Syncable Entity: Builder & Validation (Step 3/6)

Purpose: Implement business rule validation and create migration action builders.

When to use: After completing Steps 1-2 (Types, Cache, Transform). Required before implementing action handlers.

---

Quick Start

This step creates:

1. Validator service (business logic validation)
2. Builder service (action creation)
3. Orchestrator wiring (CRITICAL - often forgotten!)

Key principles:

• Validators never throw - return error arrays
• Validators never mutate - pass optimistic entity maps
• Use indexed lookups (O(1)) not Object.values().find() (O(n))

---

Step 1: Create Validator Service

File: src/engine/workspace-manager/workspace-migration/workspace-migration-builder/validators/services/flat-my-entity-validator.service.ts

import { Injectable } from '@nestjs/common';
import { t, msg } from '@lingui/macro';
import { isDefined } from 'twenty-shared/utils';

import { type FlatMyEntity } from 'src/engine/metadata-modules/flat-my-entity/types/flat-my-entity.type';
import { type FlatMyEntityMaps } from 'src/engine/metadata-modules/flat-my-entity/types/flat-my-entity-maps.type';
import { WorkspaceMigrationValidationError } from 'src/engine/workspace-manager/workspace-migration/workspace-migration-builder/validators/types/workspace-migration-validation-error.type';
import { MyEntityExceptionCode } from 'src/engine/metadata-modules/my-entity/exceptions/my-entity-exception-code.enum';

@Injectable()
export class FlatMyEntityValidatorService {
  validateMyEntityForCreate(
    flatMyEntity: FlatMyEntity,
    optimisticFlatMyEntityMaps: FlatMyEntityMaps,
  ): WorkspaceMigrationValidationError[] {
    const errors: WorkspaceMigrationValidationError[] = [];

    // Pattern 1: Required field validation
    if (!isDefined(flatMyEntity.name) || flatMyEntity.name.trim() === '') {
      errors.push({
        code: MyEntityExceptionCode.NAME_REQUIRED,
        message: t`Name is required`,
        userFriendlyMessage: msg`Please provide a name for this entity`,
      });
    }

    // Pattern 2: Uniqueness check - use indexed map (O(1))
    const existingEntityWithName = optimisticFlatMyEntityMaps.byName[flatMyEntity.name];

    if (isDefined(existingEntityWithName) && existingEntityWithName.id !== flatMyEntity.id) {
      errors.push({
        code: MyEntityExceptionCode.MY_ENTITY_ALREADY_EXISTS,
        message: t`Entity with name ${flatMyEntity.name} already exists`,
        userFriendlyMessage: msg`An entity with this name already exists`,
      });
    }

    // Pattern 3: Foreign key validation
    if (isDefined(flatMyEntity.parentEntityId)) {
      const parentEntity = optimisticFlatParentEntityMaps.byId[flatMyEntity.parentEntityId];

      if (!isDefined(parentEntity)) {
        errors.push({
          code: MyEntityExceptionCode.PARENT_ENTITY_NOT_FOUND,
          message: t`Parent entity with ID ${flatMyEntity.parentEntityId} not found`,
          userFriendlyMessage: msg`The specified parent entity does not exist`,
        });
      } else if (isDefined(parentEntity.deletedAt)) {
        errors.push({
          code: MyEntityExceptionCode.PARENT_ENTITY_DELETED,
          message: t`Parent entity is deleted`,
          userFriendlyMessage: msg`Cannot reference a deleted parent entity`,
        });
      }
    }

    // Pattern 4: Standard entity protection
    if (flatMyEntity.isCustom === false) {
      errors.push({
        code: MyEntityExceptionCode.STANDARD_ENTITY_CANNOT_BE_CREATED,
        message: t`Cannot create standard entity`,
        userFriendlyMessage: msg`Standard entities can only be created by the system`,
      });
    }

    return errors;
  }

  validateMyEntityForUpdate(
    flatMyEntity: FlatMyEntity,
    updates: Partial<FlatMyEntity>,
    optimisticFlatMyEntityMaps: FlatMyEntityMaps,
  ): WorkspaceMigrationValidationError[] {
    const errors: WorkspaceMigrationValidationError[] = [];

    // Standard entity protection
    if (flatMyEntity.isCustom === false) {
      errors.push({
        code: MyEntityExceptionCode.STANDARD_ENTITY_CANNOT_BE_UPDATED,
        message: t`Cannot update standard entity`,
        userFriendlyMessage: msg`Standard entities cannot be modified`,
      });
      return errors; // Early return if standard
    }

    // Uniqueness check for name changes
    if (isDefined(updates.name) && updates.name !== flatMyEntity.name) {
      const existingEntityWithName = optimisticFlatMyEntityMaps.byName[updates.name];

      if (isDefined(existingEntityWithName) && existingEntityWithName.id !== flatMyEntity.id) {
        errors.push({
          code: MyEntityExceptionCode.MY_ENTITY_ALREADY_EXISTS,
          message: t`Entity with name ${updates.name} already exists`,
          userFriendlyMessage: msg`An entity with this name already exists`,
        });
      }
    }

    return errors;
  }

  validateMyEntityForDelete(
    flatMyEntity: FlatMyEntity,
  ): WorkspaceMigrationValidationError[] {
    const errors: WorkspaceMigrationValidationError[] = [];

    // Standard entity protection
    if (flatMyEntity.isCustom === false) {
      errors.push({
        code: MyEntityExceptionCode.STANDARD_ENTITY_CANNOT_BE_DELETED,
        message: t`Cannot delete standard entity`,
        userFriendlyMessage: msg`Standard entities cannot be deleted`,
      });
    }

    return errors;
  }
}

Performance warning: Avoid Object.values().find() - use indexed maps instead!

// ❌ BAD: O(n) - slow for large datasets
const duplicate = Object.values(optimisticFlatMyEntityMaps.byId).find(
  (entity) => entity.name === flatMyEntity.name && entity.id !== flatMyEntity.id
);

// ✅ GOOD: O(1) - use indexed map
const existingEntityWithName = optimisticFlatMyEntityMaps.byName[flatMyEntity.name];
if (isDefined(existingEntityWithName) && existingEntityWithName.id !== flatMyEntity.id) {
  // Handle duplicate
}

---

Step 2: Create Builder Service

File: src/engine/workspace-manager/workspace-migration/workspace-migration-builder/builders/my-entity/workspace-migration-my-entity-actions-builder.service.ts

import { Injectable } from '@nestjs/common';

import { WorkspaceEntityMigrationBuilderService } from 'src/engine/workspace-manager/workspace-migration/workspace-migration-builder/workspace-entity-migration-builder.service';
import { FlatMyEntityValidatorService } from 'src/engine/workspace-manager/workspace-migration/workspace-migration-builder/validators/services/flat-my-entity-validator.service';
import { type UniversalFlatMyEntity } from 'src/engine/workspace-manager/workspace-migration/universal-flat-entity/types/universal-flat-my-entity.type';
import {
  type UniversalCreateMyEntityAction,
  type UniversalUpdateMyEntityAction,
  type UniversalDeleteMyEntityAction,
} from 'src/engine/workspace-manager/workspace-migration/workspace-migration-builder/builders/my-entity/types/workspace-migration-my-entity-action.type';

@Injectable()
export class WorkspaceMigrationMyEntityActionsBuilderService extends WorkspaceEntityMigrationBuilderService<
  'myEntity',
  UniversalFlatMyEntity,
  UniversalCreateMyEntityAction,
  UniversalUpdateMyEntityAction,
  UniversalDeleteMyEntityAction
> {
  constructor(
    private readonly flatMyEntityValidatorService: FlatMyEntityValidatorService,
  ) {
    super();
  }

  protected buildCreateAction(
    universalFlatMyEntity: UniversalFlatMyEntity,
    flatEntityMaps: AllFlatEntityMapsByMetadataName,
  ): BuildWorkspaceMigrationActionReturnType<UniversalCreateMyEntityAction> {
    const validationResult = this.flatMyEntityValidatorService.validateMyEntityForCreate(
      universalFlatMyEntity,
      flatEntityMaps.flatMyEntityMaps,
    );

    if (validationResult.length > 0) {
      return {
        status: 'failed',
        errors: validationResult,
      };
    }

    return {
      status: 'success',
      action: {
        type: 'create',
        metadataName: 'myEntity',
        universalFlatEntity: universalFlatMyEntity,
      },
    };
  }

  protected buildUpdateAction(
    universalFlatMyEntity: UniversalFlatMyEntity,
    universalUpdates: Partial<UniversalFlatMyEntity>,
    flatEntityMaps: AllFlatEntityMapsByMetadataName,
  ): BuildWorkspaceMigrationActionReturnType<UniversalUpdateMyEntityAction> {
    const validationResult = this.flatMyEntityValidatorService.validateMyEntityForUpdate(
      universalFlatMyEntity,
      universalUpdates,
      flatEntityMaps.flatMyEntityMaps,
    );

    if (validationResult.length > 0) {
      return {
        status: 'failed',
        errors: validationResult,
      };
    }

    return {
      status: 'success',
      action: {
        type: 'update',
        metadataName: 'myEntity',
        universalFlatEntity: universalFlatMyEntity,
        universalUpdates,
      },
    };
  }

  protected buildDeleteAction(
    universalFlatMyEntity: UniversalFlatMyEntity,
  ): BuildWorkspaceMigrationActionReturnType<UniversalDeleteMyEntityAction> {
    const validationResult = this.flatMyEntityValidatorService.validateMyEntityForDelete(
      universalFlatMyEntity,
    );

    if (validationResult.length > 0) {
      return {
        status: 'failed',
        errors: validationResult,
      };
    }

    return {
      status: 'success',
      action: {
        type: 'delete',
        metadataName: 'myEntity',
        universalFlatEntity: universalFlatMyEntity,
      },
    };
  }
}

---

Step 3: Wire into Orchestrator (CRITICAL)

File: src/engine/workspace-manager/workspace-migration/workspace-migration-builder/workspace-migration-build-orchestrator.service.ts

@Injectable()
export class WorkspaceMigrationBuildOrchestratorService {
  constructor(
    // ... existing builders
    private readonly workspaceMigrationMyEntityActionsBuilderService: WorkspaceMigrationMyEntityActionsBuilderService,
  ) {}

  async buildWorkspaceMigration({
    allFlatEntityOperationByMetadataName,
    flatEntityMaps,
    isSystemBuild,
  }: BuildWorkspaceMigrationInput): Promise<BuildWorkspaceMigrationOutput> {
    // ... existing code

    // Add your entity builder
    const myEntityResult = await this.workspaceMigrationMyEntityActionsBuilderService.build({
      flatEntitiesToCreate: allFlatEntityOperationByMetadataName.myEntity?.flatEntityToCreate ?? [],
      flatEntitiesToUpdate: allFlatEntityOperationByMetadataName.myEntity?.flatEntityToUpdate ?? [],
      flatEntitiesToDelete: allFlatEntityOperationByMetadataName.myEntity?.flatEntityToDelete ?? [],
      flatEntityMaps,
      isSystemBuild,
    });

    // ... aggregate errors

    return {
      status: aggregatedErrors.length > 0 ? 'failed' : 'success',
      errors: aggregatedErrors,
      actions: [
        ...existingActions,
        ...myEntityResult.actions,
      ],
    };
  }
}

⚠️ This step is the most commonly forgotten! Your entity won't sync without orchestrator wiring.

---

Validation Patterns

Pattern 1: Required Field

if (!isDefined(field) || field.trim() === '') {
  errors.push({ code: ..., message: ..., userFriendlyMessage: ... });
}

Pattern 2: Uniqueness (O(1) lookup)

const existing = optimisticMaps.byName[entity.name];
if (isDefined(existing) && existing.id !== entity.id) {
  errors.push({ ... });
}

Pattern 3: Foreign Key Validation

if (isDefined(entity.parentId)) {
  const parent = parentMaps.byId[entity.parentId];
  if (!isDefined(parent)) {
    errors.push({ code: NOT_FOUND, ... });
  } else if (isDefined(parent.deletedAt)) {
    errors.push({ code: DELETED, ... });
  }
}

Pattern 4: Standard Entity Protection

if (entity.isCustom === false) {
  errors.push({ code: STANDARD_ENTITY_PROTECTED, ... });
  return errors; // Early return
}

---

Checklist

Before moving to Step 4:

• Validator service created
• Validator never throws (returns error arrays)
• Validator never mutates (uses optimistic maps)
• All uniqueness checks use indexed maps (O(1))
• Required field validation implemented
• Foreign key validation implemented
• Standard entity protection implemented
• Builder service extends WorkspaceEntityMigrationBuilderService
• Builder creates actions with universal entities
• Builder wired into orchestrator (CRITICAL)
• Builder injected in orchestrator constructor
• Builder called in buildWorkspaceMigration
• Actions added to orchestrator return statement

---

Next Step

Once builder and validation are complete, proceed to:
Syncable Entity: Runner & Actions (Step 4/6)

For complete workflow, see @creating-syncable-entity rule.