test(v6): reproduce custom environment preload injection

[hi-ogawa]

Description

• base feat: v6 - Environment API #16471

@patak-dev I tested alpha.5 in hi-ogawa/vite-environment-examples#51 and it looks like __vitePreload is now injected for custom environment with ssr: true, which wasn't the case in alpha.3.

For now I added a failing test here as you might notice something. I start to read the new builder code, so I might going to find something myself.

It looks like per-environment resolveConfigToBuild is not including environmentOptions from the root config:

vite/packages/vite/src/node/build.ts

Line 1511 in 37190af

environmentConfig = await resolveConfigToBuild(inlineConfig, patchConfig)

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[patak-cat]

Thanks @hi-ogawa! Added a comment here to explain the issue. I'll be reworking our internal plugins to avoid accessing config.build next so we can simplify this patching. This explains why you had issues initially with the way we were handling the environment config during build and you needed to pre-merge the environment options into the config to make things work.

[hi-ogawa]

Thanks for the quick fix! Confirmed alpha.6 is working on my repo hi-ogawa/vite-environment-examples#51