common: move now-enlarged command_fail_badparam into its own source file.

It's getting a bit awkward to inline now: it's non-trivial.

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

common/json_command.c

@@ -0,0 +1,33 @@
+#include "config.h"
+#include <common/json_command.h>
+
+struct command_result *
+command_fail_badparam(struct command *cmd,
+		      const char *paramname,
+		      const char *buffer,
+		      const jsmntok_t *tok,
+		      const char *msg)
+{
+	if (command_dev_apis(cmd)) {
+		return command_fail(cmd, JSONRPC2_INVALID_PARAMS,
+				    "%s: %s: invalid token '%.*s'",
+				    paramname, msg,
+				    json_tok_full_len(tok),
+				    json_tok_full(buffer, tok));
+	}
+
+	/* Someone misconfigured LNBITS with "" around the rune, and so the
+	 * user got a message about a bad rune parameter which *contained the
+	 * rune itself*!.  LNBITS should probably swallow any JSONRPC2_* error
+	 * itself, but it is quite possibly not the only case where this case
+	 * where this can happen.  So we are a little circumspect in this
+	 * case. */
+	command_log(cmd, LOG_INFORM,
+		    "Invalid parameter %s (%s): token '%.*s'",
+		    paramname, msg,
+		    json_tok_full_len(tok),
+		    json_tok_full(buffer, tok));
+	return command_fail(cmd, JSONRPC2_INVALID_PARAMS,
+			    "%s: %s: invalid token (see logs for details)",
+			    paramname, msg);
+}