Bugfix: crash during startup because of missing 'x-delayed-type'

[spuun]

WHAT is this pull request doing?

If a delayed exchange was declared with type=x-delayed-message and arguments={x-delayed-type: '…'} and LavinMQ crashed before definitions has been compacted, it couldn't start again because of:
Unhandled exception: Missing required argument 'x-delayed-type' (LavinMQ::Error::ExchangeTypeError)

In LavinMQ any exchange can be delayed by specifiy x-delayed-exchange: true in exchange arguments, and declare frames with type=x-delayed-message was converted to type=<value of x-delayed-type> with arguments={x-delayed-exchange: true}. However, the original frame was stored to the definition file, but with modified arguments causing the crash on startup, i.e. the frame had type=x-delayed-message but no x-delayed-type in the arguments table.

This change will make sure to clone the arguments table before modifying it.

HOW can this pull request be tested?

Specs, or run lavinmq and declare a delayed exchange with type=x-delayed-message then kill -9 lavinmq and try start it.

[carlhoerberg]

Can definitions with delayed exchanges be exported and then imported in Rabbit?

[kickster97]

Can definitions with delayed exchanges be exported and then imported in Rabbit?

it will not crash, but they are not compatible.. the exchange will be created on the rabbitmq broker but the x-delayed-exchange: true will be in the arguments rather than the actual type.

To make it fully compatible would probably require a refactor of make_exchange in Vhost