restart api does not allow updating the env variables

What's going wrong?

When using the pm2 api restart gives and error and it does not update the environment variables although the documentation states it should do it.

How could we reproduce this issue?

Create a test.js file:

console.log(process.env.MY_ENV);

Create an app.js file:

const pm2 = require("pm2");

pm2.start(
  {
    name: "test",
    script: "./test.js",
    env: {
      MY_ENV: "test",
    },
  },
  function (err, apps) {
    if (err) {
      console.error(err);
      return pm2.disconnect();
    } else {
      console.log("Service test started.");

      pm2.restart(
        "test",
        {
          updateEnv: true,
          env: {
            MY_ENV: "restarted",
          },
        },
        function (err) {
          if (err) {
            console.error(err);
          } else {
            console.log("Service test restarted");
          }
        }
      );
    }
  }
);

run with:

$ node app.js

Produces this error:

Error: Using --env [env] without passing the ecosystem.config.js does not work
    at Object.Common.retErr (/Users/manuelastudillo/Dev/taskforce/taskforce-backend/config_app/node_modules/pm2/lib/Common.js:326:10)
    at API.restart (/Users/manuelastudillo/Dev/taskforce/taskforce-backend/config_app/node_modules/pm2/lib/API.js:519:31)

Using the option "env_" instead as suggested by the documentation avoids the error but the envs are not updated.

Supporting information

pm2 version 3.5.2

Start by running the provided app.js and test.js reproduction with PM2 3.5.2, then inspect the restart path referenced in lib/API.js and the error in lib/Common.js. Done means pm2.restart accepts the supplied environment options without the error and the restarted process reports MY_ENV as "restarted".