Property constraint

To add a new constraint (let's say represented by foo_contraint) it is expected that:

• The foo_contraint property is registered with the validation schema (property-constraint-schema.v1.json) hereby defines its characteristics (array, boolean, pattern etc.)
• A new class is added that implements the Constraint interface and interprets the foo_contraint property together with the constraint boundaries
• The foo_contraint property and the newly created class are registered with the ConstraintRegistry
• The newly created Constraint class is added to the ConstraintFactory to define the object graph

When adding new constraints, please ensure that:

• Unit tests carefully test the expected behaviour
• The ConstraintRegistryTest and ConstraintFactoryTest are extended

TYPE_DEFERRED

When a constraint is expected to be expensive (in terms of performance, runtime) it should be postponed and be derived from the DeferrableConstraint class to ensure that those checks are run using the DeferredConstraintCheckUpdateJob hereby avoiding unnecessary resource hogging during a page view/GET process.

See also

• How to register a https://github.com/SemanticMediaWiki/SemanticMediaWiki/blob/master/docs/examples/register.custom.constraint.md "custom constraint"