Separate reflection projection handlers

docs/roadmap/implementation.md

@@ -1,6 +1,6 @@
 # Consolidation Implementation Plan
 
-Status: in progress. Stages 1 through 16 are complete; follow Stage 17 through Stage 20 in order.
+Status: in progress. Stages 1 through 17 are complete; follow Stage 18 through Stage 20 in order.
 The target executor is a Luna coding agent working through one end-to-end sprint.
 
 ## Authority, Baseline, And Execution
@@ -655,7 +655,7 @@ counter, budget checks, final expansion check, and one policy index remain intac
 Both mapping and identified-sequence adapters still use the shared executor.
 Validation group I passed.
 
-## Stage 17 — Extract Substantial Projection Handlers
+## Stage 17 — Extract Substantial Projection Handlers (Complete)
 
 **Owners:** engine `projection.go`, optionally new `projection_collection.go`.
 
@@ -678,6 +678,12 @@ Validation group I passed.
 original operation state. Do not refactor `clone`, `decodeValue`, or
 `valueBuilder.build` as an additional cleanup project.
 
+Progress notes (2026-10-25): delegated struct, map, and sequence projection to
+methods on the existing `valueOperation`. The dispatcher retains depth checks,
+pointer/dynamic handling, and scalar conversion; struct order, map sorting,
+flattened-node charging, nil slices, and cycle guards remain in their original
+paths. Validation group R passed.
+
 ## Stage 18 — Separate Schema Field Discovery And Assembly
 
 **Owner:** engine `schema.go`, optionally new `schema_fields.go`.

internal/engine/projection.go

@@ -39,89 +39,9 @@ func (o *valueOperation) project(value reflect.Value, descriptor *typeDescriptor
 
 	switch descriptor.kind {
 	case descriptorStruct:
-		result, issue := o.node(document.Mapping, path, depth)
+		return o.projectStruct(value, descriptor, path, depth)
-		if issue != nil {
-			return nil, issue
-		}
-		result.Mapping = make([]document.Entry, 0, len(descriptor.fields))
-		seen := make(map[string]bool, len(descriptor.fields))
-		for _, member := range descriptor.members {
-			memberValue := value.Field(member.index)
-			if member.inline {
-				if isNilValue(memberValue) {
-					continue
-				}
-				inline, issue := o.project(memberValue, member.descriptor, path, depth)
-				if issue != nil {
-					return nil, issue
-				}
-				if inline.Kind != document.Mapping {
-					return nil, &projectionIssue{code: CodeSchemaUnsupportedType, path: path.clone(), message: "inline value did not project to a mapping"}
-				}
-				o.nodes-- // The flattened container is not retained in the output tree.
-				for _, entry := range inline.Mapping {
-					if seen[entry.Key] {
-						return nil, &projectionIssue{code: CodeSchemaAmbiguousField, path: path.Key(entry.Key), message: "inline value conflicts with a declared field"}
-					}
-					seen[entry.Key] = true
-					result.Mapping = append(result.Mapping, entry)
-				}
-				continue
-			}
-			childPath := path.Key(member.name)
-			if seen[member.name] {
-				return nil, &projectionIssue{code: CodeSchemaAmbiguousField, path: childPath, message: "inline value conflicts with a declared field"}
-			}
-			if issue := o.charge(childPath); issue != nil { // mapping key
-				return nil, issue
-			}
-			child, issue := o.project(memberValue, member.descriptor, childPath, depth+1)
-			if issue != nil {
-				return nil, issue
-			}
-			seen[member.name] = true
-			result.Mapping = append(result.Mapping, document.Entry{Key: member.name, Value: child})
-		}
-		for _, entry := range result.Mapping {
-			field := descriptor.inlineMap
-			if index, ok := descriptor.fieldByName[entry.Key]; ok {
-				field = &descriptor.fields[index]
-			}
-			if field != nil && field.secret {
-				entry.Value.Sensitive = true
-			}
-		}
-		return result, nil
 	case descriptorMap:
-		if value.IsNil() {
+		return o.projectMap(value, descriptor, path, depth)
-			return o.node(document.Null, path, depth)
-		}
-		leave, issue := o.enter(value, path)
-		if issue != nil {
-			return nil, issue
-		}
-		defer leave()
-		result, issue := o.node(document.Mapping, path, depth)
-		if issue != nil {
-			return nil, issue
-		}
-		result.Mapping = make([]document.Entry, 0, value.Len())
-		keys := value.MapKeys()
-		slices.SortFunc(keys, func(left, right reflect.Value) int {
-			return cmp.Compare(left.String(), right.String())
-		})
-		for _, key := range keys {
-			childPath := path.Key(key.String())
-			if issue := o.charge(childPath); issue != nil {
-				return nil, issue
-			}
-			child, issue := o.project(value.MapIndex(key), descriptor.element, childPath, depth+1)
-			if issue != nil {
-				return nil, issue
-			}
-			result.Mapping = append(result.Mapping, document.Entry{Key: key.String(), Value: child})
-		}
-		return result, nil
 	case descriptorSlice:
 		if value.IsNil() {
 			return o.node(document.Null, path, depth)
@@ -131,22 +51,9 @@ func (o *valueOperation) project(value reflect.Value, descriptor *typeDescriptor
 			return nil, issue
 		}
 		defer leave()
-		fallthrough
+		return o.projectSequence(value, descriptor, path, depth)
 	case descriptorArray:
-		result, issue := o.node(document.Sequence, path, depth)
+		return o.projectSequence(value, descriptor, path, depth)
-		if issue != nil {
-			return nil, issue
-		}
-		result.Sequence = make([]*document.Node, 0, value.Len())
-		for i := 0; i < value.Len(); i++ {
-			childPath := path.Index(i)
-			child, issue := o.project(value.Index(i), descriptor.element, childPath, depth+1)
-			if issue != nil {
-				return nil, issue
-			}
-			result.Sequence = append(result.Sequence, child)
-		}
-		return result, nil
 	case descriptorDynamic:
 		if value.IsNil() {
 			return o.node(document.Null, path, depth)
@@ -217,6 +124,111 @@ func (o *valueOperation) project(value reflect.Value, descriptor *typeDescriptor
 	}
 }
 
+func (o *valueOperation) projectStruct(value reflect.Value, descriptor *typeDescriptor, path Path, depth int) (*document.Node, *projectionIssue) {
+	result, issue := o.node(document.Mapping, path, depth)
+	if issue != nil {
+		return nil, issue
+	}
+	result.Mapping = make([]document.Entry, 0, len(descriptor.fields))
+	seen := make(map[string]bool, len(descriptor.fields))
+	for _, member := range descriptor.members {
+		memberValue := value.Field(member.index)
+		if member.inline {
+			if isNilValue(memberValue) {
+				continue
+			}
+			inline, issue := o.project(memberValue, member.descriptor, path, depth)
+			if issue != nil {
+				return nil, issue
+			}
+			if inline.Kind != document.Mapping {
+				return nil, &projectionIssue{code: CodeSchemaUnsupportedType, path: path.clone(), message: "inline value did not project to a mapping"}
+			}
+			o.nodes-- // The flattened container is not retained in the output tree.
+			for _, entry := range inline.Mapping {
+				if seen[entry.Key] {
+					return nil, &projectionIssue{code: CodeSchemaAmbiguousField, path: path.Key(entry.Key), message: "inline value conflicts with a declared field"}
+				}
+				seen[entry.Key] = true
+				result.Mapping = append(result.Mapping, entry)
+			}
+			continue
+		}
+		childPath := path.Key(member.name)
+		if seen[member.name] {
+			return nil, &projectionIssue{code: CodeSchemaAmbiguousField, path: childPath, message: "inline value conflicts with a declared field"}
+		}
+		if issue := o.charge(childPath); issue != nil { // mapping key
+			return nil, issue
+		}
+		child, issue := o.project(memberValue, member.descriptor, childPath, depth+1)
+		if issue != nil {
+			return nil, issue
+		}
+		seen[member.name] = true
+		result.Mapping = append(result.Mapping, document.Entry{Key: member.name, Value: child})
+	}
+	for _, entry := range result.Mapping {
+		field := descriptor.inlineMap
+		if index, ok := descriptor.fieldByName[entry.Key]; ok {
+			field = &descriptor.fields[index]
+		}
+		if field != nil && field.secret {
+			entry.Value.Sensitive = true
+		}
+	}
+	return result, nil
+}
+
+func (o *valueOperation) projectMap(value reflect.Value, descriptor *typeDescriptor, path Path, depth int) (*document.Node, *projectionIssue) {
+	if value.IsNil() {
+		return o.node(document.Null, path, depth)
+	}
+	leave, issue := o.enter(value, path)
+	if issue != nil {
+		return nil, issue
+	}
+	defer leave()
+	result, issue := o.node(document.Mapping, path, depth)
+	if issue != nil {
+		return nil, issue
+	}
+	result.Mapping = make([]document.Entry, 0, value.Len())
+	keys := value.MapKeys()
+	slices.SortFunc(keys, func(left, right reflect.Value) int {
+		return cmp.Compare(left.String(), right.String())
+	})
+	for _, key := range keys {
+		childPath := path.Key(key.String())
+		if issue := o.charge(childPath); issue != nil {
+			return nil, issue
+		}
+		child, issue := o.project(value.MapIndex(key), descriptor.element, childPath, depth+1)
+		if issue != nil {
+			return nil, issue
+		}
+		result.Mapping = append(result.Mapping, document.Entry{Key: key.String(), Value: child})
+	}
+	return result, nil
+}
+
+func (o *valueOperation) projectSequence(value reflect.Value, descriptor *typeDescriptor, path Path, depth int) (*document.Node, *projectionIssue) {
+	result, issue := o.node(document.Sequence, path, depth)
+	if issue != nil {
+		return nil, issue
+	}
+	result.Sequence = make([]*document.Node, 0, value.Len())
+	for index := 0; index < value.Len(); index++ {
+		childPath := path.Index(index)
+		child, issue := o.project(value.Index(index), descriptor.element, childPath, depth+1)
+		if issue != nil {
+			return nil, issue
+		}
+		result.Sequence = append(result.Sequence, child)
+	}
+	return result, nil
+}
+
 func (o *valueOperation) node(kind document.Kind, path Path, depth int) (*document.Node, *projectionIssue) {
 	if issue := o.checkDepth(path, depth); issue != nil {
 		return nil, issue