# Introduction
This PR aims to deprecate having to manually handle optimistic side
effect foreign key addition in the whole v2 experience.
This PR implements the strong basis + builder refactor of the optimistic
computation of a given flat entity maps with its related flat entity
maps ( runner needs a small refactor on actions type definition first )
Flat entity maps updates through mutations are now only scoped to the
generic entity builder ( very isolated )
## What's next
- Refactor actions v2 type definition to gain grain over `metadataName`
and action operation ( `create` `delete` `update` ).
from `{type: 'create_view_field'}` to `{metadataName: 'view_field',
type: 'create' }`
- Use new optimistic tool computation tools
- Only invalidate impacted flat maps cache
## New tools
Strictly dynamically typed new flat entity maps tools
- `addFlatEntityToFlatEntityAndRelatedEntityMapsThroughMutationOrThrow`
-
`deleteFlatEntityFromFlatEntityAndRelatedEntityMapsThroughMutationOrThrow`
## Unit test
Adding basic unit testing coverage to introduced tools
## `FlatEntityValidationArgs`
From
```ts
export type FlatEntityValidationArgs<T extends AllMetadataName> = {
flatEntityToValidate: MetadataFlatEntity<T>;
optimisticFlatEntityMaps: MetadataFlatEntityMaps<T>;
mutableDependencyOptimisticFlatEntityMaps: MetadataValidationRelatedFlatEntityMaps<T>;
workspaceId: string;
remainingFlatEntityMapsToValidate: MetadataFlatEntityMaps<T>;
buildOptions: WorkspaceMigrationBuilderOptions;
};
```
To
```ts
export type FlatEntityValidationArgs<T extends AllMetadataName> = {
flatEntityToValidate: MetadataFlatEntity<T>;
optimisticFlatEntityMapsAndRelatedFlatEntityMaps: MetadataFlatEntityAndRelatedFlatEntityMapsForValidation<T>;
workspaceId: string;
remainingFlatEntityMapsToValidate: MetadataFlatEntityMaps<T>;
buildOptions: WorkspaceMigrationBuilderOptions;
};
```
