  We present ConvLab-2, an open-source toolkit that enables researchers to
build task-oriented dialogue systems with state-of-the-art models, perform an
end-to-end evaluation, and diagnose the weakness of systems. As the successor
of ConvLab (Lee et al., 2019b), ConvLab-2 inherits ConvLab's framework but
integrates more powerful dialogue models and supports more datasets. Besides,
we have developed an analysis tool and an interactive tool to assist
researchers in diagnosing dialogue systems. The analysis tool presents rich
statistics and summarizes common mistakes from simulated dialogues, which
facilitates error analysis and system improvement. The interactive tool
provides a user interface that allows developers to diagnose an assembled
dialogue system by interacting with the system and modifying the output of each
system component.
