feat: allow making class properties private

packages/@cdklabs/typewriter/src/interface.ts

@@ -1,5 +1,5 @@
 import { MemberType } from './member-type';
-import { PropertySpec } from './property';
+import { Property, PropertySpec } from './property';
 import { IScope } from './scope';
 import { Type } from './type';
 import { DeclarationKind, TypeSpec } from './type-declaration';
@@ -44,4 +44,13 @@ export class InterfaceType extends MemberType {
   public update<A extends Omit<Partial<InterfaceSpec>, 'properties' | 'methods' | 'name'>>(updates: A) {
     Object.assign(this.spec, updates);
   }
+
+  /**
+   * Adds a property to the interface
+   *
+   * Interface properties must be public.
+   */
+  public addProperty(spec: Omit<PropertySpec, 'protected' | 'visibility'>): Property {
+    return super.addProperty(spec);
+  }
 }

packages/@cdklabs/typewriter/src/member-type.ts

@@ -29,6 +29,10 @@ export abstract class MemberType extends TypeDeclaration {
    * Adds a property to the interface
    */
   public addProperty(spec: PropertySpec): Property {
+    if (spec.protected && spec.visibility) {
+      throw new Error('Cannot specify both "protected" and "visibility"');
+    }
+
     const prop = new Property(this, {
       ...spec,
     });

packages/@cdklabs/typewriter/src/property.ts

@@ -21,9 +21,20 @@ export interface PropertySpec {
   /**
    * Indicates if this property is protected (otherwise it is public)
    *
+   * @deprecated Use visibility instead.
    * @default false
    */
   protected?: boolean;
+
+  /**
+   * Indicates the visibility of this property
+   *
+   * Cannot be used together with `protected`.
+   *
+   * @default false
+   */
+  visibility?: MemberVisibility;
+
   /**
    * Indicates if this property is abstract
    *
@@ -106,6 +117,9 @@ export class Property extends TypeMember implements IProperty {
    * The visibility of the member.
    */
   public get visibility(): MemberVisibility {
+    if (this.spec?.visibility !== undefined) {
+      return this.spec.visibility;
+    }
     if (this.spec?.protected) {
       return MemberVisibility.Protected;
     }

packages/@cdklabs/typewriter/src/struct.ts

@@ -38,8 +38,10 @@ export class StructType extends MemberType {
 
   /**
    * Adds a property to the interface
+   *
+   * Struct members are always public and immutable.
    */
-  public addProperty(spec: Omit<PropertySpec, 'immutable'>): Property {
+  public addProperty(spec: Omit<PropertySpec, 'immutable' | 'protected' | 'visibility'>): Property {
     return super.addProperty({
       ...spec,
       immutable: true,

packages/@cdklabs/typewriter/test/class.test.ts

@@ -1,4 +1,4 @@
-import { Block, ClassType, MemberVisibility, Module, TypeScriptRenderer } from '../src';
+import { Block, ClassType, expr, MemberVisibility, Module, Type, TypeScriptRenderer } from '../src';
 
 const renderer = new TypeScriptRenderer();
 let scope: Module;
@@ -26,6 +26,25 @@ test('class with a private constructor', () => {
   `);
 });
 
+test('class with a private property', () => {
+  const c = new ClassType(scope, {
+    name: 'MyClass',
+  });
+  c.addProperty({
+    name: 'myProperty',
+    type: Type.STRING,
+    visibility: MemberVisibility.Private,
+    initializer: expr.lit('Hello World'),
+  });
+
+  expect(renderer.render(scope)).toMatchInlineSnapshot(`
+    "/* eslint-disable prettier/prettier, @stylistic/max-len */
+    class MyClass {
+      private myProperty: string = "Hello World";
+    }"
+  `);
+});
+
 test('can update some class spec fields after initial creation', () => {
   const c = new ClassType(scope, {
     name: 'MyClass',