[oyobbeb]

fix #22078

Externalization decisions depend on where a package is imported from, but the current cache only uses the package ID. When the same ID resolves to different packages, the cached decision can incorrectly externalize linked source or inline a CommonJS dependency, depending on import order.

This change adds the directory tryNodeResolve resolves bare imports from to the cache key: the importer's directory if the importer exists on disk, otherwise root. That rule is now a helper (getNodeResolveBasedir) shared by both, so they stay in sync. The externalization resolver also gets its own packageCache.

Unlike #22080's file-level key, importers in the same directory share cached decisions. #22080 is slow mainly because this resolver had no package cache, so every new importer re-reads package.json. With a cache, both keys perform about the same.

Validation

• The three new tests fail on main (a later call gets an earlier call's result) and pass with this change.
• With the reproduction, b a fails on main with ReferenceError: module is not defined, and a b externalizes dep@2. With this change, both orders match loading each package alone.

Benchmark

Vite e954a9c, Node v24.12.0, Apple M5; 2,000 modules across 100 folders, 10 bare imports per module. Median of five cold loads.

Variant	Run 1	Run 2
main	745 ms	671 ms
#22080	1710 ms	1820 ms
Directory key only	734 ms	712 ms
#22080 + shared config.packageCache	731 ms	719 ms
This PR	614 ms	664 ms

Only #22080 without a package cache is clearly slower; the other variants are within run-to-run noise of main.

Reproduction and benchmark: https://github.com/oyobbeb/vite-22078-repro

Review notes

The dedicated packageCache is not cleared when a package.json changes, because the watcher only invalidates config.packageCache. processedIds was never cleared on main either, so this only affects (id, directory) pairs first seen after the change. I kept it separate because config.packageCache stores resolved entries without isProduction in the key, and isProduction is fixed to false here.

AI assistance

AI tools assisted with the investigation, implementation, and tests. I read how tryNodeResolve picks its base directory, reviewed the diff, and chose this approach after comparing the variants above.