Validation and debugging

Validation placement

Use both layers when appropriate:

• Override IsDataValid on the definition class for invariants that belong to that object.
• Derive UEditorValidatorBase to validate assets across engine/custom classes or enforce project-wide policy. Implement CanValidateAsset and ensure every ValidateLoadedAsset path calls AssetPasses or AssetFails.

Validate through Content Browser actions, Tools > Validate Data, and CI:

UnrealEditor-Cmd.exe Project.uproject -run=DataValidation

The commandlet runs C++ rules by default. Blueprint/Python validation support requires explicit extension; Python validators must register with UEditorValidatorSubsystem.

Definition checks

At minimum validate:

• ID is present, unique, governed, and consistent with the asset/row when required;
• numeric values are finite and within domain ranges;
• required hard/soft references resolve and have allowed classes;
• mutually exclusive options are not both selected;
• dependent fields are present together;
• rows/reference targets exist;
• no forbidden dependency cycle or editor-only content crosses into runtime;
• Asset Manager ID and bundle/cook expectations are satisfied.

Use errors for content that cannot ship and warnings for suspicious but valid states. Include asset path, field, received value, expected rule, and a repair action in every message.

Failure routing

Symptom	Check first
Primary Asset ID not found	Actual ID, type config, base-class mode, scan path, excluded path
Soft pointer is null	Was it loaded, did load finish, did the path redirect, is target cooked?
Table lookup fails	Correct table, exact row key, schema/import warnings, reimport result
Values do not update	Cached row pointer/copy, stale reimport, wrong source authority
Unexpected memory spike	Hard reference chain, broad bundle, synchronous load, retained handle
Works in PIE, fails packaged	Cook rule, Primary Asset Label, editor-only class/path, chunk availability
Registry query misses assets	Initial scan incomplete, wrong class path/filter, asset not resaved for tags

Log stable IDs and package paths at load boundaries. Do not “fix” missing data by silently substituting unrelated content unless the product explicitly defines that fallback.