[utils] Fix isPlainObject to work across realm

[brijeshb42]

This update adds support for checking plain object in other runtimes as well (ie vercel edge-runtime)

The implementation has been borrowed from https://github.com/sindresorhus/is-plain-obj to support our bare-minimum use-case.

Other simpler way would be to also add check for edge runtime but it will only cover Vercel's runtime and will be a short-term fix.

Closes #23739
Closes #39338
Closes #38177

[mui-bot]

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[siriwatknp]

@brijeshb42 I need more context. Is this the only function that does not work with edge runtime? How do I test locally that the change is not working?

[brijeshb42]

@siriwatknp You can use a local next.js project with edge runtime in dev mode. I followed the instructions mentioned #39338. This is the repo.
In edge runtime, obj.constructor is not equal to Object. That was the main reason createTheme was just returning the theme created from @mui/system's createTheme.
createTheme (from @mui/material) internally uses deepmerge which in turn has the check isPlainObject which will always return false in case of edge runtime. This will not merge the two objects passed to deepmerge which will then just return the first object passed to it.

This was resulting in critical tokens being undefined and throwing errors.

[oliviertassinari]

Does it relate to #23739 (comment)?

[brijeshb42]

Yes. Seems root cause is same for both the issues.

Edit: The core issue is similar but in this particular, it's not about checking objects across realms. Instead, here, the realm itself is different.

[oliviertassinari]

Ok, then I think to bring the regression test in, and to consider if the implementation can't be simplified to improve performance. I suspect lodash tests for cases we don't need to support.

[juniorbotelho]

When will this pull request be merged into the master branch?

[oliviertassinari]

I rebased on HEAD.

[oliviertassinari]

This change is missing the point of the test. Reverted in fd12e42.

[oliviertassinari]

I pushed a new commit to remove vm-browserify. It feels like we don't need to run the test in a new iframe, that the node vm module is enough, keeping the stack simpler.