Incompatibility of version 6.13.1 with older version (silent failure to track changes)

[spion]

Intended outcome:

This is not exactly a bug, but I thought I'd mention it because it can easily be relevant in larger projects and monorepos. Its quite possible for multiple versions of mobx to be installed in a monorepo, and while this is suboptimal (in terms of bundle size and similar), its not typically a true bug.

However, I would expect 6.13.1 to warn when running alongside older versions and report an error, because the changes in internals are significant enough that observables coming from older versions are completely broken / inert when used in a 6.13.1 context.

Actual outcome:

No errors are reported, however changes in observables from an older version of mobx are simply not tracked successfully by 6.13.1

How to reproduce the issue:

Unfortunately, its a bit difficult to create a reproduction case. A monorepo with multiple versions of mobx would be needed

Versions

6.13.1

Workaround

Update the entire monorepo and any relevant dependencies that depend on mobx to 6.13.1

Expectations

It would be good if this situation could be detected and would result with a warning in the console or similar.

[mweststrate]

In principle we should have protection against this, and we can bump the version number here if needed:

https://github.com/mobxjs/mobx/blob/main/packages/mobx/src/core/globalstate.ts#L32-L186

So I think we can just bump the version number there and we should be OK.

[johnnywang]

Came across this issue from a comment on this PR, after trying to debug why our mobile app stopped reacting to changes, where all UI interaction renders seemed to happen a render cycle late.

Narrowed it down to an upgrade we did to the latest mobx, and after trying a bunch of versions out, noticed this same thing, where things are working fine up to 6.13.0, but break as of 6.13.1. Not really sure how or why this is broken, and like the OP mentions here, I'm not seeing any warnings or errors anywhere.

And while we DO have a monorepo, the mobile app is built as a standalone project, and doesn't have duplicate versions of mobx inside the yarn.lock