Extract deepEqual implementation with tests to share it with other libraries?

[jzaefferer]

At least node has its own implementation of deepEqual, as part of the assert module. I have no idea how close their implementation is to ours, might be worth investigating.

[jzaefferer]

Looking around a bit, I found three distinct implementations, all with their own tests. There's definitely potential to share at least tests, better yet implementation.

• substack's node-deep-equal implementation, tests
• chai's deep-eql implementation, tests
• node's deepEqual implementation, tests (roughly)

Not sure how to go about this, and don't yet know the history behind any of these.

[jzaefferer]

For anyone interested in this: Should try to port QUnit's tests to one or all of the other modules and see what fails. We can use those failures to start a discussion with the module owner, along with talking about browser support and whatever else.

[jzaefferer]

After talking to @jdalton about this: We should try to replace our deepEqual implementation with the one in lodash. We can run our existing tests to see if there are (significant) differences in the design. If it works out well, we could promote the lodash implementation to those other projects listed above.

[jzaefferer]

@jdalton I've read https://lodash.com/custom-builds and some other resources, but don't see an option for a (custom) compat build with just isEqual (with dependencies, global or umd exports). What am I missing?

[jdalton]

via lodash-cli:

lodash include=isEqual

of via browserify after you npm i lodash.isequal:

browserify -r lodash.isequal -s isEqual -o lodash.isequal.js

[jzaefferer]

I just tried to replace the QUnit.equiv call in assert.js to use _.isEqual instead, and all tests still pass. That's great!

Still need to figure out how to properly integrate lodash into our build, since this is the first external dependency.

[jdalton]

Still need to figure out how to properly integrate lodash into our build, since this is the first external dependency.

You could go the webpack route and include isEqual as either require('lodash/lang/isEqual') or require('lodash.isequal').

I can prep a PR tonight to flesh a possible approach out.

[leobalter]

That would be great, @jdalton!

It looks like replacing internal deepEqual is the easiest part, but it needs some good strategy using webpack/browserify.

[jzaefferer]

Yeah, switching to internal modules internally is currently the bigger issue. Though if we make that work with webpack, it'll be super easy to add external modules.

[jzaefferer]

@jdalton any idea if you'll be able to work on this?

[jdalton]

Yes, I'll try to get something working this weekend. Last weekend I was unblocking rollup (es6 module bundler). This weekend can be QUnit bundling time. The switch may want to be put on hold though until after the 4.0 bump as lodash's 3.10.1 doesn't support map/set comparisons.

[jzaefferer]

Sounds goood. Making progress on bundling will be valuable either way.

[jdalton]

I should revisit this now that v4 is out.

[jzaefferer]

That would be great! I think our deepEqual implementation has seen some improvements, but that shouldn't stop us from replacing it.

[leobalter]

I think our deepEqual implementation has seen some improvements, but that shouldn't stop us from replacing it.

yes, I'm looking forward to it.

[Krinkle]

Closing for now as I don't expect us to do this any time soon. However if there are one or more persons interested in working on this and have a use case lined up for another library that would consume it, I'd be happy to see this re-open.