Add Mojo::Promise handling to the eval command

[jberger]

I find the eval command to be invaluable for one-off usage and testing, especially while developing. As I've been writing more promise apis and now as I'm writing fewer blocking apis due to the existence of Mojo::AsyncAwait, I'm finding the usage of promises in the eval command to be cumbersome to the point of not using it. With this change, one that I doubt would affect any usage in the wild (who wants to dump the stringified promise?), we can make a very comfortable interface for one-off testing of promise apis and make for easy examples and demos for newcomers or answer-seekers on irc.

[jhthorsen]

I’m in favor of this change 👍

[kraih]

I never had a need for this, so not sure how to vote.

[jberger]

I never had a need for this, so not sure how to vote.

I had only rarely until a new project at $work. Since async functions necessarily return promises and since they nearly obviate the need for blocking apis I now have an app for which the model is entirely promises. I think once aa becomes more common this will be the case more and more often, it feels very natural

[jberger]

@marcusramberg I know you're on vacation, but if you get a second, I'd appreciate a review/vote

[jberger]

Per the new PR policy, I'm calling a vote on this PR. @mojolicious/core

[kraih]

Neutral vote from me.

[marcusramberg]

I'm also in favor of this change 👍

[s1037989]

What do you think about adding a Usage example?

Usage: APPLICATION eval [OPTIONS] CODE

  ./myapp.pl eval 'say app->ua->get("/")->result->body'
  ./myapp.pl eval 'say for sort keys %{app->renderer->helpers}'
  ./myapp.pl eval -v 'app->home'
  ./myapp.pl eval -V 'app->renderer->paths'
  ./myapp.pl eval -V '

I don't know if this is a good example, but something like:

  ./myapp.pl eval -v 'app->ua->get_p("https://mojolicious.org")->then(sub{shift->result->dom->at("title")->text})'