Error: Attempt to change mapping for "form" extension from "application/x-www-form-urlencoded" to "application/x-www-form-urlencoded".

[sdesalas]

Superagent has recently been upgraded to use version 2.0.3 of mime.

However, between version 1.4.1 and 2.0.3 of mime an earlier warning has been upgraded to an error when defining the same mime types twice .

And since many other packages and tools rely on superagent, the lack of pre-check before defining mime-types a second time is causing subsequent require("superagent") calls from erroring out as per the example below (whenever two packages feature superagent as a dependency).

Use following steps to reproduce the error.

npm install swagger-tools supertest
node -e 'require("swagger-tools"); require("supertest");'

And the output:

/home/user/projects/mytest/node_modules/mime/Mime.js:32
          throw new Error(`Attempt to change mapping for "${ext}" extension from "${this._types[ext]}" to "${type}". Pass \`force=true\` to allow this, otherwise remove "${ext}" from the list of extensions for "${type}".`);
          ^

Error: Attempt to change mapping for "form" extension from "application/x-www-form-urlencoded" to "application/x-www-form-urlencoded". Pass `force=true` to allow this, otherwise remove "form" from the list of extensions for "application/x-www-form-urlencoded".
    at Mime.define (/home/user/projects/mytest/node_modules/mime/Mime.js:32:17)
    at Object.<anonymous> (/home/user/projects/mytest/node_modules/supertest/node_modules/superagent/lib/node/index.js:71:6)
    at Module._compile (module.js:569:30)
    at Object.Module._extensions..js (module.js:580:10)
    at Module.load (module.js:503:32)
    at tryModuleLoad (module.js:466:12)
    at Function.Module._load (module.js:458:3)
    at Module.require (module.js:513:17)
    at require (internal/module.js:11:18)
    at Object.<anonymous> (/home/user/projects/mytest/node_modules/supertest/lib/test.js:5:15)

[sdesalas]

Mime version 2.0.0 onwards provides a force=true flag to allow multiple calls to .define() for the same mime type, which in turn stops the error from being thrown.

Fix as follows:

/lib/node/index.js L71

/**
 * Define "form" mime type.
 */

mime.define({
  'application/x-www-form-urlencoded': ['form', 'urlencoded', 'form-data']
}, true); // <--- add 'force=true' here 

[allanyego]

I believe this is fixed for superagent but somehow I still get this error when using supertest to hit my endpoints. This was ok just yesterday, then today it's not working... Can anyone help here or is this an issue for supertest?

[leemr]

Based on this, https://github.com/strongloop/loopback-next/issues/6616, I updated loopback-connector-rest from ^3 to ^4.0.1. It has the fix for mime force=true.