Avoid deprecation warnings in node.js 10 because we have methods called inspect

[papandreou]

nodejs/node#15549 🙄

In node.js 10+ the custom inspection function for our promises works, but causes a deprecation warning to be logged:

Ditto for Unexpected#inspect:

The fix is to provide the custom inspection function via a symbol exported as require('util').inspect.custom instead. But because we're also using the inspect method name for other things in Unexpected, we're forced to provide the symbol method on all objects that have an inspect method. This PR fixes that up so we provide both in node versions where the custom symbol exists.

[alexjeffburke]

Nice that we get rid of a deprecation warning but what we've had to do just seems.. 😬

Just to understand, we're not allowed to have an .inspect() method without registering it with the node runtime?

[papandreou]

Just to understand, we're not allowed to have an .inspect() method without registering it with the node runtime?

Yeah, pretty much. If we have a method anywhere called inspect, node.js 10+ will print that deprecation warning unless the same object also has a method with a name of require('util').inspect.custom.

It seems our only alternative is to rename our own inspect to something else. That would be breaking and it would be really annoying to have to do that because of a poor deprecation strategy in node.js. I have no idea why they chose to do it like this, it's really disruptive.

[alexjeffburke]

Better that we don't show the deprecation warning of course, but I wish we didn't have to do this. As discussed with @papandreou, it's good this is being cleaned up in node land but outputting a deprecation warning affects all places where it meant something else.

[sunesimonsen]

Would it be an option to not call inspect on objects? I this this behavior was introduced from the very first prototype of inspection in Unexpected. Maybe things have improved 😊

[sunesimonsen]

Sorry about closing the PR. That happens too often on the phone.

[papandreou]

Would it be an option to not call inspect on objects?

Sorry, I don't understand the suggestion? It's the node repl (and require('util').inspect) that calls inspect on objects, not us.

[papandreou]

@sunesimonsen, I'll interpret your silence as an approval ;)