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

Beginne damit, den Back-Reference-Import im verlinkten Repository ts-repro-back-reference-import zu reproduzieren, und untersuche die beteiligten Projektverweise in tsconfig.json. Vergleiche die vorhandene TS6307-Diagnose mit dem vorgeschlagenen zusätzlichen Kontext und ermittle anschließend die Stellen in der TypeScript-Compiler-Diagnose und den Tests, die die Einbindung von Projektdateien behandeln. Als erledigt gilt die Aufgabe, wenn der inkorrekte Import eine spezifische, umsetzbare Meldung erzeugt, ohne das Verhalten gültiger Projektverweise zu ändern.