Change the behavior of `tsc` on a tsconfig solution

[ArnaudBarre]

🔍 Search Terms

The Vite starters now use a "solution" tsconfig, as documented in the docs.

The issue is that a lot of people are used to run tsc or tsc --noEmit at the root of the project, and now, this silently does nothing.

✅ Viability Checklist

• This wouldn't be a breaking change in existing TypeScript/JavaScript code
• This wouldn't change the runtime behavior of existing JavaScript code
• This could be implemented without emitting different JS based on the types of the expressions
• This isn't a runtime feature (e.g. library functionality, non-ECMAScript syntax with JavaScript output, new syntax sugar for JS, etc.)
• This isn't a request to add a new utility type: https://github.com/microsoft/TypeScript/wiki/No-New-Utility-Types
• This feature would agree with the rest of our Design Goals: https://github.com/Microsoft/TypeScript/wiki/TypeScript-Design-Goals

⭐ Suggestion

I think in that specific case, it should do one of those two things:

• make it an error in that case with "You probably want tsc -b"
• default to build mode (when the tsconfig contains files: [])

📃 Motivating Example

You have three chars less to type? 😅

More seriously, it's about making project references more used without a familiar command becoming useless

💻 Use Cases

2. What shortcomings exist with current approaches?

We get some reports like this: vitejs/vite#17585

I suspect a lot more people fall for this, but find the issue before opening an issue

[RyanCavanaugh]

The issue is that a lot of people are used to run tsc or tsc --noEmit at the root of the project, and now, this silently does nothing

There's supposed to be an error if there are zero input files - do you have a sample we can look at to understand why that's not happening?

[ArnaudBarre]

You can run bun create vite@latest && cd vite-project && bun i && bun tsc (choose React and TypeScript)

[MartinJohns]

There's supposed to be an error if there are zero input files

The related issue is still open: #8344

[RyanMyrvold]

There's supposed to be an error if there are zero input files

The related issue is still open: #8344

Thank you!

[ArnaudBarre]

@RyanMyrvold Your PR looks good expect we should error no matter the noEmit flag, which doesn't impact things given that there is no files anyway.
While the linked issue maybe linked, this predate project references which make the empty case a non important issue.
Here having a dedicated error for this documented pattern make a lot more sense

[RyanMyrvold]

we should error no matter the noEmit flag, which doesn't impact things given that there is no files anyway.

Thanks for pointing that out! I’ll rework the PR to ensure it errors regardless of --noEmit and better aligns with the documented pattern. Let me know if there’s anything else to consider as I revise.

[ArnaudBarre]

Other than that the code diff looks good to me! But I don't know the codebase so I don't if this the right place for the this code 😅

[RyanMyrvold]

A few takeaways from the current configuration

• The error (Referenced project must have set "composite": true) is directly related to the requirements for project references in TypeScript, specifically for projects that emit outputs like .d.ts or .js files.
• For project references to work in a solution, all referenced projects that emit outputs must have "composite": true in their compilerOptions. However, container projects (e.g., solution-style tsconfig files with "files": []) do not appear to require "composite": true. Please feel free to correct me if I’m wrong!

[ArnaudBarre]

What is "the current configuration"?

I don't agree with your second point, for me a solution tsconfig is a special tsconfig that has files: [] and doesn't require linked projects to have composite: true. That's what the default template in Vite does.

[RyanMyrvold]

What is "the current configuration"?

I don't agree with your second point, for me a solution tsconfig is a special tsconfig that has files: [] and doesn't require linked projects to have composite: true. That's what the default template in Vite does.

Thank you for pointing that out

By "the current configuration," I was referring to setups where tsc is run at the root of a project. This relates to the issue because solution-style tsconfig files with "files": [] and no "composite": true can lead to tsc or tsc --noEmit silently doing nothing, which many users might not expect. I think recognizing container projects would help ensure error messages guide users better, especially in cases like running tsc at the root, where it might otherwise fail silently. If I’ve missed something in my understanding, please feel free to correct me—I’d appreciate your insights!

[ArnaudBarre]

Ok I see, we totally agree then!