[Indra-db]

Upgrade flecs core to upstream master 6e4cd338a

Flecs core: Upgrades base from 9930c85 to upstream master 6e4cd338a (474 upstream commits).
Vendored via: Fork integration branch 8a7c39fab (merges indradb/on-replace, table_column_locks_cr_locks, indradb/rust).

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User-Facing Additions

Hierarchy & Entities

• Two hierarchy storage models, named after the mechanism they use:
  • world.entity_child_of(parent) / entity_named_child_of() / prefab_child_of() / prefab_named_child_of() — fragmenting (ChildOf, parent) pair storage. Each distinct parent is a distinct pair id, so children of different parents live in different tables: fast per-parent iteration, full cascade/up query support, but many parents means many tables and reparenting is an archetype move. Same mechanism as the .child_of() builder method.
  • world.entity_with_parent(parent) / entity_named_with_parent() — non-fragmenting hierarchy via the new flecs::Parent component (plus (ParentDepth, depth) value pair). The parent is column data, so all children share tables regardless of parent: no table explosion with thousands of parents, and reparenting is a cheap component write instead of an archetype move. Built for deep or highly dynamic scene graphs.
  • Rule of thumb: few parents / heavy cascade-style queries → child_of; huge parent counts / frequent reparenting → with_parent.
• Builtins: Added flecs::Parent, flecs::TreeSpawner, and flecs::ParentDepth.
• World APIs: Added World::each_alive_entity(), World::new_mini(), World::release(), is_defer_suspended(), and the entity range API (entity_range_new/set/get, EntityRange).
• Entity Pair Support: set_ptr/set_ptr_with_size now accept pairs (impl IntoId, upstream #1866); modules get (With, Singleton).

Queries & Optimization

• SparseQuery (world.sparse_query::<T>()): Cache-less, allocation-free iteration directly over sparse component storages. Component requirements checked at compile time.
• Compile-Time Traits: #[flecs(traits(Sparse))], traits(DontFragment), and traits((OnInstantiate, ...)) now emit ComponentInfo consts (IS_SPARSE, IS_DONT_FRAGMENT, ON_INSTANTIATE). Invalid sparse-query combinations fail at compile time.
• Sparse Get Fast Path: get/try_get/cloned on compile-time sparse/dont_fragment components bypass table-record lookups and read directly from sparse storage. (Parity with C++ is_get_sparse_component; non-pair components only).
• Query Grouping: group_by is now unsorted by default. Added .group_by_ordered(), group flags, Query::each_group(), System::set_group()/clear_group(), and Query::has()/has_table()/has_table_range().

Systems, Observers & Hooks

• Re-configuration: Added Observer::update::<T>() and System::update::<T>(). Builders now create entities lazily; system phase is set via desc.phase.
• Component::on_validate(): Runs before on_set/OnSet. Returning false suppresses them.
• Component::on_replace(): (entity, prev, next) callback invoked before next overwrites prev.

⚠️ Rust Semantics Difference: Unlike C/C++, this hook only fires if the component already existed (preventing &mut T on unconstructed memory). First-time sets or deferred batch sets do not fire it. Registering this hook disallows mutable-pointer operations (get_mut, ensure, emplace).

Meta & Examples

• Reflection & Meta: Added UntypedComponent::create_member_entities() (required for member DSL queries/metrics/alerts), flecs::meta::Map/Value types, EcsTypeKind variants, and member accessors.
• Examples: Added 8 new examples covering traits, hierarchy, validation, and reflection.

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API Renames (rust-idiomatic naming)

• _w_ → _with_ throughout the Rust API (the _w_ abbreviation stays C-only): set_ptr_with_size, path_with_sep, path_from_with_sep, set_rate_with_tick_source, entity_bulk_with_entity_ids, EntityView::new_with_parent/new_with_id/new_with_entity/new_with_entity_ids. FFI symbols (sys::ecs_field_w_size, etc.) are unchanged, they mirror C.

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Breaking Changes

• Hierarchy: Removed EntityView::child() and child_named(). Use world.entity_child_of(parent) or entity_named_child_of(parent, name) instead.
• Module reparenting: now destructs the old parent scope unconditionally (upstream 4fd6b8dca parity). Entities left in a namespace a module is reparented out of are deleted with it — don't share a module's pre-reparent namespace with your own entities.
• Internals: Removed flecs::Private/FlecsInternals. Builtin ID renumbering updated to match upstream.
• Meta: Flecs no longer creates member entities automatically on struct registration. Call create_member_entities() per type if needed.
• Ordering: group_by iteration order is now unspecified unless group_by_ordered is explicitly used.
• Traits & Hooks:
  • Dynamically adding (OnInstantiate, Inherit) to a compile-time sparse component now asserts in debug builds. Use #[flecs(traits(...))] instead.
  • on_replace only fires on genuine replacement. Ported C/C++ code relying on it for first-time initialization must migrate to on_add/on_set.

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Soundness & Bug Fixes

• Fixed UB in CachedRef (Release Builds): Fixed a bug where CachedRef read uninitialized memory in release profiles because bindings lacked the FLECS_DEBUG trailing fields. Bindings are now profile-matched, and CachedRef stores the component ID directly.
• Locks-off builds compile again: Without flecs_safety_locks, ecs_get_ptr_t is a bare void*; field accesses now go through get_ptr_raw()/get_ptr_null() helpers (Rust mirror of C's ECS_GET_PTR_PTR/ECS_GET_PTR_NULL), fixing every feature-subset combination in cargo hack --each-feature.
• Iterator Contract Rework: Field resolution now defaults to the it.columns primary path with it.trs null-guarded. This fixes multiple null-dereference aborts (hooks, sparse terms, enum systems) that previously caused infinite panic loops.
• Hardened field::<T> Validation: Pair terms now verify that ecs_get_typeid(term_id) matches T in release builds to prevent type reinterpretation mismatches.
• Typed-Pair Wildcards: get now resolves the concrete ID via ecs_search before casting; null-table guarded.

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Tooling & Infrastructure

• Profile-Matched Bindings: bindgen now runs twice per regeneration to generate distinct bindings.rs (FLECS_DEBUG) and bindings_release.rs (FLECS_NDEBUG) modules, automatically selected by Cargo's build profile.
• ABI Drift Guard: Added abi_test using ecs_rust_sizeof_* shims to assert that Rust size_of perfectly matches C sizeof across both profiles.
• Regeneration hardening: regenerate_binding removed from flecs_ecs_sys default features (standalone sys builds no longer silently clobber committed bindings); regen via cargo make regenerate-bindings (full addon feature set); new CI bindings-check job regenerates and fails on drift.
• Test Suite: Ported new upstream C++ tests across all major sub-systems (41 new tests, including dynamic-inherit abort tests, debug-gated since ecs_check compiles out under NDEBUG). Integrated rstest templates for fragment/sparse/dont_fragment component lifecycles.