Description

Klemen Oslaj (klemenoslaj)

opened on Aug 1, 2019

Issue body actions

TypeScript Version: 3.6.0-dev.20190801

Search Terms:

• type assertion absolute import
• type assertion import
• type cast absolute import
• type cast import
• type assertion pick

Code

Repo: https://github.com/klemenoslaj/typescript-type-assertion

generated/types.d.ts

export interface TypeD {
  da: string;
  db: string;
  dc: string;
}

export interface Test { 
  a: string;
  b: string;
  c: string;
  d?: { __private: 'd' } & TypeD;
}

src/index.model.ts

import { Test } from 'generated/types';

type DType = NonNullable<Test['d']>;
export type Model = Pick<DType, keyof Exclude<DType, '__private'>>;

src/index.ts

import { Model } from './index.model';

export class A {
    value = <Model>{};
}

dist/index.model.d.ts

import { Test } from 'generated/types';
declare type DType = NonNullable<Test['d']>;
export declare type Model = Pick<DType, keyof Exclude<DType, '__private'>>;
export {};

dist/index.d.ts

export declare class A {
    value: Pick<{
        __private: "d";
    } & import("../generated/types").TypeD, "__private" | "da" | "db" | "dc">;
}

Expected behavior:

I would expect that dist/index.d.ts type definitions would result in:

import { Model } from './index.model';
export declare class A {
    value: Model;
}

In fact, this is the result of type definitions, if I change value = <Model>{}; to value: Model = <Model>{};.

Why doesn't typescript use Model directly when type asserting?

Actual behavior:

Results in:

export declare class A {
    value: Pick<{
        __private: "d";
    } & import("../generated/types").TypeD, "__private" | "da" | "db" | "dc">;
}

Playground Link:
I couldn't figure out how to compile declarations in playground, sorry :(

As an alternative please clone the following repo: https://github.com/klemenoslaj/typescript-type-assertion

Explanation:
This is quite a significant problem in monorepo environment.
What happens is that projects are compiled in the dist/ folder and they contain relative path like above (import("../generated/types")), which points from the src/ and not from dist/, effectively producing an error when projects start using one another.

Why doesn't typescript:

• use the original path from the import (generated/types)?
• use the type from assertion directly (Model)?

Reacted by Eugen Starov

Activity

1. dragomirtitian commented on Aug 1, 2019

   

   Titian Cernicova-Dragomir (dragomirtitian)

   on Aug 1, 2019

   Contributor

   More actions

   A generally feature of type aliases is that they can be expanded transparently by the compiler, so probably when you use the assertion the compiler does not think it needs to keep the name around.

   Using an interface will probably get you the effect you desire:

   export interface Model extends  Pick<DType, keyof Exclude<DType, '__private'>> {}
2. klemenoslaj commented on Aug 1, 2019

   

   Klemen Oslaj (klemenoslaj)

   on Aug 1, 2019

   Author

   More actions

   A generally feature of type aliases is that they can be expanded transparently by the compiler, so probably when you use the assertion the compiler does not think it needs to keep the name around.

   Using an interface will probably get you the effect you desire:

   export interface Model extends  Pick<DType, keyof Exclude<DType, '__private'>> {}

   Yes, that works 👍

   However, we cannot force people to use interfaces, therefore issue might still pop out causing frustrations, since it is not really straight forward problem.

   Is there any other way?

   EDIT

   Furthermore, if types are generated by 3rd party, we are even out of control, and using the type directly from generated/types will result in the same problem.

   I have update the repository accordingly:

   export class A {
       value1 = <Model>{};
       value2 = <Test['e']>{};
   }

   Results in

   export declare class A {
       value1: Pick<{
           __private: "d";
       } & import("../generated/types").TypeD, "__private" | "da" | "db" | "dc">;
       value2: {
           __private: "e";
       } & import("../generated/types").TypeD;
   }
3. Ryan Cavanaugh (RyanCavanaugh)

   added

   BugA bug in TypeScriptA bug in TypeScript

   on Aug 1, 2019
4. Ryan Cavanaugh (RyanCavanaugh)

   added this to the TypeScript 3.7.0 milestone on Aug 1, 2019
5. Ryan Cavanaugh (RyanCavanaugh)

   assigned

   Ryan Cavanaugh (RyanCavanaugh)

   and

   Wesley Wigham (weswigham)

   and unassigned

   Ryan Cavanaugh (RyanCavanaugh)

   on Aug 1, 2019
6. Ryan Cavanaugh (RyanCavanaugh)

   removed

   BugA bug in TypeScriptA bug in TypeScript

   on Aug 1, 2019
7. Ryan Cavanaugh (RyanCavanaugh)

   unassigned

   Wesley Wigham (weswigham)

   on Aug 1, 2019
8. Ryan Cavanaugh (RyanCavanaugh)

   removed this from the TypeScript 3.7.0 milestone on Aug 1, 2019
9. Ryan Cavanaugh (RyanCavanaugh)

   added

   BugA bug in TypeScriptA bug in TypeScript

   on Aug 1, 2019
10. Ryan Cavanaugh (RyanCavanaugh)

    added this to the TypeScript 3.7.0 milestone on Aug 1, 2019
11. Ryan Cavanaugh (RyanCavanaugh)

    assigned

    Wesley Wigham (weswigham)

    on Aug 1, 2019
12. Ryan Cavanaugh (RyanCavanaugh)

    modified the milestones: TypeScript 3.7.0, TypeScript 3.7.1 on Oct 14, 2019
13. Ryan Cavanaugh (RyanCavanaugh)

    modified the milestones: TypeScript 3.7.1, TypeScript 3.8.0 on Oct 29, 2019
14. Ryan Cavanaugh (RyanCavanaugh)

    modified the milestones: TypeScript 3.8.0, TypeScript 3.8.1 on Jan 8, 2020
15. Ryan Cavanaugh (RyanCavanaugh)

    unassigned

    Wesley Wigham (weswigham)

    on Jan 24, 2020
16. Ryan Cavanaugh (RyanCavanaugh)

    added

    Needs InvestigationThis issue needs a team member to investigate its status.This issue needs a team member to investigate its status.

    and removed

    BugA bug in TypeScriptA bug in TypeScript

    on Jan 24, 2020
17. Ryan Cavanaugh (RyanCavanaugh)

    modified the milestones: TypeScript 3.8.1, Backlog on Jan 24, 2020

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