Emit events before and after executing a message

[alcuadrado]

This is a WIP PR, as I'm not sure about

1. Where to document this
2. Where to test it. Should I create a new file in tests/api?

Closes #574

[s1na]

Where to document this

I just noticed we lack a comprehensive doc for the events. The API docs don't currently include the events. Should we maybe collect a list of the events in the README? Not sure where would be a good place for that.

Where to test it. Should I create a new file in tests/api?

Hm, the easiest would probably be in the GeneralStateTests as they already run txes with multiple messages and already do listen to some events, e.g.:

https://github.com/ethereumjs/ethereumjs-vm/blob/c3d7a57971a54b91294f37cd5f9b329733d89740/tests/GeneralStateTestsRunner.js#L78

but on the other hand, those tests are rather a black-box and we don't know the expected result for each message in advance

[holgerd77]

Yes, events should really be documented (think we had some basic version before we switched to auto-generated docs, not sure?). Some are some techniques to do this with documentation, but maybe for now some manual addition to README will also do as @s1na suggested?

For tests I would find this more fitting as a new file in tests/api.

Update: did a quick search and found e.g. this on former event documentation, maybe we should simply do an adopted re-integration of the text in the README?

[holgerd77]

Hi @alcuadrado, will you be able to add some docs and tests on this soon, so that we eventually can include in a subsequent v4.1.0 release (not too far away I think so that we incrementally get the Istanbul features out of the door and people can test)? Or shouldn't we wait for this and release independently?

[alcuadrado]

I added tests for all of the events in this PR, and added documentation about them in the README.

[coveralls]

Coverage increased (+0.1%) to 95.818% when pulling beb0892 on message-events into 7d9cc76 on master.

[alcuadrado]

Oops, this was outdated wrt master. I rebased it.

[holgerd77]

Looks good, thanks! 😄

[holgerd77]

@s1na @alcuadrado I would now prepare release notes for a v4.1 release on Thursday.

[alcuadrado]

Sounds good! Thanks