Subclassing Help in a JavaScript project throws errors

[tarkatronic]

Steps to reproduce:

1. Create a new JavaScript project

   $ npx oclif multi test-command

2. Create test-command/src/help.js

    const { Help } = require('@oclif/plugin-help');
    
    module.exports = class TestHelp extends Help {
      showHelp(args) {
        console.log('Hello, world! I am customized help!');
        super.showHelp(args);
      }
    };

3. Add oclif.helpClass key to package.json:

   {
     "oclif": {
       "helpClass": "./src/help"
     }
   }

4. Run command:

   $ node bin/run
   Error: Unable to load configured help class "./src/help", failed with message:
   Class extends value undefined is not a constructor or null
       at Object.getHelpClass (~/workspace/test-command/node_modules/@oclif/plugin-help/lib/util.js:66:19)
       at Main._help (~/workspace/test-command/node_modules/@oclif/command/lib/main.js:40:41)
       at Main.init (~/workspace/test-command/node_modules/@oclif/command/lib/command.js:81:25)
       at Main.init (~/workspace/test-command/node_modules/@oclif/command/lib/main.js:12:22)
       at async Main._run (~/workspace/test-command/node_modules/@oclif/command/lib/command.js:42:13)

The documentation currently only shows extending HelpBase in JavaScript projects, although the second example appears to be showing an example which would be extending Help. If I change my example to extend HelpBase, it fails in a different yet predictable fashion:

$ node bin/run
Hello, world! I am customized help!
TypeError: (intermediate value).showHelp is not a function
    at TestHelp.showHelp (~/workspace/test-command/src/help.js:6:11)
    at Main._help (~/workspace/test-command/node_modules/@oclif/command/lib/main.js:42:14)
    at Main.init (~/workspace/test-command/node_modules/@oclif/command/lib/command.js:81:25)
    at Main.init (~/workspace/test-command/node_modules/@oclif/command/lib/main.js:12:22)
    at async Main._run (~/workspace/test-command/node_modules/@oclif/command/lib/command.js:42:13)

[childish-sambino]

Think this is similar to oclif/plugin-plugins#97. Temporary fix/hack is to pin tslib to 1.11.2.

[tarkatronic]

@childish-sambino Sadly, that had no effect. I still get the same errors, even with tslib pinned.

[tarkatronic]

I have found a solution to this thanks to @bcbailey. There seems to be a problem with the fact that the Help class is an export default, and we are using require(...). The fix was to change my code to:

const Help = require('@oclif/plugin-help').default;

And now I get the expected:

$ node bin/run
Hello, world! I am customized help!
VERSION
  test-command/0.0.0 linux-x64 node-v12.16.2

USAGE
  $ test-command [COMMAND]

COMMANDS
  hello  Describe the command here
  help   display help for test-command

[RasPhilCo]

Thanks for bringing this to our attention!