Creating a Typescript definition that includes a custom constant enumeration allows for precise

Question

Creating a Typescript definition that includes a custom constant enumeration allows for precise

Struggling to generate TypeScript definition files for a specific library.

The library contains a method that requires a parameter of type number, limited to a specific set of numbers. Therefore, I aim to specify in my definition that it necessitates an enum type created using a const enum.

However, upon defining my class within a .d.ts file like this:

// definitions/SimpleDefinition.d.ts

/// <reference path="Enums.ts" />

declare class SampleDefinedClass {
    public static SampleMethod(enumArg: Enums.SampleEnum): void;
}

I define my enum as follows:

// definitions/Enums.ts

export const enum SampleEnum {
    Item1 = 1,
    Item2 = 2
}

To link the two, I utilize an index.d.ts:

// definitions/index.d.ts

/// <reference path="Enums.ts" />
/// <reference path="SampleDefinition.d.ts" />

The compiler throws this error message:

../definitions/SampleDefinition.d.ts(4,41): error TS2503: Cannot find namespace 'Enums'.

I attempted adding an import statement at the beginning of my SampleDefinition.d.ts, but this led to the definition not being correctly identified in my code file, despite no errors shown by Visual Studio or Visual Studio Code for the import itself.

import Enums = require("./Enums");

Main.ts(6,1): error TS2304: Cannot find name 'SampleDefinedClass'.

Various attempts have been made, such as experimenting with AMD and relocating files, yet achieving functionality seems elusive. Is there a viable solution? Or must I resort to alternative methods or abandon the endeavor?

A Github repository showcasing this scenario can be found here.

typescript commonjs typescript-typings

Answer 1

Answer №1

The file SampleDefinition.d.ts lacks top-level import or export statements, whereas Enum.ts includes them. This means that Enums is considered a module, while SampleDefinition is not. However, there is an attempt to use Enums within it. In older terminology, SampleDefinition.d.ts is classified as an internal module and Enums as an external module. Mixing the two in one application is not allowed.

To resolve this inconsistency, there are two approaches:

One solution involves making everything internal without any top-level imports/exports:

In Enum.ts, enclose the export within a namespace:

namespace Enums {
    export const enum SampleEnum {
        Item1 = 1,
        Item2 = 2
    }
}

In Main.ts, simply remove the line import Enums ...:

/// <reference path="../definitions/index.d.ts" />

console.log(Enums.SampleEnum.Item2);
SampleDefinedClass.SampleMethod(Enums.SampleEnum.Item1);

Alternatively, convert everything into modules:

In SampleDefinition.ts, utilize import instead of reference and switch to exporting the class:

import Enums = require("./Enums");

export class SampleDefinedClass {
    public static SampleMethod(enumArg: Enums.SampleEnum): void;
}

In Main.ts, explicitly import all dependencies instead of using reference:

import Enums = require("../definitions/Enums");
import {SampleDefinedClass} from "../definitions/SampleDefinition"

console.log(Enums.SampleEnum.Item2);
SampleDefinedClass.SampleMethod(Enums.SampleEnum.Item1);

The choice between the two methods depends on your preference. The key distinction is that with modules, the app will need a module loader at runtime. Without modules, it can be compiled into a single script file. This primarily impacts browsers (where you must supply a module loader) as code compiled for Node.js will work with require regardless.

Answer 2

The file SampleDefinition.d.ts lacks top-level import or export statements, whereas Enum.ts includes them. This means that Enums is considered a module, while SampleDefinition is not. However, there is an attempt to use Enums within it. In older terminology, SampleDefinition.d.ts is classified as an internal module and Enums as an external module. Mixing the two in one application is not allowed.

To resolve this inconsistency, there are two approaches:

One solution involves making everything internal without any top-level imports/exports:

In Enum.ts, enclose the export within a namespace:

namespace Enums {
    export const enum SampleEnum {
        Item1 = 1,
        Item2 = 2
    }
}

In Main.ts, simply remove the line import Enums ...:

/// <reference path="../definitions/index.d.ts" />

console.log(Enums.SampleEnum.Item2);
SampleDefinedClass.SampleMethod(Enums.SampleEnum.Item1);

Alternatively, convert everything into modules:

In SampleDefinition.ts, utilize import instead of reference and switch to exporting the class:

import Enums = require("./Enums");

export class SampleDefinedClass {
    public static SampleMethod(enumArg: Enums.SampleEnum): void;
}

In Main.ts, explicitly import all dependencies instead of using reference:

import Enums = require("../definitions/Enums");
import {SampleDefinedClass} from "../definitions/SampleDefinition"

console.log(Enums.SampleEnum.Item2);
SampleDefinedClass.SampleMethod(Enums.SampleEnum.Item1);

The choice between the two methods depends on your preference. The key distinction is that with modules, the app will need a module loader at runtime. Without modules, it can be compiled into a single script file. This primarily impacts browsers (where you must supply a module loader) as code compiled for Node.js will work with require regardless.

Answer 3

Answer №2

When exporting enums in a definition file, remember to use declare.

I found some examples on DefinitelyTyped, like this one:

export declare enum EDeflateStrategy {
    DEFAULT_STRATEGY = 0,
    FILTERED = 1,
    HUFFMAN_ONLY = 2,
    RLE = 3,
    FIXED = 4,
}

The issue with your code lies in the fact that your definition file appears to be referencing a .ts file instead of a .d.ts file.

If you own the library and it's written in TypeScript, simply add

"declaration": true

to your tsconfig.json file and let tsc generate the definitions for you.

If it's not yours, you can try mocking things from the library in TypeScript and allow tsc to create declarations by enabling this option.

Answer 4

When exporting enums in a definition file, remember to use declare.

I found some examples on DefinitelyTyped, like this one:

export declare enum EDeflateStrategy {
    DEFAULT_STRATEGY = 0,
    FILTERED = 1,
    HUFFMAN_ONLY = 2,
    RLE = 3,
    FIXED = 4,
}

The issue with your code lies in the fact that your definition file appears to be referencing a .ts file instead of a .d.ts file.

If you own the library and it's written in TypeScript, simply add

"declaration": true

to your tsconfig.json file and let tsc generate the definitions for you.

If it's not yours, you can try mocking things from the library in TypeScript and allow tsc to create declarations by enabling this option.

Creating a Typescript definition that includes a custom constant enumeration allows for precise

Answer №1

Answer №2

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