Upgrading from enzyme-adapter-react-16@1.15.1 -> 1.15.2 breaks connected component tests

[ryanvanbelkum]

Current behavior

When I upgrade from 1.15.1 of enzyme-adapter-react-16 to version 1.15.2, I am running into JSX comparison test failures with connected components.

Ex.

  const wrapper = shallow(<SomeComponent />).get(0);
  expect(wrapper).toEqualJSX(
    <ConnectedRouter history={history}>
          ...childrenHere
    </ConnectedRouter>
  )

// FAILURE
- <ConnectFunction
+ <Connect(ConnectedRouterWithContext)

Note: toEqualJSX -> https://www.npmjs.com/package/jasmine-expect-jsx is a simple wrapper around react-element-to-jsx-string -> https://github.com/algolia/react-element-to-jsx-string and turns a react element into a JSX string.

Expected behavior

Expect tests to still pass without change after bumping minor version

Your environment

API

• shallow
• mount
• render

Version

library	version
enzyme	3.11.0
react	16.13.1
react-dom	16.13.1
react-test-renderer	16.13.1
adapter (below)	1.15.2

Adapter

• enzyme-adapter-react-16
• enzyme-adapter-react-16.3
• enzyme-adapter-react-16.2
• enzyme-adapter-react-16.1
• enzyme-adapter-react-15
• enzyme-adapter-react-15.4
• enzyme-adapter-react-14
• enzyme-adapter-react-13
• enzyme-adapter-react-helper
• others ( )

[bdwain]

@ljharb i dug into this a bit more and narrowed it down to #2300, specifically this commit, which fixes #2297

I don't totally understand why react change the way they do things, but the change to enzyme's own isMemo seems to be causing this issue. It seems like the component is not typeof(Memo) but does have the $$typeof for a memoized component.

I'll try to get a codesandbox repro up and dig into what is going wrong more.

[ljharb]

@bdwain thanks, appreciate that

[bdwain]

@ljharb here's a code sandbox (open the console) https://codesandbox.io/s/quirky-sun-rpwd3.

Notice that the displayname of the rendered element from the shallow wrapper does not match the display name of the actual element. because it took the inner "type" when calculating it in enzyme.

I'll keep looking at this, but please let me know if something stands out.

[bdwain]

notice in the sandbox that isMemo is false on wrapper.get(0) but true on the plain element. it seems like isMemo returns true on an element normally, but not if it's rendered in the shallow renderer (or maybe mount too). If we can adress that issue, i bet we could go back to using the published isMemo functions.

[bdwain]

i think i found the issue actually @ljharb

enzyme/packages/enzyme-adapter-react-16/src/ReactSixteenAdapter.js

Line 712 in 6d1b57d

return {

There we get the output from the renderer (which i ran through react's isMemo and it returned true) and we just throw it away and lose the type info that react gave it that their new isMemo and isLazy checks are based on.

Is the point of that to give a consistent interface between different react versions? It seems we need some way of maintaining the object's type while creating an object with a consistent interface. does that sound like i'm on the right track?

[bdwain]

Hey @ljharb were you ever able to look at this? It'd be great to get this fixed. I'm happy to help I just want to make sure I'm on the right path before I go too far, and to see if anything jumps out at you given what I found so far.

[ljharb]

Sorry, i haven’t had time to look at it yet.

If you can provide a test case in a PR, with or without a fix, i can get it reviewed and merged and released ASAP :-)

[bdwain]

Thanks @ljharb. I made #2408 and I think that covers it though it was hard to find the right spot for the unit test.

[ljharb]

@bdwain your failing test is helpful, but isMemo(rendererOutput) is returning false for me (update: isMemo(output.type) is passing, however)