db_exec_mayfail: variant of db_exec where we actually expect an error.

There's one caller where db_exec can actually fail due to constraints,
and we rely on it.

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

wallet/db.c

@@ -197,6 +197,23 @@ bool PRINTF_FMT(3, 4)
 	return true;
 }
 
+bool db_exec_prepared_mayfail_(const char *caller, struct db *db, sqlite3_stmt *stmt)
+{
+	if (db->in_transaction && db->err) {
+		goto fail;
+	}
+
+	if (sqlite3_step(stmt) != SQLITE_DONE) {
+		goto fail;
+	}
+
+	sqlite3_finalize(stmt);
+	return true;
+fail:
+	sqlite3_finalize(stmt);
+	return false;
+}
+
 sqlite3_stmt *PRINTF_FMT(3, 4)
     db_query(const char *caller, struct db *db, const char *fmt, ...)
 {

wallet/db.h

@@ -112,6 +112,15 @@ sqlite3_stmt *db_prepare_(const char *caller, struct db *db, const char *query);
 #define db_exec_prepared(db,stmt) db_exec_prepared_(__func__,db,stmt)
 bool db_exec_prepared_(const char *caller, struct db *db, sqlite3_stmt *stmt);
 
+/**
+ * db_exec_prepared_mayfail - db_exec_prepared, but don't set db->err if it fails.
+ */
+#define db_exec_prepared_mayfail(db,stmt) \
+	db_exec_prepared_mayfail_(__func__,db,stmt)
+bool db_exec_prepared_mayfail_(const char *caller,
+			       struct db *db,
+			       sqlite3_stmt *stmt);
+
 bool sqlite3_bind_short_channel_id(sqlite3_stmt *stmt, int col,
 				   const struct short_channel_id *id);
 bool sqlite3_column_short_channel_id(sqlite3_stmt *stmt, int col,