Cache approved dynamic descriptors per operation

internal/engine/value_operation.go

@@ -24,21 +24,25 @@ type valueVisit struct {
 	length int
 }
 
-// valueOperation owns one traversal's cycle and budget state and reuses the
-// current load's descriptor cache for dynamic values.
+// valueOperation owns one traversal's cycle and budget state, and caches
+// dynamic descriptors approved for that traversal.
 type valueOperation struct {
-	cloneMode   secretCloneMode
-	schema      *schemaDescriptor
-	limits      projectionLimits
-	active      map[valueVisit]bool
-	nodes       int
-	nodeCredits int
+	cloneMode       secretCloneMode
+	schema          *schemaDescriptor
+	limits          projectionLimits
+	active          map[valueVisit]bool
+	approvedDynamic map[reflect.Type]*typeDescriptor
+	nodes           int
+	nodeCredits     int
 }
 
 func (o *valueOperation) dynamicDescriptor(current reflect.Type, path Path) (*typeDescriptor, *projectionIssue) {
 	if o.schema.secrets.Type != nil && current == o.schema.secrets.Type {
 		return nil, &projectionIssue{code: CodeSchemaDynamicType, path: path.clone(), message: "dynamic configuration values cannot establish secret-reference semantics"}
 	}
+	if descriptor, approved := o.approvedDynamic[current]; approved {
+		return descriptor, nil
+	}
 	builder := schemaBuilder{cache: o.schema.types, building: make(map[reflect.Type]bool), secrets: o.schema.secrets}
 	descriptor, issue := builder.describe(current, path)
 	if issue != nil {
@@ -49,6 +53,10 @@ func (o *valueOperation) dynamicDescriptor(current reflect.Type, path Path) (*ty
 		builder.rollback()
 		return nil, &projectionIssue{code: CodeSchemaDynamicType, path: path.clone(), message: "dynamic configuration values cannot establish secret-reference semantics"}
 	}
+	if o.approvedDynamic == nil {
+		o.approvedDynamic = make(map[reflect.Type]*typeDescriptor)
+	}
+	o.approvedDynamic[current] = descriptor
 	return descriptor, nil
 }