Add a specific error message for disallowed imports in project references?

Suggestion

🔍 Search Terms

project reference back import

✅ Viability Checklist

My suggestion meets these guidelines:

• 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 feature would agree with the rest of TypeScript's Design Goals.

⭐ Suggestion

After introducing project references to a monolith repo with many developers, I've sometimes seen confusion over people writing imports from projects in the incorrect direction: e.g. if project B has a tsconfig reference to project A, trying to import from B in A. ♻️

https://github.com/JoshuaKGoldberg/ts-repro-back-reference-import

Here's an example error message that says what's technically wrong but doesn't give much context:

src/a/index.ts:1:19 - error TS6307: File '---/src/b/index.ts' is not listed within the file list of project '---/src/a/tsconfig.json'. Projects must list all files or use an 'include' pattern.

1 import { b } from "../b";
                    ~~~~~~

📃 Motivating Example

Adding a specific error for these incorrect direction ("back") imports might help folks new to project references understand what they're doing wrong:

src/a/index.ts:1:19 - error TS6307: File '---/src/b/index.ts' is not listed within the file list of project '---/src/a/tsconfig.json'. Projects must list all files or use an 'include' pattern.

  File "---/b/index.ts" is included in "---/b/tsconfig.json", but "---/a/tsconfig.json" does not list a reference to "---/b/tsconfig.json".

1 import { b } from "../b";
                    ~~~~~~

💻 Use Cases

https://github.com/JoshuaKGoldberg/ts-repro-back-reference-import

Inizia riproducendo l'importazione di back-reference nel repository collegato ts-repro-back-reference-import e ispeziona i riferimenti al progetto di tsconfig.json coinvolti. Confronta la diagnostica TS6307 esistente con il contesto aggiuntivo proposto, quindi individua le posizioni nella diagnostica del compilatore TypeScript e nei test che gestiscono l'inclusione dei file di progetto. Il lavoro è completato quando l'importazione errata produce un messaggio specifico e azionabile senza modificare il comportamento valido dei riferimenti al progetto.