Gatsby: Recent MDX PR changed function signature of `createMDXNode`

[laurieontech]

See #25911

A recent perf improvement changed the return object in createMDXNode (https://github.com/gatsbyjs/gatsby/pull/25757/files#diff-15e9617772dbbdaa3f4c5399f3291de9R42)

It also changed the arguments passed to it.

This is a breaking change for those who were calling the function directly in the their gatsby-node.js file.

We should figure out if this is a necessary breaking change and document/bump versions accordingly. Or figure out a different option that won't be.

[johno]

Hmm, yeah this usage is technically an "undocumented" API, but also exists on developer blogs. So we should probably make sure we're being backwards compatible here if we can be.

[elrumordelaluz]

but also exists on developer blogs.

Thanks @johno for the link, I was using this technique but didn't remember where I pick it.

Looking forward to the progress of this PR. Also available to provide any info regarding _use cases_.

[johno]

We've gone ahead and reverted the breaking PR (thanks to @laurieontech) and we'll explore a new way to integrate these performance improvements next week so they don't break this use case.

We'll keep you updated!

[pvdz]

Ok. The API was not public but used anyways.

Guess we'll keep it as is and deprecate it. I'll create a new function to do what needs to be done, issue a deprecation warning for the existing function and warn about perf implications of when the user keeps using it, or using something that uses it.

[pvdz]

(Going to close this issue as the commit was reverted and will take a safer appraoch when trying again)