Dom-testing-library: Use debug module for logging instead of console.log

[alexkrolick]

Describe the feature you'd like:

DTL currently provides several debug methods that pretty print the DOM

What if instead of, or in addition to, these methods we added a debug scope using the debug npm module?

https://www.npmjs.com/package/debug

Before:

• write test
• get weird output
• add debug log calls to test

After:

• DEBUG=dom:query:* yarn test (on changed files or with a specific test regex)

Suggested implementation:

Describe alternatives you've considered:

Teachability, Documentation, Adoption, Migration Strategy:

[kentcdodds]

Interesting idea! I wish we'd thought of this before making the debug and log* APIs. We could've said debug will use the debug module and log* uses console.log.

As it is, I don't think this is enough for a breaking change OR for a weird API name. Maybe we can reserve doing this for the next breaking change 🤔

Or maybe it's fine to make a breaking change for this. Thoughts?

[pedroapfilho]

I don't see any issues making a breaking change for the debug API, you only use it once or twice and then remove it from the test itself.

[timdeschryver]

Do we know when the next major release will be released?
I'm fine either way, but if we have some changes lined up I think it would be better to add this one to the list.

[kentcdodds]

Do we know when the next major release will be released?

There's not currently any scheduled major release. And I don't think there are any other needs for a major release.

I have mixed feelings about treating this as an acceptable breaking change. I don't feel like it's necessary enough to warrant doing that. I'm not sure though.

[kentcdodds]

After considering this further, I think we're too far along to make this kind of change. It would be pretty confusing to people I think 😬

[alexkrolick]

🤔 would it be a breaking change to add support for the debug env option while leaving the explicit methods as an option?

[kentcdodds]

After working on an exploratory PR for this, I'm starting to think this is going to be ok. It'll be a bit of an adjustment for folks, but I think they'll figure it out.

[kentcdodds]

So here's my thinking. In DTL we'll have debugDOM and logDOM which basically amount to this:

const debugDOM = (...args) => debug(prettyDOM(...args))
const logDOM = (...args) => console.log(prettyDOM(...args))

Where debug is: const debug = getDebugger('testing-lib')

In RTL, we'll make debug use debugDOM and we'll make a new method called log which calls logDOM. Thoughts?

[alexkrolick]

My initial thought was that this change would enable a verbose log level that doesn't require adding function calls to your tests; every render, query, and event would trigger a debug call automatically under various scopes.

You could still have the manual methods.

DEBUG=testinglib:events jest my-flaky-test
DEBUG=testinglib:queries jest my-flaky-test
DEBUG=testinglib:debug jest my-flaky-test
DEBUG=testinglib:* jest my-flaky-test

[kentcdodds]

Oh, I see what you mean. So you're suggesting that we add debug calls in the DTL source code? Hmmm...

[kentcdodds]

My initial thought is that if people turn that on the resulting output would be way too much to be useful.

[kentcdodds]

I see what you mean. Interesting! I was thinking of something completely different. Yeah, I like this. Wouldn't require a breaking change either.

What I'm going to do is open a PR with some of my refactorings (I'm pretty happy with the resulting code), but I'll leave out my addition of debug and we can do that later.

[alexkrolick]

resulting output would be way too much

Maybe? You'd definitely want to debug one test at a time.

Is there an advantage to changing the debug helper otherwise? Maybe that you could keep the debugger statements in the tests for later rather than deleting them before commit?

Edit: posted at the same time, sounds good 👍

[kentcdodds]

I don't think that I'll personally work on this and it looks like there's not a lot of steam behind it, so I'm going to close this for now. If someone feels strongly about it then we can bring it up again.