feat: allow free function exports in typewriter

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

@@ -6,7 +6,7 @@ import { Statement } from './statements';
 import { Block } from './statements/block';
 import { asStmt } from './statements/private';
 import { Type } from './type';
-import { DeclarationKind, TypeDeclaration, TypeSpec } from './type-declaration';
+import { DeclarationKind, Exportable, TypeDeclaration, TypeSpec } from './type-declaration';
 
 export interface CallableSpec extends TypeSpec {
   name: string;
@@ -29,7 +29,7 @@ export interface CallableExpr {
 /**
  * Can't be called "Function"
  */
-export class FreeFunction extends TypeDeclaration implements CallableDeclaration {
+export class FreeFunction extends TypeDeclaration implements CallableDeclaration, Exportable {
   public readonly returnType: Type;
   public readonly kind = DeclarationKind.Function;
   public readonly parameters = new Array<Parameter>();

packages/@cdklabs/typewriter/src/renderer/typescript.ts

@@ -55,7 +55,7 @@ import {
 import { StructType } from '../struct';
 import { ThingSymbol } from '../symbol';
 import { PrimitiveType, Type } from '../type';
-import { TypeParameterSpec } from '../type-declaration';
+import { Exportable, TypeParameterSpec } from '../type-declaration';
 import { Initializer, MemberVisibility, Method } from '../type-member';
 
 /**
@@ -431,11 +431,10 @@ export class TypeScriptRenderer extends Renderer {
     throw new Error(`Symbol ${sym} (in ${sym.scope}) not visible from ${this.scopes[0]} (missing import?)`);
   }
 
-  protected renderFunction(func: CallableDeclaration) {
+  protected renderFunction(func: CallableDeclaration & Exportable) {
     this.renderDocs(func);
     this.emit(`// @ts-ignore TS6133\n`);
-
-    this.emit(`function ${func.name}`);
+    this.emit(`${func.export ? 'export ' : ''}function ${func.name}`);
     this.renderParameters(func.parameters);
     if (func.returnType) {
       this.emit(': ');

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

@@ -52,7 +52,7 @@ export interface TypeSpec extends Documented, Exportable {
 /**
  * An abstract jsii type
  */
-export abstract class TypeDeclaration implements Documented {
+export abstract class TypeDeclaration implements Documented, Exportable {
   /**
    * The simple name of the type (MyClass).
    */
@@ -83,6 +83,13 @@ export abstract class TypeDeclaration implements Documented {
     return !!this.spec.export;
   }
 
+  /**
+   * Whether this type is being exported from its scope
+   */
+  public get export() {
+    return !!this.spec.export;
+  }
+
   /**
    * The generic type parameters of the type
    */

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

@@ -0,0 +1,48 @@
+import { FreeFunction, Module, TypeScriptRenderer } from '../src';
+
+const renderer = new TypeScriptRenderer();
+let scope: Module;
+
+beforeEach(() => {
+  scope = new Module('typewriter.test');
+});
+
+describe('functions', () => {
+  test('functions are implicitly not exported', () => {
+    new FreeFunction(scope, {
+      name: 'freeFunction',
+    });
+
+    expect(renderer.render(scope)).toMatchInlineSnapshot(`
+      "/* eslint-disable prettier/prettier, max-len */
+      // @ts-ignore TS6133
+      function freeFunction(): void;"
+    `);
+  });
+
+  test('functions can be explicitly exported', () => {
+    new FreeFunction(scope, {
+      name: 'freeFunction',
+      export: true,
+    });
+
+    expect(renderer.render(scope)).toMatchInlineSnapshot(`
+      "/* eslint-disable prettier/prettier, max-len */
+      // @ts-ignore TS6133
+      export function freeFunction(): void;"
+    `);
+  });
+
+  test('functions can be explicitly not exported', () => {
+    new FreeFunction(scope, {
+      name: 'freeFunction',
+      export: false,
+    });
+
+    expect(renderer.render(scope)).toMatchInlineSnapshot(`
+      "/* eslint-disable prettier/prettier, max-len */
+      // @ts-ignore TS6133
+      function freeFunction(): void;"
+    `);
+  });
+});