Add query filters

[waynemwashuma]

Objective

Introduces query filters to enhance the ECS query capabilities. Query filters add powerful new ways to filter entities arbitrarily e.g based on component presence or absence.

The query system has been enhanced with the following:

• QueryFilter: The interface which provides a base for other filters to be implemented on.
• Has filter: Includes entities that have the specified component
• Without filter: Exclude entities that have the specified component

The filters are composable i.e multiple filters can be combined in a single query.
More filters can be added in the future as this change provides the base for more filters.

Note

The filters work at the archetype level for now but can be adapted to per entity filtering.

Showcase

Using query filters is straightforward:

// Query entities of which we will read/modify `ComponentA` but it should have `ComponentB` and without `ComponentC`.
const query = new Query(world, [ComponentA], [has(ComponentB), without(ComponentC)])

// Count matching entities
const count = query.count()

// Iterate through filtered results
query.each(([componentA]) => {
  // Process filtered entities
})

Migration Guide

Existing queries continue to work unchanged. To use filters, add them as the third parameter to Query constructor.

Checklist

• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.