (set), (jsonfmt), (arg), false, NULL, NULL, true)
 
-#define plugin_option_deprecated(name, type, description, depr_start, depr_end, set, arg) \
-	plugin_option_((name), (type), (description), (set), (arg), false, (depr_start), (depr_end), false)
+#define plugin_option_deprecated(name, type, description, depr_start, depr_end, set, jsonfmt, arg) \
+	plugin_option_((name), (type), (description), (set), (jsonfmt), (arg), false, (depr_start), (depr_end), false)
 
 /* Standard helpers */
 char *u64_option(struct plugin *plugin, const char *arg, bool check_only, u64 *i);
@@ -454,6 +469,21 @@ char *bool_option(struct plugin *plugin, const char *arg, bool check_only, bool
 char *charp_option(struct plugin *plugin, const char *arg, bool check_only, char **p);
 char *flag_option(struct plugin *plugin, const char *arg, bool check_only, bool *i);
 
+bool u64_jsonfmt(struct plugin *plugin, struct json_stream *js, const char *fieldname,
+		 u64 *i);
+bool u32_jsonfmt(struct plugin *plugin, struct json_stream *js, const char *fieldname,
+		 u32 *i);
+bool u16_jsonfmt(struct plugin *plugin, struct json_stream *js, const char *fieldname,
+		 u16 *i);
+bool bool_jsonfmt(struct plugin *plugin, struct json_stream *js, const char *fieldname,
+		  bool *i);
+bool charp_jsonfmt(struct plugin *plugin, struct json_stream *js, const char *fieldname,
+		   char **p);
+
+/* Usually equivalent to NULL, since flag must default to false be useful! */
+bool flag_jsonfmt(struct plugin *plugin, struct json_stream *js, const char *fieldname,
+		  bool *i);
+
 /* The main plugin runner: append with 0 or more plugin_option(), then NULL. */
 void NORETURN LAST_ARG_NULL plugin_main(char *argv[],
 					const char *(*init)(struct plugin *p,

plugins/pay.c

@@ -1367,7 +1367,7 @@ int main(int argc, char *argv[])
 		    notification_topics, ARRAY_SIZE(notification_topics),
 		    plugin_option("disable-mpp", "flag",
 				  "Disable multi-part payments.",
-				  flag_option, &disablempp),
+				  flag_option, flag_jsonfmt, &disablempp),
 		    NULL);
 	io_poll_override(libplugin_pay_poll);
 }

plugins/renepay/main.c

@@ -427,10 +427,10 @@ int main(int argc, char *argv[])
 		/* notification topics */ NULL, 0,
 		plugin_option("renepay-debug-mcf", "flag",
 			"Enable renepay MCF debug info.",
-			flag_option, &pay_plugin->debug_mcf),
+			flag_option, NULL, &pay_plugin->debug_mcf),
 		plugin_option("renepay-debug-payflow", "flag",
 			"Enable renepay payment flows debug info.",
-			flag_option, &pay_plugin->debug_payflow),
+			flag_option, NULL, &pay_plugin->debug_payflow),
 		NULL);
 
 	return 0;

plugins/test/run-funder_policy.c

@@ -15,6 +15,11 @@ bool fromwire_channel_id(const u8 **cursor UNNEEDED, size_t *max UNNEEDED,
 /* Generated stub for fromwire_node_id */
 void fromwire_node_id(const u8 **cursor UNNEEDED, size_t *max UNNEEDED, struct node_id *id UNNEEDED)
 { fprintf(stderr, "fromwire_node_id called!\n"); abort(); }
+/* Generated stub for json_add_string */
+void json_add_string(struct json_stream *js UNNEEDED,
+		     const char *fieldname UNNEEDED,
+		     const char *str TAKES UNNEEDED)
+{ fprintf(stderr, "json_add_string called!\n"); abort(); }
 /* Generated stub for pubkey_from_node_id */
 bool pubkey_from_node_id(struct pubkey *key UNNEEDED, const struct node_id *id UNNEEDED)
 { fprintf(stderr, "pubkey_from_node_id called!\n"); abort(); }

tests/plugins/test_libplugin.c

@@ -9,7 +9,7 @@
 static char *somearg;
 static bool self_disable = false;
 static bool dont_shutdown = false;
-static int dynamic_opt = 7;
+static u32 dynamic_opt = 7;
 
 static struct command_result *get_ds_done(struct command *cmd,
 					  const char *val,
@@ -181,7 +181,7 @@ static struct command_result *json_checkthis(struct command *cmd,
 static char *set_dynamic(struct plugin *plugin,
 			 const char *arg,
 			 bool check_only,
-			 int *dynamic_opt)
+			 u32 *dynamic_opt)
 {
 	int val = atol(arg);
 
@@ -298,23 +298,23 @@ int main(int argc, char *argv[])
 		    plugin_option("somearg",
 				  "string",
 				  "Argument to print at init.",
-				  charp_option, &somearg),
+				  charp_option, charp_jsonfmt, &somearg),
 		    plugin_option_deprecated("somearg-deprecated",
 					     "string",
 					     "Deprecated arg for init.",
 					     CLN_NEXT_VERSION, NULL,
-					     charp_option, &somearg),
+					     charp_option, charp_jsonfmt, &somearg),
 		    plugin_option("selfdisable",
 				  "flag",
 				  "Whether to disable.",
-				  flag_option, &self_disable),
+				  flag_option, flag_jsonfmt, &self_disable),
 		    plugin_option("dont_shutdown",
 				  "flag",
 				  "Whether to timeout when asked to shutdown.",
-				  flag_option, &dont_shutdown),
+				  flag_option, flag_jsonfmt, &dont_shutdown),
 		    plugin_option_dynamic("dynamicopt",
 					  "int",
 					  "Set me!",
-					  set_dynamic, &dynamic_opt),
+					  set_dynamic, u32_jsonfmt, &dynamic_opt),
 		    NULL);
 }

tests/test_plugin.py

@@ -1561,6 +1561,8 @@ def test_libplugin(node_factory):
     l1.daemon.wait_for_log("get_ds_bin_done: NOT FOUND")
 
     # Check dynamic!
+    assert l1.rpc.listconfigs('dynamicopt')['configs']['dynamicopt']['value_int'] == 7
+
     with pytest.raises(RpcError) as err:
         l1.rpc.setconfig('dynamicopt', 4)
     assert err.value.error['message'] == 'I don\'t like \\"even\\" numbers (valid JSON? Try {})!'
@@ -1570,8 +1572,9 @@ def test_libplugin(node_factory):
     assert err.value.error['message'] == 'I don\'t like \\"even\\" numbers (valid JSON? Try {})!'
 
     l1.rpc.check(command_to_check='setconfig', config='dynamicopt', val=9)
-    # FIXME: libplugin doesn't populate defaults!
-    assert 'dynamicopt' not in l1.rpc.listconfigs()['configs']
+
+    # Unchanged!
+    assert l1.rpc.listconfigs('dynamicopt')['configs']['dynamicopt']['value_int'] == 7
 
     l1.rpc.setconfig('dynamicopt', 9)
     conf = l1.rpc.listconfigs('dynamicopt')['configs']['dynamicopt']