fix: keep the Content-Disposition filename ASCII for non-ASCII file names

src/index.js

@@ -219,7 +219,11 @@ const getHeaders = async (handlers, config, current, absolutePath, stats) => {
 			// if that's not working, it will save the file. But to be clear: This
 			// only happens if it cannot find a appropiate value.
 			'Content-Disposition': contentDisposition(base, {
-				type: 'inline'
+				type: 'inline',
+				// Node.js rejects non-ASCII header values on some responses, so
+				// the plain `filename` parameter must stay ASCII. The full name
+				// goes into `filename*`.
+				fallback: base.replace(/[^\x20-\x7e]/g, '?')
 			}),
 			'Accept-Ranges': 'bytes'
 		};

test/integration.test.js

@@ -1,5 +1,6 @@
 // Native
 const path = require('path');
+const os = require('os');
 
 // Packages
 const listen = require('test-listen');
@@ -1442,3 +1443,30 @@ test('prefer directory index.html over .html sibling when both 1.3/ and 1.3.html
 	expect(response.status).toBe(200);
 	expect(text).toBe(content);
 });
+
+test('serve a file whose name has non-ASCII characters', async () => {
+	const directory = await fs.mkdtemp(path.join(os.tmpdir(), 'serve-handler-'));
+	const names = ['bras\u00e3o.txt', 'DALL\u00b7E.png', '\u65e5\u672c\u8a9e.txt'];
+
+	try {
+		await Promise.all(names.map(name => fs.writeFile(path.join(directory, name), 'content')));
+
+		const url = await getUrl({
+			'public': directory
+		});
+
+		for (const name of names) {
+			const response = await fetch(`${url}/${encodeURIComponent(name)}`, {
+				timeout: 2000
+			});
+
+			expect(response.status).toBe(200);
+			expect(await response.text()).toBe('content');
+
+			const disposition = response.headers.get('content-disposition');
+			expect(disposition).toContain(`filename*=UTF-8''${encodeURIComponent(name)}`);
+		}
+	} finally {
+		await fs.remove(directory);
+	}
+});