Local plugin not being loaded

[jugglingcats]

Hi, am trying to develop a simple local plugin in my gatsby project. The steps I've taken are:

1. Created new project using all defaults

npm init gatsby

2. Added plugins/gatsby-plugin-simple with index.js as follows (in desperate attempt to get something output!)

console.error("PLUGIN LOADED!!")
throw new Error("EXIT POINT 1")

exports.onPreInit = () => {
    console.error("PLUGIN PRE-INIT!!")
    throw new Error("EXIT POINT 2")
}

3. Added plugin to gatsby-config.js:

module.exports = {
    siteMetadata: {
        siteUrl: `https://www.yourdomain.tld`,
    },
    plugins: [
        "gatsby-plugin-simple"
    ]
}

Project structure:

Running npm run develop produces the following:

success open and validate gatsby-configs, load plugins - 0.191s
success onPreInit - 0.002s
success initialize cache - 0.074s
success copy gatsby files - 0.179s
success Compiling Gatsby Functions - 0.369s

If I deliberately misspell the plugin name in gatsby-config.js it gives an error, so I know it is resolving the plugin!

Output from gatsby info:

  System:
    OS: Windows 10 10.0.19043
    CPU: (12) x64 Intel(R) Core(TM) i7-8750H CPU @ 2.20GHz
  Binaries:
    Node: 14.17.3 - D:\Program Files\nodejs\node.EXE
    Yarn: 1.22.10 - D:\Program Files\nodejs\yarn.CMD
    npm: 6.14.4 - D:\Program Files\nodejs\npm.CMD
  Languages:
    Python: 3.9.6 - /c/Python39/python
  Browsers:
    Chrome: 93.0.4577.82
    Edge: Spartan (44.19041.1023.0), Chromium (93.0.961.52)
  npmPackages:
    gatsby: ^3.13.1 => 3.14.0 
  npmGlobalPackages:
    gatsby-cli: 3.0.0

Any help much appreciated, am at a bit of a loss.

[jugglingcats]

[hgb123]

(moved to this answer)

[jugglingcats]

Thank you that worked! There should be a mention in the docs, or even better Gatsby should use the main from package.json, imho.

I can't see how to mark your reply as the accepted answer...

[hgb123]

@jugglingcats I'll post that in a separate answer

[hgb123]

you should remove index.js and add gatsby-node.js instead, with the same content

// plugins/gatsby-plugin-simple/gatsby-node.js

console.error("PLUGIN LOADED!!")
throw new Error("EXIT POINT 1")

exports.onPreInit = () => {
    console.error("PLUGIN PRE-INIT!!")
    throw new Error("EXIT POINT 2")
}

and the plugins/gatsby-plugin-simple/package.json should be like

{
  "name": "gatsby-plugin-simple",
  ...
}