Custom Fields not showing in version 4.0.0

OS: macOS Catalina Version 10.15.7
Database: Postgres
Strapi version: 4.0.0

Hello, I’ve been using custom fields in Strapi 3.x.x, today I upgraded project to Strapi 4.0 and custom fields stopped working, it just renders disabled input as shown on screenshot.

Back then I pretty much followed this guide

After Strapi upgrade I copied my plugins from ~/plugins into ~/src/plugins then changed ~/config/plugins.js config as:

module.exports = ({ env }) => ({
  // ...
  "line-items": {
    enabled: true,
    resolve: './src/plugins/line-items'
  // ...

And in ~/src/api/order/content-types/order/schema.json I put:

"lineItems": {
      "type": "lineItems"

But no luck. Anyone has an idea what I’m missing? I tried new plugin via Strapi cli with just some “Hello World” rendering, but same result. Thank you for any help.

Edit: I found out, that in plugins created via Strapi CLI there is no registerField function as it was in v 3.x.x where the field registration was done by: strapi.registerField({ type: "lineItems", Component: LineItems });. Where can I find this function?

Figured out.

app.addFields({ type: 'lineItems', Component: MyComponent });`

Were you able to make this approach work?
I use the addFields and added the field in schema.json like:

  "attributes": {
    "fieldName": {
      "type": "customType"

the UI works but later after save data is not being record in db and just getting null.

Even tried with

<Component value={value} onChange={value => onChange({ target: { name, value, type: 'string', } })} .../>

Hey all, I just found this topic after posting this: Custom field interface for data entry - #3 by grafatim

Has anyone figured out how to get the SQL table to update to match the schema.json? The docs for this are non-existent and I’d love to help figure it out and then document!

I have opened an issue for this, in case anyone is interested: Issue storing data from Custom Fields in v4.x · Issue #12145 · strapi/strapi · GitHub