jest-haste-map 22.4.0 breaks in node-chakracore

[jdalton]

Just a heads up. I have a unit test that checks jest + mock-require and it started failing after with the `jest-haste-map 22.4.0 update (on Windows 10).

\cc @SimenB

[jdalton]

It is probably related to this bit jestjs/jest@3a2854a#diff-9450b62547fd20fe4b1669dd088f14af.

The error I get is

TypeError: Unable to get property 'files' of undefined or null reference
   at Anonymous function (C:\projects\esm\node_modules\jest-haste-map\build\index.js:324:7)

It's reading a haste cache file but the file is empty, "".

[SimenB]

Can you try with 22.4.2? Ref jestjs/jest#5642.

Doesn't chakra node support v8.serialize? Which would be understandable, but then we shouldn't hit that code path anyways.

Underlying change: jestjs/jest#5565

[jdalton]

I actually worked backwards from 22.4.2. The first version to work again was 22.3.0.

[SimenB]

/cc @mjesun

[MSLaguana]

The v8.deserialize method seems to have nothing to do with v8, and it's implemented in node so we should support it. It looks to me like right now the native methods it calls into are being mis-compiled into do-nothing functions, so it is returning undefined.

[MSLaguana]

Ah nevermind; the node_serdes serialization methods end up depending on a v8 type that we don't mock out, and so the compiler was calling our bluff.

[mjesun]

Sorry for the late reply, I just got an email about that (thanks, GitHub...). From what you say it looks like it's not a particular bug in Jest?

What would work as well for you is if you don't provide v8.serialize at all. In that case, we default back to an implementation with a standard JSON.stringify.

[MSLaguana]

The difficulty with that is we kind-of/kind-of-don't support everything in the v8.js file. The simplest thing from our side would be to remove v8.js, but then your require("v8") would throw and that looks like it'd be worse for you at the moment. The alternative that you propose is essentially having v8.js as an empty file, which isn't too unreasonable, but as a general rule we try to keep our diff from upstream node as small as possible.

[digitalinfinity]

I think it's not unreasonable for v8.js to just return an empty object if process.jsEngine != 'v8'. @addaleax thoughts? (and yes, we probably should get around to supporting serdes at some point, it's still on my backlog 😞)

[mjesun]

@MSLaguana I can wrap the V8 require in a try/catch prior to check v8.serialize; would that make things simpler?

[MSLaguana]

I've just put out a PR to have the v8 module be an empty object: #491

[MSLaguana]

This should be fixed in nightlies now, triggering the fallback to JSON.parse

[kfarnung]

The fix was also backported to our latest release build: https://github.com/nodejs/node-chakracore/releases/tag/node-chakracore-v8.10.0