lightningd: check command should return as much detail as possible.

If they're explicitly calling "check", don't obfuscate the result!

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

common/json_command.c

@@ -8,7 +8,7 @@ command_fail_badparam(struct command *cmd,
 		      const jsmntok_t *tok,
 		      const char *msg)
 {
-	if (command_dev_apis(cmd)) {
+	if (command_dev_apis(cmd) || command_check_only(cmd)) {
 		return command_fail(cmd, JSONRPC2_INVALID_PARAMS,
 				    "%s: %s: invalid token '%.*s'",
 				    paramname, msg,

tests/test_misc.py

@@ -4244,3 +4244,9 @@ def test_badparam_discretion(node_factory):
         l1.rpc.checkrune(rune='THIS IS NOT ACTUALLY A RUNE')
 
     l1.daemon.wait_for_log(r"checkrune: Invalid parameter rune \(should be base64 string\): token '\"THIS IS NOT ACTUALLY A RUNE\"'")
+
+    # But: check command *SHOULD* give as much info as we can.
+    with pytest.raises(RpcError, match='rune: should be base64 string: invalid token') as err:
+        l1.rpc.check('checkrune', rune='THIS IS NOT ACTUALLY A RUNE')
+
+    assert err.value.error['message'] == "rune: should be base64 string: invalid token '\"THIS IS NOT ACTUALLY A RUNE\"'"