tsgo emits files next to source instead of outDir when include references parent directories via ../

[Cellule]

Steps to reproduce

1. Clone the minimal repro: https://github.com/Cellule/tsgo-outdir-repro
2. Run npx --package=@typescript/native-preview@7.0.0-dev.20260130.1 tsgo -p sub/tsconfig.json
3. Observe that common/src/greeter.js is emitted next to the source file instead of in sub/dist/

Project structure

.
├── tsconfig.json            # parent config with outDir: "${configDir}/dist/"
├── common/src/greeter.ts    # shared source file
└── sub/
    ├── tsconfig.json        # extends ../tsconfig.json, includes ../common/src/**/*
    └── src/index.ts         # imports from ../../common/src/greeter.js

tsconfig.json (root):

{
  "compilerOptions": {
    "target": "ES2024",
    "module": "NodeNext",
    "moduleResolution": "NodeNext",
    "outDir": "${configDir}/dist/",
    "strict": true,
    "skipLibCheck": true
  },
  "include": ["common/src/**/*"]
}

sub/tsconfig.json:

{
  "extends": "../tsconfig.json",
  "include": [
    "src/**/*",
    "../common/src/**/*"
  ]
}

Behavior with typescript@5.9

All output files are correctly placed in sub/dist/:

$ npx --package=typescript@5.9 tsc -p sub/tsconfig.json && find . -name '*.js' -not -path '*/node_modules/*'
./sub/dist/sub/src/index.js
./sub/dist/common/src/greeter.js

Behavior with tsgo (@typescript/native-preview@7.0.0-dev.20260130.1)

Files from parent directories (included via ../) are emitted next to the source files instead of in outDir:

$ npx --package=@typescript/native-preview@7.0.0-dev.20260130.1 tsgo -p sub/tsconfig.json && find . -name '*.js' -not -path '*/node_modules/*'
./sub/dist/src/index.js      # file inside sub/ goes to sub/dist/ ✅
./common/src/greeter.js      # file outside sub/ emitted next to source ❌

Note: --showConfig reports the correct resolved outDir:

"outDir": "/path/to/sub/dist"

Bisect result

• Last good version: 7.0.0-dev.20260109.1
• First bad version: 7.0.0-dev.20260111.1

The regression was introduced between these two nightly builds. The 5 commits in that range are:

1. 2a31979f — Preallocate types slice in getLiteralTypeFromProperties (Preallocate types slice in getLiteralTypeFromProperties #2458)
2. 38353bd4 — New auto-import infrastructure (New auto-import infrastructure #2390)
3. 43313db8 — Also clean CI runner for smoke test (Also clean CI runner for smoke test #2464)
4. 0f7cc3dd — Handle long paths in native-preview tsgo entrypoint (Handle long paths in native-preview tsgo entrypoint #2448)
5. 6e1e2c29 — Cache types computed by getLiteralTypeFromProperties (Cache types computed by getLiteralTypeFromProperties #2466)

The most likely culprit is #2390 as the only substantial change touching the compiler.

Additional notes

• The issue is not specific to ${configDir} — using "outDir": "./dist/" produces the same result
• Setting rootDir explicitly does not fix it
• The issue occurs both with and without --build
• The issue also affects the latest nightly (7.0.0-dev.20260206.1)

[jakebailey]

Can you please compare against the 6.0 nightly instead of 5.9?

[jakebailey]

(I was assuming it was rootDir, but it probably isn't)

[Cellule]

Additional finding: comparison with tsc 6.0

tsc 6.0 (nightly 6.0.0-dev.20260207) does not silently emit to the wrong location. Instead it produces a clear error:

$ npx --package=typescript@next tsc -p sub/tsconfig.json
error TS5011: The common source directory of 'tsconfig.json' is '..'. The 'rootDir' setting must be explicitly set to this or another path to adjust your output's file layout.
  Visit https://aka.ms/ts6 for migration information.

So the expected behavior should be one of:

• Emit correctly to outDir (as tsc 5.9 does), or
• Produce TS5011 error asking to set rootDir explicitly (as tsc 6.0 does)

But tsgo currently silently writes .js files next to the .ts sources, which is the worst of both worlds — silent data corruption that can pollute the source tree.

[Cellule]

Confirm that setting the rootDir fixes the issue, so I suppose the real issue here is the lack of error report on tsgo vs tsc v6
Not sure why I initially thought that setting rootDir wouldn't fix it