`rootDirs` / `outDir` options behaviour change depending on files

[homersimpsons]

🔎 Search Terms

"rootDirs", "outDir"

🕗 Version & Regression Information

• This fails with typescript@5.8.3

⏯ Playground Link

No response

💻 Code

// src/index.ts
function foo() { return 'bar'; }
// test/index.ts
function foo() { return 'bar'; }
// tsconfig.json
{"compilerOptions": {"outDir": "./dist", "rootDirs": ["./src", "./test"]}}

🙁 Actual behavior

Running tsc with both src/index.ts and test/index.ts outputs 2 files: dist/src/index.js and dist/test/index.js.

BUT running the same command without test/index.ts outputs 1 file: dist/index.js, here the src directory is missing.

🙂 Expected behavior

running the same command without test/index.ts should output 1 file: dist/src/index.js, (with the srcdirectory).

Additional information about the issue

No response

[MartinJohns]

Are you certain rootDirs actually has any effect on this?

This sounds like it's working as intended, following the documentation of rootDir:

Default: The longest common path of all non-declaration input files.

[homersimpsons]

Are you certain rootDirs actually has any effect on this?

This sounds like it's working as intended, following the documentation of rootDir:

Default: The longest common path of all non-declaration input files.

Ah in fact you are right I had to set "rootDir": "." to have the correct behaviour, sorry for the noise.

[RyanCavanaugh]

This is indeed confusing and we intend to change it at 6.0 #54500