figma.combineAsVariants() was unimplemented in the scripting/automation
layer (figma-api/proxy.ts's compatibility surface), even though the editor
UI already has a full equivalent — createComponentSetFromComponents()
(editor/components.ts) plus wrapSelectionInContainer()
(editor/structure/container-wrap.ts) — wired to the app's own "Create
component set" menu action.
This ports that logic down to FigmaAPI (the class MCP tools, the CLI, and
AI chat scripting all run against): wraps selected COMPONENT nodes sharing
a parent into a COMPONENT_SET, and derives variant property definitions from
"Category/Value" node-name segments, matching the editor behavior exactly.
Drops the undo-stack push and selection-state writes the editor path has,
since neither concept exists at the scripting layer — everything else is
the same primitives (SceneGraph.createNode/insertChildAt/reparentNode),
which FigmaAPI already had direct access to.
Also adds a matching combine_as_variants tool (packages/core/src/tools/
create/components.ts) registered in EXTENDED_TOOLS, so it's exposed
through MCP, the CLI, and AI chat alongside the existing create_component/
create_instance tools.
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