TS 5.5 - Imports used by decorator output are removed

[RomainLanz]

🔎 Search Terms

remove import compilation decorator

🕗 Version & Regression Information

• This changed between versions 5.4 and 5.5

⏯ Playground Link

https://github.com/RomainLanz/typescript-output-issue

npm install
npm run build

💻 Code

import { DateTime } from "luxon";
import { column } from "@adonisjs/lucid/orm";

class User {
  @column.dateTime()
  declare createdAt: DateTime;
}

🙁 Actual behavior

When compiled the DateTime import is being removed (because it is only used as a type in our file), but the compilation of @column.dateTime() will use the import.

// ...

import { column } from "@adonisjs/lucid/orm";
class User {
}
__decorate([
    column.dateTime(),
    __metadata("design:type", typeof (_a = typeof DateTime !== "undefined" && DateTime) === "function" ? _a : Object)
], User.prototype, "createdAt", void 0);

🙂 Expected behavior

The import should be kept like in TypeScript 5.4.

import { DateTime } from "luxon";
import { column } from "@adonisjs/lucid/orm";
class User {
}
__decorate([
    column.dateTime(),
    __metadata("design:type", typeof (_a = typeof DateTime !== "undefined" && DateTime) === "function" ? _a : Object)
], User.prototype, "createdAt", void 0);

Additional information about the issue

No response

[RomainLanz]

Here is a discussion that may be related : https://github.com/microsoft/TypeScript/issues/54493#issuecomment-1615409830

[Max10240]

met this too

[zanminkian]

That means a project which enables following features at the same time will be unusable under TS 5.5:

1. enable both emitDecoratorMetadata and experimentalDecorators in tsconfig.
2. use declare keyword for class properties.
3. verbatimModuleSyntax is false.

Some of my projects cannot upgrade to TS 5.5 too.

[jakebailey]

Using https://www.npmjs.com/package/every-ts, this bisects to #58366. @weswigham

[jakebailey]

It looks like this bit was added:

        if (location.flags & NodeFlags.Ambient) {
            return; // References within types and declaration files are never going to contribute to retaining a JS import
        }

Which explicitly skips marking references for declare.