`effect-tsgo patch` mutates Bun’s global virtual store

[tifandotme]

Summary

effect-tsgo patch --typescript modifies the installed TypeScript-Go binary in place. With Bun's global virtual store enabled, that binary is inside a shared cache, so patching one project changes the compiler used by other projects with the same dependency resolution.

The same applies to the Oxlint integration selected by effect-tsgo patch --oxlint.

Environment

• Bun 1.4.2
• @effect/tsgo 0.45.0
• TypeScript 7.0.2
• macOS arm64
• linker = "isolated"
• globalStore = true

Reproduction

Create two projects with the same dependencies and point both at one Bun store:

tmp=$(mktemp -d)
trap 'rm -rf "$tmp"' EXIT

for project in a b; do
  mkdir -p "$tmp/$project"
  cat > "$tmp/$project/package.json" <<'JSON'
{"name":"tsgo-global-store-repro","private":true,"dependencies":{"@effect/tsgo":"0.45.0","typescript":"7.0.2"}}
JSON
  cat > "$tmp/$project/bunfig.toml" <<'TOML'
[install]
linker = "isolated"
globalStore = true
hoist = false
TOML
  (cd "$tmp/$project" && BUN_INSTALL="$tmp/bun" BUN_INSTALL_GLOBAL_STORE=1 bun install --ignore-scripts)
done

(cd "$tmp/a" && \
  BUN_INSTALL="$tmp/bun" BUN_INSTALL_GLOBAL_STORE=1 \
  node_modules/.bin/effect-tsgo patch --typescript)

realpath "$tmp/a/node_modules/.bun/@typescript+typescript-darwin-arm64@7.0.2/node_modules/@typescript/typescript-darwin-arm64/lib/tsc"
realpath "$tmp/b/node_modules/.bun/@typescript+typescript-darwin-arm64@7.0.2/node_modules/@typescript/typescript-darwin-arm64/lib/tsc"

Both paths resolve to the same file under BUN_INSTALL/install/cache/links/. The patch command creates the .original backup and replaces that shared file. Project b observes the patched binary even though it was never patched.

Expected behavior

Patching one project should not modify a package shared by other projects. The command could create a project-local copy or overlay, or refuse to patch a target outside the project with an actionable error.

BUN_INSTALL_GLOBAL_STORE=0 avoids the problem because the target package is materialized inside the project. That workaround removes the main storage benefit of Bun's global virtual store.

The current patcher performs the in-place rename and copy in _packages/tsgo/src/patcher/index.ts.

[mattiamanzati]

Unfortunately this is a known issue for now.
We have an upcoming alternative way to the patching that will use overridden dependencies and alternative packages, but that has its trade offs too.