TSC version 5.5.3 - output file looses triple slash reference comment hence compilation fails

[dbaeumer]

🔎 Search Terms

tripple slash reference path

🕗 Version & Regression Information

• This changed between versions 5.4.5 and 5.5.3

⏯ Playground Link

No response

💻 Code

Steps to reproduce:

• clone https://github.com/dbaeumer/tsc-bug.git
• cd into tsc-bug
• npm install
• cd p1
• npm run compile

See everything compiles correctly and the p1/lib/common/api.d.ts file has a /// reference comment at the top

• run git clean -xfd .
• open package.json file in the workspace root and change the typescript dependency from ^5.4.5 to ^5.5.3
• npm install
• cd p1
• npm run compile

🙁 Actual behavior

The compile fails complaining about the missing Thenable in lib/common/api.d.ts

lib/common/api.d.ts:1:32 - error TS2304: Cannot find name 'Thenable'.

1 export declare function foo(): Thenable<string>;

Also observe that the p1/lib/common/api.d.ts file has NO /// reference comment at the top

🙂 Expected behavior

Code compiles like it did under 5.4.5

Additional information about the issue

No response

[MartinJohns]

This is working as intended and documented: https://devblogs.microsoft.com/typescript/announcing-typescript-5-5/#simplified-reference-directive-declaration-emit

[jakebailey]

Yes, this is working as designed. Add preserve="true" to directives you intend to be included in the compiled output.

[jakebailey]

Based on the example and the project where it came from (https://github.com/microsoft/vscode-languageserver-node/blob/6d2a392547ea60db1723e027b4b55d268aa282ea/server/typings/thenable.d.ts), this could just be a type defined and imported, which would end up being handled properly. (Not sure why it's a global...)

[dbaeumer]

@jakebailey good question. It has always been that way I and don't really know why we went down that path 10 years ago ;-). I will look what the best way to fix it is.