A2 utility task to export schemas to A3 format

A command line task running in an A2 module that can "see" all of the schemas for all of the defined doc and widget types, their sub-array and object fields, et cetera.

The command to run in your A2 project will be:

node app apostrophe-a3-schema-exporter:export

Iterates over all of these and adds a schema.js file in the A3 format in every custom module. You can change the parent folder name of modules by passing the option --folder. By default, it is lib/modules. Example:

node app apostrophe-a3-schema-exporter:export --folder="src/lib/modules"

Pay attention, the script will overwrite existing schema.js files in your modules directories.

The directory structure would look like:

modules
  custom-module
    schema.js
  custom-page
    schema.js
  custom-widget
   schema.js

Inside each one the format would be:

module.exports = {
  ... a3 fields here
};

This makes it easy to pull into custom-module/index.js:

module.exports = {
  extend: '@apostrophecms/piece-type', // or whatever type needed as '@apostrophecms/piece-page-type' for example
  fields: require('./schema.js')
};

This greatly helps with A2 to A3 migration although manual review is required because it does not understand:

• Fields being optional based beforeConstruct logic
• Fields being inherited from a base class module like apostrophe-pieces, i.e. not necessary to redefine them in a subclass
• Fields being removed via removeFields
• Fields that no longer generally exist in A3, e.g. published
• apostrophecms-group is mapped to @apostrophecms/group but if @apostrophecms-pro/advanced-permission-group is necessary, it will be needed to handle this manually