🐛 Do not generate an empty declaration file

src/fixtures/no-declaration-file.css

@@ -0,0 +1,9 @@
+html {
+    box-sizing: border-box;
+}
+
+*,
+*:before,
+*:after {
+    box-sizing: inherit;
+}

src/logic.js

@@ -6,9 +6,18 @@ import { parse as parseCss, walk } from "css-tree";
 
 /* globals process -- Node/CLI tool */
 
+/**
+ * Generates TypeScript declaration file for the stylesheet file at the given
+ * `path`. Includes the given `time` in the generated comment.
+ *
+ * @param path {string} - Path to stylesheet file.
+ * @param time {string} - Timestamp string to include in generated comment.
+ * @returns {Promise<string | undefined>} TypeScript declaration file content or
+ *   `undefined` if no declarations to write.
+ */
 export async function generateDeclaration(path, time) {
 	// Handle case where the file got deleted by the time we got here
-	if (!existsSync(path)) return;
+	if (!existsSync(path)) return undefined;
 
 	const css = await readFile(path, `utf8`);
 
@@ -28,7 +37,8 @@ export async function generateDeclaration(path, time) {
 		}
 	});
 
-	return ts;
+	// Only return TypeScript if we wrote something
+	return exportedNames.size === 0 ? undefined : ts;
 }
 
 export function dtsPath(path) {

src/logic.test.js

@@ -9,11 +9,20 @@ import { dtsPath, generateDeclaration } from "./logic.js";
 const __dirname = dirname(fileURLToPath(import.meta.url));
 
 describe(`css-typed`, () => {
+	it(`should not generate an empty declaration file [#9]`, async () => {
+		const path = fixtureFile(`no-declaration-file.css`);
+		expect(await generateDeclaration(path, `$TIME`)).toBeUndefined();
+	});
+
 	describe.each([`foo.css`, `foo.module.css`])(`%s`, (filename) => {
 		it(`should match expected output`, async () => {
-			const path = join(__dirname, `fixtures`, filename);
+			const path = fixtureFile(filename);
 			const expected = readFileSync(dtsPath(path), { encoding: `utf8` });
 			expect(await generateDeclaration(path, `$TIME`)).toStrictEqual(expected);
 		});
 	});
 });
+
+function fixtureFile(filename) {
+	return join(__dirname, `fixtures`, filename);
+}

src/main.js

@@ -35,7 +35,15 @@ async function main(pattern) {
 	process.exit(0);
 }
 
+/**
+ * Writes the TypeScript declaration content to file. Handles the output path.
+ *
+ * @param path {string} - Path to the original stylesheet file. NOT the path to write.
+ * @param ts {string | undefined} - The TypeScript declaration content to write.
+ * @returns {Promise<undefined>} Empty promise indicating when writing has completed.
+ */
 async function writeDeclarationFile(path, ts) {
+	if (!ts) return undefined;
 	await writeFile(dtsPath(path), ts, `utf8`);
 	return undefined;
 }