feat(ssr): tolerate circular imports

[aleclarson]

Description

This PR makes SSR imports work like Node.js in the following way:

Modules that depend on each other will never receive an undefined exports. Instead, the module that is first to import the other module will wait for the other module to be instantiated. When the other module imports the first module, it receives the incomplete exports object, which will be completed when the first module is done being instantiated.

To accomplish this behavior, we need to load SSR dependencies one at a time. This ensures a predictable import order. Before this PR, the import order is non-deterministic, as it depends on the depth of the dependency tree plus the transformation time per module.

This PR also avoids infinite hangs caused by a dependency having its ssrLoadModule promise awaited without first checking if one of its dependencies is within the urlStack.

As of 0333312, this PR also allows the "other module" to access the partial exports of the "first module". For example, if export { foo } from "./foo" comes before export { bar } from "./bar" in the ./index.js module, then ./bar.js will still be able to import { foo } from "./index" and use it before ./index.js has finished being instantiated.

Todo

• Split out the playground/ssr-react changes into a new playground ssr-circular-import

Additional context

Fixes #2258
Fixes #2491

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What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

Before submitting the PR, please make sure you do the following

• Read the Contributing Guidelines.
• Read the Pull Request Guidelines and follow the Commit Convention.
• Check that there isn't already a PR that solves the problem the same way to avoid creating a duplicate.
• Provide a description in this PR that addresses what the PR is solving, or reference the issue that it solves (e.g. fixes #123).
• Ideally, include relevant tests that fail without this PR but pass with it.

[raythurnvoid]

@aleclarson i've brought my improvement to your branch: aleclarson#2

in can still be improved but it works on the project i'm working at the moment

[aleclarson]

@raythurnevoid Thanks for the test case. I've solved it in a better way, see here: 0333312

[raythurnvoid]

@raythurnevoid Thanks for the test case. I've solved it in a better way, see here: 0333312

I can confirm it is working on the project i'm working too

[patak-dev]

@aleclarson would you resolve the conflicts? Is this one ready to be discussed with the team?

[Shinigami92]

Should @brillout have a look?

[brillout]

@Shinigami92 LGTM (Although my review is superficial and I didn't dig that much)

@aleclarson Neat neat - one thing though: how about we create a new playground instead of populating playground/ssr-react/? I often point people to playground/ssr-react and playground/ssr-vue to show them Vite's native SSR API. Would be good for them if we keep these playgrounds minimal. Thoughts?

@LydiaF Hope this makes you re-consider Vite hehe.

[aleclarson]

how about we create a new playground instead of populating playground/ssr-react/? I often point people to playground/ssr-react and playground/ssr-vue to show them Vite's native SSR API. Would be good for them if we keep these playgrounds minimal. Thoughts?

I agree. The tests were contributed by others. If someone can create the new playground, it would be appreciated. 👍

[rtsao]

It seems like there is still possible issues with circular imports and SSR that can lead to intermittent hanging: #11468