🐛 Fix empty cookie header parsing and header value set (#1733)

Fixes #1730.

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- [x] I have read the
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- [x] I have searched for a similar pull request in the
[project](https://github.com/cfug/dio/pulls) and found none
- [x] I have updated this branch with the latest `main` branch to avoid
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- [x] I have added the required tests to prove the fix/feature I'm
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- [x] I have run the tests without failures
- [x] I have updated the `CHANGELOG.md` in the corresponding package

Author: AlexV525

plugins/cookie_manager/CHANGELOG.md

@@ -2,6 +2,7 @@
 
 ## Unreleased
 
+- Fix empty cookie parsing and header value set.
 - Improve code formats according to linter rules.
 
 ## 2.1.1
@@ -27,4 +28,4 @@
 
 ## 0.0.1 - 2019.9.17
 
-* A  cookie manager for Dio.
+* A cookie manager for Dio.

plugins/cookie_manager/lib/src/cookie_mgr.dart

@@ -35,12 +35,17 @@ class CookieManager extends Interceptor {
   @override
   void onRequest(RequestOptions options, RequestInterceptorHandler handler) {
     cookieJar.loadForRequest(options.uri).then((cookies) {
-      options.headers[HttpHeaders.cookieHeader] = getCookies([
+      final previousCookies =
+          options.headers[HttpHeaders.cookieHeader] as String?;
+      final newCookies = getCookies([
         ...cookies,
-        ...?options.headers[HttpHeaders.cookieHeader]
+        ...?previousCookies
             ?.split(';')
+            .where((e) => e.isNotEmpty)
             .map((c) => Cookie.fromSetCookieValue(c)),
       ]);
+      options.headers[HttpHeaders.cookieHeader] =
+          newCookies.isNotEmpty ? newCookies : null;
       handler.next(options);
     }).catchError((dynamic e, StackTrace s) {
       final err = DioError(requestOptions: options, error: e, stackTrace: s);

plugins/cookie_manager/test/cookies_test.dart

@@ -85,4 +85,30 @@ void main() {
 
     cookieManager.onRequest(options, mockRequestInterceptorHandler);
   });
+
+  group('Empty cookies', () {
+    test('not produced by default', () async {
+      final dio = Dio();
+      dio.interceptors.add(CookieManager(CookieJar()));
+      final response = await dio.get('http://www.gstatic.com/generate_204');
+      expect(response.requestOptions.headers[HttpHeaders.cookieHeader], null);
+    });
+
+    test('can be parsed', () async {
+      final dio = Dio();
+      dio.interceptors
+        ..add(
+          InterceptorsWrapper(
+            onRequest: (options, handler) {
+              // Write an empty cookie header.
+              options.headers[HttpHeaders.cookieHeader] = '';
+              handler.next(options);
+            },
+          ),
+        )
+        ..add(CookieManager(CookieJar()));
+      final response = await dio.get('http://www.gstatic.com/generate_204');
+      expect(response.requestOptions.headers[HttpHeaders.cookieHeader], null);
+    });
+  });
 }