migrate-virtual-fields

name	migrate-virtual-fields
description	Migrate Keystone virtual fields to OpenSaaS Stack format. Invoke as a forked subagent when virtual fields are detected, passing the config file path and field details as arguments.
context	fork
agent	general-purpose

Migrate the virtual fields described below to OpenSaaS Stack format. OpenSaaS Stack has no GraphQL — virtual fields use hooks.resolveOutput with a type declaration instead of graphql.field().

$ARGUMENTS

Migration Pattern

For every virtual field, apply this transformation:

Before (Keystone):

import { graphql } from '@keystone-6/core'

fieldName: virtual({
  field: graphql.field({
    type: graphql.String, // or graphql.Int, graphql.Boolean, etc.
    resolve: (item, args, context) => someValue,
  }),
})

After (OpenSaaS Stack):

fieldName: virtual({
  type: 'string', // see type mapping below
  hooks: {
    resolveOutput: ({ item, context }) => someValue,
  },
})

Type Mapping

Keystone graphql.*	OpenSaaS type
graphql.String	'string'
graphql.Int / graphql.Float	'number'
graphql.Boolean	'boolean'
graphql.list(graphql.String)	'string[]'
Custom object type	{ value: MyClass, from: 'package-name' }

For custom/imported types (e.g. Decimal):

import Decimal from 'decimal.js'

totalPrice: virtual({
  type: { value: Decimal, from: 'decimal.js' },
  hooks: {
    resolveOutput: ({ item }) => new Decimal(item.price).times(item.quantity),
  },
})

Context Queries Inside resolveOutput

If the original resolve used context.query.* or context.db.*, replace with context.db.*:

// Before
resolve: async (item, _, context) => {
  return context.query.Post.count({ where: { author: { id: { equals: item.id } } } })
}

// After
resolveOutput: async ({ item, context }) => {
  return context.db.post.count({ where: { authorId: { equals: item.id } } })
}

Steps

1. Read the config file to find all virtual() field definitions
2. For each virtual field: a. Identify the graphql.* type → map to the OpenSaaS type value b. Extract the resolve function body c. Rewrite as hooks: { resolveOutput: ({ item, context }) => ... } d. Replace any context.query.* calls with context.db.* equivalents e. Note: field arguments (args) are NOT supported — if the original used args, bake in a default or split into multiple fields
3. After all virtual fields are updated, remove any graphql imports from @keystone-6/core that are no longer used
4. Report: list each field that was changed and what the new definition looks like