Expression is not callable in 4.0.0

[marluanespiritusanto]

After updating to 4.0.0 version the helmet middleware configuration throws an error:

This expression is not callable.
 Type 'typeof import("/node_modules/helmet/dist/index")' has no call signatures.ts(2349)

This is the code Im trying to run:

import * as helmet from 'helmet';
import * as express from "express";

const app = express();

// express middleware configuration
app.use(helmet())

[EvanHahn]

What does your tsconfig.json look like, if you can share it?

[marluanespiritusanto]

@EvanHahn Here it is

{
  "compilerOptions": {
    "paths": {
      "@modules/*": ["./src/modules/*"],
      "@database/*": ["./src/database/*"],
      "@common/*": ["./src/common/*"],
      "@utils/*": ["./src/utils/*"]
    },
    "module": "commonjs",
    "declaration": true,
    "removeComments": true,
    "emitDecoratorMetadata": true,
    "experimentalDecorators": true,
    "allowSyntheticDefaultImports": true,
    "target": "es2017",
    "sourceMap": true,
    "outDir": "./dist",
    "baseUrl": "./",
    "incremental": true
  }
}

[EvanHahn]

Would you be willing to enable esModuleInterop, if that fixes your problem?

[hongbo-miao]

Hi @marluanespiritusanto My upgrading experience was smooth. I just upgraded to helmet 4.0.0, the code is at https://github.com/Hongbo-Miao/hongbomiao.com/blob/master/server/src/security/middlewares/helmet.middleware.ts
tsconfig.json is at https://github.com/Hongbo-Miao/hongbomiao.com/blob/master/server/tsconfig.json

I am using "module": "esnext", but I also succeed on "module": "commonjs".
See if my tsconfig.json helps locate the issue.

[joshuajung]

I'm facing the same issue, and unfortunately esModuleInterop does not seem to fix it - still getting the no call signatures error. My full tsconfig.json, with TS 3.9.7:

{
  "compilerOptions": {
    "module": "commonjs",
    "declaration": true,
    "removeComments": true,
    "emitDecoratorMetadata": true,
    "experimentalDecorators": true,
    "target": "es2017",
    "sourceMap": true,
    "outDir": "./dist",
    "baseUrl": "./src",
    "incremental": true,
    "strict": true,
    "esModuleInterop": true,
  },
  "exclude": ["node_modules", "dist"]
}

[anthony-telljohann]

I was able to resolve this by ignoring typescript errors before using helmet

import * as helmet from 'helmet'
...
// @ts-ignore
app.use(helmet(helmetConfig))

I believe this is because the default helmet export has an incorrectly defined type.

[EvanHahn]

I'd like to fix the Helmet types.

Helmet is a CommonJS module (in other words, it uses module.exports and not export ...). Therefore, without esModuleInterop, I would expect users to do something like this:

import helmet = require("helmet");

Though I'm not an expert at how TypeScript modules work.

[EvanHahn]

This issue looks the same as #235, so I'm going to close this issue and move discussion there.