The Dart programming language includes built in support for asynchrony colloquially known as async-await. Recently, the implementation has been extended to support debugging, allowing users to step in and out of asynchronous methods.

Much as the async-await constructs allow code to be expressed in a manner closer to the traditional synchronous model, the debugging support allows programmers to debug their asynchronous code almost as if it were being invoked synchronously. We describe the virtual machine’s support for asynchrony and debugging.