lightningd: add json_add_amount_msat and json_add_amount_sat helpers.

These create two fields, one old one which is purely numeric,
and a modern on with a suffix, eg "msatoshi" and "amount_msat".

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

lightningd/json.c

@@ -328,3 +328,25 @@ void json_add_escaped_string(struct json_stream *result, const char *fieldname,
 	if (taken(esc))
 		tal_free(esc);
 }
+
+void json_add_amount_msat(struct json_stream *result,
+			  struct amount_msat msat,
+			  const char *rawfieldname,
+			  const char *msatfieldname)
+{
+	json_add_u64(result, rawfieldname, msat.millisatoshis);
+	json_add_member(result, msatfieldname, "\"%s\"",
+			type_to_string(tmpctx, struct amount_msat, &msat));
+}
+
+void json_add_amount_sat(struct json_stream *result,
+			 struct amount_sat sat,
+			 const char *rawfieldname,
+			 const char *msatfieldname)
+{
+	struct amount_msat msat;
+	json_add_u64(result, rawfieldname, sat.satoshis);
+	if (amount_sat_to_msat(&msat, sat))
+		json_add_member(result, msatfieldname, "\"%s\"",
+				type_to_string(tmpctx, struct amount_msat, &msat));
+}

lightningd/json.h

@@ -7,6 +7,7 @@
 #include "config.h"
 #include <ccan/short_types/short_types.h>
 #include <ccan/tal/tal.h>
+#include <common/amount.h>
 #include <stdbool.h>
 #include <stddef.h>
 #include <stdint.h>
@@ -127,6 +128,20 @@ void json_add_hex_talarr(struct json_stream *result,
 			 const char *fieldname,
 			 const tal_t *data);
 
+/* Adds both a 'raw' number field and an 'amount_msat' field */
+void json_add_amount_msat(struct json_stream *result,
+			  struct amount_msat msat,
+			  const char *rawfieldname,
+			  const char *msatfieldname)
+	NO_NULL_ARGS;
+
+/* Adds both a 'raw' number field and an 'amount_msat' field */
+void json_add_amount_sat(struct json_stream *result,
+			 struct amount_sat sat,
+			 const char *rawfieldname,
+			 const char *msatfieldname)
+	NO_NULL_ARGS;
+
 enum address_parse_result {
 	/* Not recognized as an onchain address */
 	ADDRESS_PARSE_UNRECOGNIZED,

lightningd/test/run-jsonrpc.c

@@ -3,6 +3,10 @@
 #include "../json.c"
 
 /* AUTOGENERATED MOCKS START */
+/* Generated stub for amount_sat_to_msat */
+ bool amount_sat_to_msat(struct amount_msat *msat UNNEEDED,
+					   struct amount_sat sat UNNEEDED)
+{ fprintf(stderr, "amount_sat_to_msat called!\n"); abort(); }
 /* Generated stub for db_begin_transaction_ */
 void db_begin_transaction_(struct db *db UNNEEDED, const char *location UNNEEDED)
 { fprintf(stderr, "db_begin_transaction_ called!\n"); abort(); }