component-pipeline

name	component-pipeline
description	The production line for wrapping one Slate widget end-to-end — research the real header, fill the adapter from the template, style keys, contract case, test, docs. The repetitive lesser-model workload; one run = one widget. Use when adding any RUI::* widget wrapper (Phase 2 batch 1, Phase 7 batch 2, and beyond).

Component pipeline — one Slate widget, six stations

Exit gate for a run: build green + Automation RunTests ReactiveUI.Widgets.<Name> green + ReactiveUI.Contract green + docs-sync done. Model tiers (MASTER_PLAN §8): station 1 is sonnet-class (judgment about the widget's API); stations 2–6 are haiku-class once the prop-map entry exists. Anything requiring a NEW host-config mechanism (a new slot model, an item-view adapter) is NOT this pipeline — STOP and escalate to an opus-class session.

Stations

1. Research the real widget. Read the actual header — Engine/Source/Runtime/Slate/Public/Widgets/**/S<Name>.h (or SlateCore) — plus its style struct (F<Name>Style in Styling/SlateTypes.h). Enumerate every SLATE_ARGUMENT, SLATE_ATTRIBUTE, SLATE_EVENT, SLATE_SLOT_ARGUMENT, and post-construction setter. The header outranks the docs — Epic's web docs lag. Write the findings into the widget's entry in the prop-map schema (templates/prop-map.schema.json documents the shape) — the single source the adapter, the LSP vocabulary, and the docs all consume.
2. Wrapper. Instantiate templates/widget_wrapper.template.cpp: props struct (RUI_PROP rows), builder methods, adapter (Create with construct-only args → ApplyFull; ApplyDiff setter rows; Equals; child-container kind; reconstruct-on mask; event table rows).
3. Style keys. Add each styleable property to the central style-key registry with type, default, setter, and reset behavior. Hot-path keys (colors/opacity/font/padding) must NOT be on the reconstruct mask (MASTER_PLAN D-13).
4. Contract case. Add the widget's apply/remove/reset case to the contract corpus: props applied → widget state asserted; style prop removed → default restored; plain prop removed → NOT reset (the family semantic).
5. Test. Instantiate templates/widget_test.template.cpp → IMPLEMENT_SIMPLE_AUTOMATION_TEST(FRui<Name>Test, "ReactiveUI.Widgets.<Name>", …). Demonstrate it red→green once (break the adapter, watch it fail, restore).
6. Docs. Run the docs-sync skill (new-widget row).

Known traps (read BEFORE station 1)

• SLATE_ARGUMENT vs SLATE_ATTRIBUTE: attributes are TAttribute<T> and usually have runtime setters; arguments are construct-only → they go on the reconstruct mask (changing one replaces the widget: focus/caret/scroll loss — document per widget).
• We pass constant attribute values and mutate via setters — never bind delegate TAttributes (D-12; polling kills the fast path).
• Slot props live on the SLOT, not the widget (padding/alignment/fill/ZOrder) — they belong in the child's slot.* namespace, applied via the parent adapter's slot setters.
• Events return FReply on many widgets: the proxy returns Handled() for void user callbacks; expose the FReply-returning overload only where pass-through matters (D-27/Phase 2 decision).
• Editable-text widgets: skip the setter when the value is equal (caret preservation) — the generalized self-notifying-setter guard (D-16).
• Not every FArguments arg has a setter — verify against the header, not hope; a missing setter means reconstruct-mask, not a silent no-op.
• Stateful widgets (editable text, list views) are excluded from the widget pool.

Scar tissue (why these steps exist)

• "Header outranks docs": a docs-sourced prop list once included an attribute the shipping header had removed — the header is ground truth, the sweep verifies against it.
• The prop-map entry comes FIRST (station 1 output): wrappers written before the schema entry drifted from the LSP vocabulary — one source, everything generated from it.
• Red→green once is mandatory: a widget test that never failed was later found to be asserting nothing.
• The reconstruct mask is per-widget documented, because "why did my style tweak eat my focus" is the exact bug class D-13 exists to prevent — keep hot-path styling off the mask.