Fix: Prevent Errors in Header Processing and Encode URLs Properly

packages/api-fetch/src/middlewares/preloading.js

@@ -68,15 +68,40 @@ function createPreloadingMiddleware( preloadedData ) {
  * @return {Promise<any>} Promise with the response.
  */
 function prepareResponse( responseData, parse ) {
-	return Promise.resolve(
-		parse
-			? responseData.body
-			: new window.Response( JSON.stringify( responseData.body ), {
-					status: 200,
-					statusText: 'OK',
-					headers: responseData.headers,
-			  } )
-	);
+	if ( parse ) {
+		return Promise.resolve( responseData.body );
+	}
+
+	try {
+		return Promise.resolve(
+			new window.Response( JSON.stringify( responseData.body ), {
+				status: 200,
+				statusText: 'OK',
+				headers: responseData.headers,
+			} )
+		);
+	} catch {
+		// See: https://github.com/WordPress/gutenberg/issues/67358#issuecomment-2621163926.
+		Object.entries( responseData.headers ).forEach( ( [ key, value ] ) => {
+			if ( key.toLowerCase() === 'link' ) {
+				responseData.headers[ key ] = value.replace(
+					/<([^>]+)>/,
+					( /** @type {any} */ _, /** @type {string} */ url ) =>
+						`<${ encodeURI( url ) }>`
+				);
+			}
+		} );
+
+		return Promise.resolve(
+			parse
+				? responseData.body
+				: new window.Response( JSON.stringify( responseData.body ), {
+						status: 200,
+						statusText: 'OK',
+						headers: responseData.headers,
+				  } )
+		);
+	}
 }
 
 export default createPreloadingMiddleware;

packages/api-fetch/src/middlewares/test/preloading.js

@@ -265,6 +265,57 @@ describe( 'Preloading Middleware', () => {
 		expect( secondMiddleware ).toHaveBeenCalledTimes( 1 );
 	} );
 
+	it( 'should not throw an error when non-ASCII headers are present', async () => {
+		const noResponseMock = 'undefined' === typeof window.Response;
+		if ( noResponseMock ) {
+			window.Response = class {
+				constructor( body, options ) {
+					this.body = JSON.parse( body );
+					this.headers = options.headers;
+
+					// Check for non-ASCII characters in headers
+					for ( const [ key, value ] of Object.entries(
+						this.headers || {}
+					) ) {
+						if ( /[^\x00-\x7F]/.test( value ) ) {
+							throw new Error(
+								`Invalid non-ASCII character found in header: ${ key }`
+							);
+						}
+					}
+				}
+			};
+		}
+
+		const data = {
+			body: 'Hello',
+			headers: {
+				Link: '<http://example.com/ویدیو/example>; rel="alternate"; type=text/html',
+			},
+		};
+
+		const preloadedData = {
+			'wp/v2/example': data,
+		};
+
+		const preloadingMiddleware =
+			createPreloadingMiddleware( preloadedData );
+
+		const requestOptions = {
+			method: 'GET',
+			path: 'wp/v2/example',
+			parse: false,
+		};
+
+		await expect(
+			preloadingMiddleware( requestOptions, () => {} )
+		).resolves.not.toThrow();
+
+		if ( noResponseMock ) {
+			delete window.Response;
+		}
+	} );
+
 	describe.each( [ [ 'GET' ], [ 'OPTIONS' ] ] )( '%s', ( method ) => {
 		describe.each( [
 			[ 'all empty', {} ],