Module transform 

Pure CST→CST structural-edit transforms (E008 Phase 1a, ADR-0007).

This module gives ronin-core the named structural-edit vocabulary the E008 tree/form and table surfaces build on — insert / remove / reorder a struct field, map entry, or list/tuple element; set a value; rename a field/key; swap an enum variant; and add a field across every record of a list. Each op is a single, non-destructive apply_structural call that returns a fresh CstDocument sharing every untouched green subtree with the original (structural sharing), so every region the edit did not touch prints byte-for-byte identically (FR-013) and adjacent trivia on surviving siblings is preserved (FR-021).

Placement (ADR-0007)

These are the pure CST→CST transform functions of the split decided by ADR-0007: they live in ronin-core (reusable by a future LSP/web surface), navigate the document only through the typed crate::syntax::ast accessors, and compose over the existing non-destructive apply_edit primitive — they introduce no parallel edit engine. The selection→target resolution and the view/undo orchestration stay in ronin-app; selection, focus, view-state, and undo wiring MUST NOT enter this module.

WASM-clean (ADR-0007 / HINT-001 / project-instructions §II)

This module adds no filesystem / UI / async-runtime / native / time dependency. It uses only std and ronin-core’s own CST types + apply_edit, so the wasm32-unknown-unknown build of ronin-core stays green.

Addressing scheme

Each StructuralOp carries its target as an ast-navigable address: a parent collection node (ParentRef) plus, where a specific element is addressed, a child index into that parent’s elements (fields / entries / items, in source order). The caller (ronin-app, later) resolves a tree/table selection to one of these addresses; this module then re-resolves the address to a located CST node and composes the appropriate apply_edit call(s). Addressing by index into the located parent (rather than by a raw SyntaxNode handle) keeps a multi-step op (reorder, variant swap, add-field-across-rows) re-resolvable against each intermediate green tree the composition produces.

Outcome

Every op returns a TransformOutcome: TransformOutcome::Applied with the new document, or TransformOutcome::Blocked with a BlockedReason. A Blocked outcome leaves the input CST unchanged and produces no edit (a no-op never corrupts the document — project-instructions §I).

Enums

BlockedReason

Why a StructuralOp was TransformOutcome::Blocked.

ParentRef

Which collection a structural op targets, addressed by an ast-navigable reference (parent kind + index into the document).

StructuralOp

A single named structural-edit operation (the E008 transform vocabulary).

TransformOutcome

The result of applying a StructuralOp.

Functions

apply_structural

Apply one named structural StructuralOp to doc, returning a TransformOutcome.