Bringing in an interface that has been declared using export = alongside an ambient module

Question

Bringing in an interface that has been declared using export = alongside an ambient module

When working with a Typescript module, it is possible to import various exports including classes, interfaces, variables and enums that were exported using the old export = syntax.

However, I have noticed that when attempting this with an ambient module, the compiler (version 1.8.10) does not seem to recognize the import statement.

Declaration File:

//Module declaration
declare module "foo" {
    interface barProc {
        (): any;
    }

    //Note: if I use the function equivalent to the interface this works ok.    
    function worksOk(): any;

    export = barProc;
}

Main File:

//Module usage 
import myFunc = require("foo");
myFunc();

In this scenario, the compiler raises an error stating that myFunc is an unknown identifier and the import line doesn't show up in the output Javascript file.

Note: Although in the example illustrated, no other members are added to the interface for simplicity reasons, the interface is used because the JavaScript library being modeled has members on the function.

Is there anything wrong with how I'm doing this, or is there a workaround available?

typescript

Answer 1

Answer №1

barProc is defined as an interface, making it a type rather than a variable of that type. While you can export and utilize it as a type in other parts of your code, you cannot directly invoke it as a function like in the sample provided.

The sample given can be likened to:

interface barProc {
    (): any;
}

barProc();

When presented this way, it becomes evident that it is incorrect. A correct approach would be more along the lines of:

interface barProc {
    (): any;
}

var myFunc: barProc;

myFunc();

Transforming this into a module structure would result in:

declare module "foo" {
    interface barProc {
        (): any;
    }

    var myFunc: barProc;

    export = myFunc;
}


// Usage in another part of the code:

import myFunc = require("foo");
myFunc();

By following this pattern, you should achieve the desired outcome.

Answer 2

barProc is defined as an interface, making it a type rather than a variable of that type. While you can export and utilize it as a type in other parts of your code, you cannot directly invoke it as a function like in the sample provided.

The sample given can be likened to:

interface barProc {
    (): any;
}

barProc();

When presented this way, it becomes evident that it is incorrect. A correct approach would be more along the lines of:

interface barProc {
    (): any;
}

var myFunc: barProc;

myFunc();

Transforming this into a module structure would result in:

declare module "foo" {
    interface barProc {
        (): any;
    }

    var myFunc: barProc;

    export = myFunc;
}


// Usage in another part of the code:

import myFunc = require("foo");
myFunc();

By following this pattern, you should achieve the desired outcome.

Bringing in an interface that has been declared using export = alongside an ambient module

Answer №1

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