Confusing error message in elm reactor when missing main

[brainrake]

Quick Summary: When loading a module without a main function from elm reactor, the following error message is displayed:

Initialization Error

ReferenceError: _Platform_export is not defined

A better message would include a hint, eg.

Did you forget to define a main value?

SSCCE

module Main exposing (..)

a = 0

• Elm: 0.19.1
• Browser: *
• Operating System: *

Additional Information:

Running elm make on a file with no main results in a great error message.

edit: clarify, add additional information

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[jessbowers]

This makes elm reactor confusing for beginners. That's what i'm experiencing now. There isn't easy documentation about getting started with reactor to begin with -- it's a little too simple in the guide. I don't know what to expect when pointing at my "non-main" elm module file. So this change would help that, IMO.

[nilslindemann]

Actually I like that oneliner in the docs: "use elm reactor". How could it be simpler? And what would you need more? "For more info use elm --help"?

[meltingscales]

Just found this thread, thank god - Learning Elm, this error is extremely confusing - Perhaps a warning can be thrown sometime during compilation?