fix: compute getPkgName only when used

[vwkd]

Description

Fixes #4698.

This computes getPkgName only when used within the OR operation, allowing for no package name if a libOptions.fileName is provided due to short circuiting. The check for libOptions isn't included anymore, because it's already present as the condition for when resolveLibFilename is called.

I'm unsure how to include tests as I'm unfamiliar with such a big project.

EDIT: Oh, I saw #4726 too late! Feel free to close this then.

EDIT 2: Thanks to @OneNail for the inspiration of the error message.

EDIT 3: I added tests for the cases covered by this change.

Additional context

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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.

[Shinigami92]

The other solution throws an error https://github.com/vitejs/vite/pull/4726/files#diff-aa53520bfd53e6c24220c44494457cc66370fd2bee513c15f9be7eb537a363e7R644

I personally like your solution therefore more, cause it does not throw an error, but do stuff silently 🚀/🤔

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Edit: Damn 🙁 Tests failing 😢 @vwkd

[Shinigami92]

Now it also throws an error 😢 So it is kinda the same as the other PR, and I don't prefer this PR instead of the other PR 🤷
So I'm for the solution that is just working (the other PR tests are green 👀 )

[vwkd]

@Shinigami92 Thanks, I think I know why the CI failed. It's because packages/vite/src/node/__tests__/build.spec.ts still uses the old resolveLibFilename where the arguments changed.

I updated the tests and I hope the CI now passes. It's difficult for me to test locally, because I see many unrelated failures that I don't see on the CI.

EDIT: Also added two new tests for this bug.

[Shinigami92]

[...] many unrelated failures that I don't see on the CI

I know you pain 😢

[Shinigami92]

🎉