[apotema]

Closes #886.

Problem

src/script_contract.zig built its set of scene built-ins from a hand-written list (Sprite, Shape, Tilemap, Camera, Image). It left out Emitter, so labelle_component_set("Emitter", …) fell through to the registry loop and returned -1, even though scenes, .zon and prefab refresh all accept it. This was the third site that listed built-ins by hand. #884 fixed the other two.

Fix

• builtin_comps is now derived from scene.builtins.Builtin. It keeps the enum's shadowable rule: Sprite/Shape are always built-ins, and Tilemap/Camera/Image/Emitter step aside when the project registers a component with the same name. Each type comes from Builtin.Type(G).

• The code that differs per built-in is now written as exhaustive switches over Builtin:

  • setBuiltinComponent (which apply fn to call)
  • builtinJsonInto (get serialization and the batch write-back)
  • the typed teardown in componentRemoveImpl

  The old if (eql(name, "Sprite")) … else chains are gone, so adding a tag to Builtin without handling it here is a compile error.

• Emitter:

  • set goes through the scene's own applyEmitter, which also turns on drive_particles.
  • After that it calls refreshParticleSystem, so a live pool picks up the new config.
  • remove drops the component and frees the pool right away, even while the game is hard-paused.

• contract/labelle_script.h support table and the module docs now list Emitter. This is an additive change, so there is no version bump.

Tests

New file test/script_contract_builtins_test.zig, added to build.zig:

• Drift guard: loops over scene.builtins.names. For each built-in it checks that set/get/has/remove work from a script and that the stored component is the engine's built-in type.
• Emitter set/get: checks drive_particles gets turned on (only applyEmitter does that), a get→set round-trip, the preset enum, and that malformed JSON returns -1 and leaves the entity untouched.
• Emitter resync: after a tick, a re-set drops the stale ParticleSystem at set time, and the next tick rebuilds it with the new rate. A remove under setTimeScale(0) frees it immediately.
• Shadowing: when a project registers its own Emitter, set/get/remove go to the registry type, the engine type never appears, and drive_particles stays off.

How the tests were checked locally (Windows, Zig 0.16.0, zig build test):

• Fake enum tag: added a fake tag Fake886 to Builtin. With no Fake886Comp decl, the derivation fails to compile (a clear @compileError), and so does entity_writer's switch. After adding Fake886Comp on Game, all three script_contract switches failed: switch must handle all possibilities at lines 1564 (set), 1589 (get JSON) and 1769 (remove).
• Old bug: skipped .Emitter in the derivation to reproduce it. The drift-guard test and both Emitter tests failed.
• Probe: a temporary probe error made the new test file fail, which confirms the file really runs.
• Clean run: the final run has the same failure count as origin/main on this Windows machine (47 failed + 7 crashed on both, from tests that already fail on Windows: sockets and u64 pid types). None of those failures are in the script contract tests.

🤖 Generated with Claude Code

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📥 Commits

Reviewing files that changed from the base of the PR and between 1f238a7 and f5993ea.

📒 Files selected for processing (4)

• build.zig
• contract/labelle_script.h
• src/script_contract.zig
• test/script_contract_builtins_test.zig

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Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-09-28T23:49:29.127796Z	f5993ea	PR opened

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