fix: better way of preventing unintended exports

sveltejs/svelte#12202 revealed that TypeScript has a harder time tracing imports when they are indirectly exposed, e.g. `function foo(): void; ... export { foo }` instead of `export function foo(): void;`, which can lead to bugs down the line. Ultimately this is a TypeScript limitation but in the meantime adding a lone `export {}` along `export function/const/etc` statements has the same effect as #82

CHANGELOG.md

@@ -1,5 +1,9 @@
 # dts-buddy changelog
 
+## 0.5.1
+
+- Use more TypeScript-friendly way of preventing unintended exports ([#85](https://github.com/Rich-Harris/dts-buddy/pull/85))
+
 ## 0.5.0
 
 - Prevent unintended exports ([#82](https://github.com/Rich-Harris/dts-buddy/pull/82))

src/create-module-declaration.js

@@ -398,24 +398,22 @@ export function create_module_declaration(id, entry, created, resolve) {
 			if (mod) content += '\n' + mod;
 		}
 
-		if (export_specifiers.length > 0) {
-			content += `\n\n\texport { ${export_specifiers.join(', ')} };`;
-		}
-
 		// finally, export any bindings that are exported from external modules
 
-		/** @type {string[]} */
-		const specifiers = [];
-
 		for (const name of exports) {
 			const declaration = trace_export(entry, name);
 			if (declaration?.external) {
-				specifiers.push(declaration.alias);
+				export_specifiers.push(declaration.alias);
 			}
 		}
 
-		if (specifiers.length > 0) {
-			content += `\n\texport { ${specifiers.join(', ')} };`;
+		// Always add an export { .. } statement, even if there are no exports. This ensures
+		// that only the public types are exposed to consumers of the declaration file. Due to some
+		// old TypeScript inconsistency, omitting the export statement would expose all types.
+		if (export_specifiers.length > 0) {
+			content += `\n\n\texport { ${export_specifiers.join(', ')} };`;
+		} else {
+			content += '\n\n\texport {};';
 		}
 
 		content += `\n}`;

test/samples/ambient-imports/output/index.d.ts

@@ -2,6 +2,8 @@
 
 declare module 'ambient-imports' {
 	export interface Foo {}
+
+	export {};
 }
 
 //# sourceMappingURL=index.d.ts.map

test/samples/basic/output 5.5/index.d.ts

@@ -1,6 +1,6 @@
 declare module 'basic' {
 	/** A vector with two components */
-	interface Vector2 {
+	export interface Vector2 {
 		/** The x component */
 		x: number;
 		/** The y component */
@@ -11,18 +11,18 @@ declare module 'basic' {
 	 * @param a the first vector
 	 * @param b the second vector
 	 * */
-	function add(a: Vector2, b: Vector2): Vector2;
+	export function add(a: Vector2, b: Vector2): Vector2;
 
-	export { Vector2, add };
+	export {};
 }
 
 declare module 'basic/subpackage' {
 	/**
 	 * Multiply two vectors
 	 * */
-	function multiply(a: import("basic").Vector2, b: import("basic").Vector2): import("basic").Vector2;
+	export function multiply(a: import("basic").Vector2, b: import("basic").Vector2): import("basic").Vector2;
 
-	export { multiply };
+	export {};
 }
 
-//# sourceMappingURL=index.d.ts.map
+//# sourceMappingURL=index.d.ts.map

test/samples/basic/output 5.5/index.d.ts.map

@@ -16,5 +16,5 @@
 		null,
 		null
 	],
-	"mappings": ";;WACiBA,OAAOA;;;;;;;;;;;UCKRC,GAAGA;;;;;;;;;UCAHC,QAAQA"
-}
+	"mappings": ";;kBACiBA,OAAOA;;;;;;;;;;;iBCKRC,GAAGA;;;;;;;;;iBCAHC,QAAQA"
+}

test/samples/const-namespace/output/index.d.ts

@@ -2,6 +2,8 @@ declare module 'const-namespace' {
 	export namespace a {
 		let x: number;
 	}
+
+	export {};
 }
 
-//# sourceMappingURL=index.d.ts.map
+//# sourceMappingURL=index.d.ts.map

test/samples/declare-module/output/index.d.ts

@@ -1,5 +1,7 @@
 declare module 'declare-module' {
 	export interface Foo {}
+
+	export {};
 }
 
 //# sourceMappingURL=index.d.ts.map

test/samples/deconflict-priority/output/index.d.ts

@@ -2,6 +2,8 @@ declare module 'deconflict-priority' {
 	export function x(foo: Foo, bar: Bar): void;
 	interface Foo {}
 	interface Bar {}
+
+	export {};
 }
 
 //# sourceMappingURL=index.d.ts.map

test/samples/enum/output/index.d.ts

@@ -4,6 +4,8 @@ declare module 'enum' {
 		VEGETABLE = 1,
 		MINERAL = 2
 	}
+
+	export {};
 }
 
-//# sourceMappingURL=index.d.ts.map
+//# sourceMappingURL=index.d.ts.map

test/samples/export-default-as/output/index.d.ts

@@ -3,6 +3,8 @@ declare module 'export-default-as' {
 	 * Add two numbers
 	 * */
 	export function add(a: number, b: number): number;
+
+	export {};
 }
 
 //# sourceMappingURL=index.d.ts.map

test/samples/export-default-function/output/index.d.ts

@@ -1,5 +1,7 @@
 declare module 'export-default-function' {
 	export default function foo(): void;
+
+	export {};
 }
 
 //# sourceMappingURL=index.d.ts.map

test/samples/export-default-value/output/index.d.ts

@@ -1,6 +1,8 @@
 declare module 'export-default-value' {
 	const _default: 42;
 	export default _default;
+
+	export {};
 }
 
 //# sourceMappingURL=index.d.ts.map

test/samples/export-from/output/index.d.ts

@@ -1,5 +1,7 @@
 declare module 'export-from' {
 	export const foo: "hello";
+
+	export {};
 }
 
 //# sourceMappingURL=index.d.ts.map

test/samples/export-named-as/output/index.d.ts

@@ -3,6 +3,8 @@ declare module 'export-named-as' {
 	 * Add two numbers
 	 * */
 	export function plus(a: number, b: number): number;
+
+	export {};
 }
 
 //# sourceMappingURL=index.d.ts.map

test/samples/export-type/output/index.d.ts

@@ -1,6 +1,8 @@
 declare module 'export-type' {
 	export type D = {};
 	export class B<D> {}
+
+	export {};
 }
 
-//# sourceMappingURL=index.d.ts.map
+//# sourceMappingURL=index.d.ts.map

test/samples/generics/output/index.d.ts

@@ -2,6 +2,8 @@ declare module 'generics' {
 	export interface Foo<T> {
 		bar: T;
 	}
+
+	export {};
 }
 
 //# sourceMappingURL=index.d.ts.map

test/samples/ignores-missing-sourcemap-segments/output/index.d.ts

@@ -3,6 +3,8 @@ declare module 'ignores-missing-sourcemap-segments' {
 	export namespace object {
 		let answer: number;
 	}
+
+	export {};
 }
 
-//# sourceMappingURL=index.d.ts.map
+//# sourceMappingURL=index.d.ts.map

test/samples/import-external-default/output/index.d.ts

@@ -1,6 +1,8 @@
 declare module 'import-external-default' {
 	import type { default as x } from 'external';
 	export function foo(input: x): x;
+
+	export {};
 }
 
-//# sourceMappingURL=index.d.ts.map
+//# sourceMappingURL=index.d.ts.map

test/samples/import-external-named-as-conflict/output/index.d.ts

@@ -1,7 +1,8 @@
 declare module 'import-external-named-as-conflict' {
 	import type { foo as f } from 'external';
 	export function foo(): void;
+
 	export { f };
 }
 
-//# sourceMappingURL=index.d.ts.map
+//# sourceMappingURL=index.d.ts.map

test/samples/import-external-named-as/output/index.d.ts

@@ -1,6 +1,7 @@
 declare module 'import-external-named-as' {
 	import type { foo as f } from 'external';
+
 	export { f };
 }
 
-//# sourceMappingURL=index.d.ts.map
+//# sourceMappingURL=index.d.ts.map

test/samples/import-external-named/output/index.d.ts

@@ -1,6 +1,7 @@
 declare module 'import-external-named' {
 	import type { foo } from 'external';
+
 	export { foo };
 }
 
-//# sourceMappingURL=index.d.ts.map
+//# sourceMappingURL=index.d.ts.map

test/samples/jsdoc-import/output 5.5/index.d.ts

@@ -4,7 +4,7 @@ declare module 'jsdoc-import' {
 	 * @param a the first vector
 	 * @param b the second vector
 	 * */
-	function add(a: Vector2, b: Vector2): Vector2;
+	export function add(a: Vector2, b: Vector2): Vector2;
 	/** A vector with two components */
 	interface Vector2 {
 		/** The x component */
@@ -13,7 +13,7 @@ declare module 'jsdoc-import' {
 		y: number;
 	}
 
-	export { add };
+	export {};
 }
 
-//# sourceMappingURL=index.d.ts.map
+//# sourceMappingURL=index.d.ts.map

test/samples/jsdoc-import/output 5.5/index.d.ts.map

@@ -13,5 +13,5 @@
 		null,
 		null
 	],
-	"mappings": ";;;;;;UAQgBA,GAAGA;;WCPFC,OAAOA"
-}
+	"mappings": ";;;;;;iBAQgBA,GAAGA;;WCPFC,OAAOA"
+}

test/samples/namespace-exports/output/index.d.ts

@@ -8,6 +8,8 @@ declare module 'namespace-exports' {
 			y: string;
 		}
 	}
+
+	export {};
 }
 
-//# sourceMappingURL=index.d.ts.map
+//# sourceMappingURL=index.d.ts.map

test/samples/overloads/output/index.d.ts

@@ -5,6 +5,8 @@ declare module 'overloads' {
 	}
 	export function baz(input: Foo): Foo;
 	export function baz(input: Bar): Bar;
+
+	export {};
 }
 
-//# sourceMappingURL=index.d.ts.map
+//# sourceMappingURL=index.d.ts.map

test/samples/path-config/output/index.d.ts

@@ -12,6 +12,8 @@ declare module 'path-config' {
 	type Input = number;
 	type Output = number;
 	export function foo_nested(input: Input): Output;
+
+	export {};
 }
 
 //# sourceMappingURL=index.d.ts.map

test/samples/preserve-comments/output/index.d.ts

@@ -3,6 +3,8 @@ declare module 'preserve-comments' {
 	 * @deprecated
 	 */
 	export function a(): number;
+
+	export {};
 }
 
 //# sourceMappingURL=index.d.ts.map

test/samples/preserved-jsdoc-tags/output/index.d.ts

@@ -6,6 +6,8 @@ declare module 'preserved-jsdoc-tags' {
 	 * const three = add(1, 2);
 	 * */
 	export function add(a: number, b: number): number;
+
+	export {};
 }
 
 //# sourceMappingURL=index.d.ts.map

test/samples/throws/output/index.d.ts

@@ -3,6 +3,8 @@ declare module 'throws' {
 	 * @throws {Error} nope
 	 * */
 	export function nope(): never;
+
+	export {};
 }
 
 //# sourceMappingURL=index.d.ts.map

test/samples/treeshaking-inline-import/output/index.d.ts

@@ -10,6 +10,8 @@ declare module 'treeshaking-inline-import' {
 		/** The y component */
 		y: number;
 	}
+
+	export {};
 }
 
 //# sourceMappingURL=index.d.ts.map

test/samples/ts/output/index.d.ts

@@ -15,6 +15,8 @@ declare module 'ts' {
 	 * Add two vectors
 	 */
 	export function add(a: Vector2, b: Vector2): Vector2;
+
+	export {};
 }
 
 declare module 'ts/subpackage' {
@@ -23,6 +25,8 @@ declare module 'ts/subpackage' {
 	 * Multiply two vectors
 	 */
 	export function multiply(a: Vector2, b: Vector2): Vector2;
+
+	export {};
 }
 
 //# sourceMappingURL=index.d.ts.map

test/samples/ts/output/index.d.ts.map

@@ -15,5 +15,5 @@
 		null,
 		null
 	],
-	"mappings": ";;kBACiBA,OAAOA;;;;;;;kBAQPC,OAAOA;;;;;;;iBAQRC,GAAGA;;;;;;;;iBCZHC,QAAQA"
+	"mappings": ";;kBACiBA,OAAOA;;;;;;;kBAQPC,OAAOA;;;;;;;iBAQRC,GAAGA;;;;;;;;;;iBCZHC,QAAQA"
 }