# Introduction
In this PR we catch all the runner errors coming from a single workspace
migration action execution.
**1. `WorkspaceMigrationActionExecutionException`** (low-level,
action-specific)
- Thrown from action handlers, utils, and helper functions
- Contains specific error codes: `FIELD_METADATA_NOT_FOUND`,
`OBJECT_METADATA_NOT_FOUND`, `ENUM_OPERATION_FAILED`, `NOT_SUPPORTED`,
etc.
- Simple structure: `message`, `code`, `userFriendlyMessage`
- No action context - just describes what went wrong
**2. `WorkspaceMigrationRunnerException`** (high-level, runner-scoped)
- Only two codes: `INTERNAL_SERVER_ERROR` and `EXECUTION_FAILED`
- `EXECUTION_FAILED` **requires** `action` + `errors` (contains the
action context)
- `INTERNAL_SERVER_ERROR` **requires** `message` (no action context)
## Refactor
- Removed the `relatedFlatEntityMapsKeys` from the `WorkspaceMigration`
type as they're directly inferred from passed actions
- Swallowing actions rollbacks errors in order to iterate over all of
them
## Testing
Created a very straigthforward install application from workspace
migration endpoint in order to start testing the introduced
`WorkspaceMigrationActionExecutionException`
Introduced a feature flag that stop the access to the endpoint if not
enabled
Whole taken direction are totally subjective and highly prone to
mutations ( endpoint location, naming and input schema see
`ts-expect-error` comment )
cc @martmull
## Response error
```ts
{
"eventId": "evt_a1b2c3d4-5678-90ab-cdef-1234567890ab",
"extensions": {
"action": {
"metadataName": "fieldMetadata",
"type": "delete",
"universalIdentifier": "20202020-6110-4547-9fd0-2525257a2c3f"
},
"code": "APPLICATION_INSTALLATION_FAILED",
"errors": {
"metadata": {
"code": "ENTITY_NOT_FOUND",
"message": "Could not find flat entity with universal identifier 20202020-6110-4547-9fd0-2525257a2c3f"
},
"workspaceSchema": {
"code": "ENTITY_NOT_FOUND",
"message": "Could not find flat entity in maps"
}
},
"exceptionEventId": "exc_f9e8d7c6-5432-10ba-fedc-ba0987654321",
"userFriendlyMessage": "Migration execution failed."
},
"message": "Migration action 'delete' for 'fieldMetadata' failed",
"name": "GraphQLError"
}
```
As part of the extensibility effort, we are introducing a new engine
entity called "Front Component". This represents a dynamic react
component that will be rendered in CommandMenu actions or in PageLayout
widgets
This PR introduce the entity and all the necessary boilerplate to make
it syncable and cachable in the engine
Raphaël Bosi