typescript: How to extend existing module definition?

Question

I have a declaration file written for extsting npm package, but seems like one method was not declared, I try to declare it, but get an error. Help me please.

structure of existing d.ts file:

declare module "mongoose" {
...
  class Document {}
  interface Document extends MongooseDocument, NodeJS.EventEmitter, ModelProperties {
    increment(): this;
    remove(fn?: (err: any, product: this) => void): Promise<this>;
    ...
  }
}

I try to add to interface Document method deleteOne. My custom.d.ts:

declare module "mongoose" {
  interface Document {
    deleteOne(fn?: (err: any, product: this) => void): Promise<this>;
  }
}

But still I get an error "Property 'deleteOne' does not exist on type".

Here is my tsconfig.json if you need:

{
    "compilerOptions": {
      "module": "commonjs",
      "removeComments": true,
      "esModuleInterop": true,
      "moduleResolution": "node",
      "allowJs": true,
      "allowSyntheticDefaultImports": true,
      "pretty": true,
      "resolveJsonModule": true,
      "sourceMap": true,
      "target": "ES2018",
      "outDir": "dist",
      "baseUrl": ".",
      "paths": {
          "*": [
              "node_modules/*"
          ]
      }
    },
    "include": [
      "src/**/*"
    ],
    "exclude": [
      "node_modules",
      "dist",
      "**/*.spec.ts"
    ]
  }

My custom.d.ts file located in 'src/' dir.

Can you not use the standard @types/mongoose in your code? npmjs.com/package/@types/mongoose — paperba1l
– paperba1l, Commented Feb 3, 2020 at 21:53
@skyhavoc it is already @types/mongoose. And also it is important to me to learn how to declare, not just use module — Maxim
– Maxim, Commented Feb 4, 2020 at 5:51
Could it be because your document interface is not extending? interface Document extends MongooseDocument, NodeJS.EventEmitter, ModelProperties? — hazardous
– hazardous, Commented Feb 4, 2020 at 11:25
@hazardous I tried to extend, but got the same result - error — Maxim
– Maxim, Commented Feb 4, 2020 at 11:26

d9k · Accepted Answer · 2023-03-22 09:09:27Z

25

I had to use reexport in my case to merge declarations. typescript 4.0.5

global-axios.d.ts:

export * from 'axios';

declare module 'axios' {
    export interface AxiosRequestConfig {
        myConfigOption?: boolean;
    }
}

answered Mar 22, 2023 at 9:09

d9k

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1 Comment

Stefanie Over a year ago

Awesome! This worked great for me as well. Needed to add a missing type for mixpanel.

Henry · Accepted Answer · 2023-01-06 00:23:24Z

5

OK! Now I know this is expected behavior of ts-node: https://github.com/TypeStrong/ts-node#missing-types

I have configured paths settings in tsconfig.json, and now everything is working:

    "paths": {
        "mongoose": ["src/custom.d.ts"],
        "*": [
            "node_modules/*"
        ]
    }

edited Jan 6, 2023 at 0:23

Henry

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answered Feb 10, 2020 at 8:02

Maxim

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Comments

paperba1l · Accepted Answer · 2020-02-04 15:28:42Z

1

defining the Mongoose interface

// types/mongoose/index.d.ts
declare module 'mongoose' {
  namespace Mongoose {
    export interface MyInterface {
      name: number;
    }
  }
}

usage

// app.ts
import mongoose, { Mongoose } from 'mongoose';
const a: Mongoose.MyInterface = {
  name: 122
};

I have also added "typeRoots": ["./node_modules/@types", "./server/types"], to my tsconfig file

does this help

answered Feb 4, 2020 at 15:28

paperba1l

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1 Comment

Maxim Over a year ago

it is not worked, but it was a good hint to me - to change my tsconfic file

Stefan Mares · Accepted Answer · 2025-05-02 10:50:31Z

0

In my case, there were two files named the same: theme.ts and theme.d.ts, and changing theme.d.ts to something different worked. 🤷

answered May 2 at 10:50

Stefan Mares

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