Third version of our transform, which creates the new AST nodes for the getter and setter

transform-value.v3.ts

// Dependencies:
// ...
import { tstemplate } from '@phenomnomnominal/tstemplate';

// Constants:
// ...
const RESULT_QUERY = 'PropertyDeclaration, GetAccessor, SetAccessor';

const GETTER_SETTER_TEMPLATE = tstemplate.compile(`
    class Template {
        private <%= privateName %>: <%= type %>;
        public get <%= name %> ():  <%= type %> {
            let val = this.<%= privateName %>
            return val;
        }
        public set <%= name %> (value: <%= type %>) {
            let val = value;
            this.<%= privateName %> = val;
        }
    }
`);

export function transformer (source: SourceFile): TransformerFactory<Node> {
    // ...
}

export function valueDecoratorToGetterAndSetterFactory (nodes: Array<Node>): TransformerFactory<Node> {
    return function (context: TransformationContext): Transformer<Node> {
        // ...
        function visit (node: Node): Node | Array<Node> {
            if (nodes.includes(node)) {
                // Create the base structure of the new getter/setter:
                const property = node as PropertyDeclaration;
                const propertyName = property.name.getText();
                const [internal, getter, setter] = tsquery(GETTER_SETTER_TEMPLATE({
                    name: property.name,
                    privateName: createIdentifier(`_${propertyName}`),
                    type: property.type! || createToken(SyntaxKind.AnyKeyword)
                }), RESULT_QUERY);

                // Return the new AST nodes to replace the old one:
                return [internal, getter, setter];
            }
        }
    };
}