Add some additional header tests

pkgs/http/lib/src/base_response.dart

@@ -26,6 +26,26 @@ abstract class BaseResponse {
 
   // TODO(nweiz): automatically parse cookies from headers
 
+  /// The HTTP headers returned by the server.
+  ///
+  /// The header names are converted to lowercase and stored with their
+  /// associated header values.
+  ///
+  /// If the server returns multiple headers with the same name then the header
+  /// values will be associated with a single key and seperated by commas and
+  /// possibly whitespace. For example:
+  /// ```dart
+  /// // HTTP/1.1 200 OK
+  /// // Fruit: Apple
+  /// // Fruit: Banana
+  /// // Fruit: Grape
+  /// final values = response.headers['fruit']!.split(RegExp(r'\s*,\s*'));
+  /// // values = ['Apple', 'Banana', 'Grape']
+  /// ```
+  ///
+  /// If a header value contains whitespace then that whitespace may be replaced
+  /// by a single space. Leading and trailing whitespace in header values are
+  /// always removed.
   // TODO(nweiz): make this a HttpHeaders object.
   final Map<String, String> headers;
 

pkgs/http_client_conformance_tests/lib/src/response_headers_tests.dart

@@ -30,24 +30,47 @@ void testResponseHeaders(Client client) async {
       expect(response.headers['foo'], 'bar');
     });
 
+    test('UPPERCASE header name', () async {
+      // RFC 2616 14.44 states that header field names are case-insensitive.
+      // http.Client canonicalizes field names into lower case.
+      httpServerChannel.sink.add('FOO: bar\r\n');
+
+      final response = await client.get(Uri.http(host, ''));
+      expect(response.headers['foo'], 'bar');
+    });
+
     test('UPPERCASE header value', () async {
       httpServerChannel.sink.add('foo: BAR\r\n');
 
       final response = await client.get(Uri.http(host, ''));
-      // RFC 2616 14.44 states that header field names are case-insensitive.
-      // http.Client canonicalizes field names into lower case.
       expect(response.headers['foo'], 'BAR');
     });
 
     test('space surrounding header value', () async {
       httpServerChannel.sink.add('foo: \t BAR \t \r\n');
 
       final response = await client.get(Uri.http(host, ''));
-      // RFC 2616 14.44 states that header field names are case-insensitive.
-      // http.Client canonicalizes field names into lower case.
       expect(response.headers['foo'], 'BAR');
     });
 
+    test('space in header value', () async {
+      httpServerChannel.sink.add('foo: BAR BAZ\r\n');
+
+      final response = await client.get(Uri.http(host, ''));
+      expect(response.headers['foo'], 'BAR BAZ');
+    });
+
+    test('multiple spaces in header value', () async {
+      // RFC 2616 4.2 allows LWS between header values to be replace with a
+      // single space.
+      // See https://datatracker.ietf.org/doc/html/rfc2616#section-4.2
+      httpServerChannel.sink.add('foo: BAR  \t   BAZ\r\n');
+
+      final response = await client.get(Uri.http(host, ''));
+      expect(
+          response.headers['foo'], matches(RegExp('BAR {0,2}[ \t] {0,3}BAZ')));
+    });
+
     test('multiple headers', () async {
       httpServerChannel.sink
           .add('field1: value1\r\n' 'field2: value2\r\n' 'field3: value3\r\n');
@@ -130,5 +153,30 @@ void testResponseHeaders(Client client) async {
             client.get(Uri.http(host, '')), throwsA(isA<ClientException>()));
       });
     });
+
+    group('folded headers', () {
+      // RFC2616 says that HTTP Headers can be split across multiple lines.
+      // See https://datatracker.ietf.org/doc/html/rfc2616#section-2.2
+      test('leading space', () async {
+        httpServerChannel.sink.add('foo: BAR\r\n BAZ\r\n');
+
+        final response = await client.get(Uri.http(host, ''));
+        expect(response.headers['foo'], 'BAR BAZ');
+      },
+          skip: 'Enable after https://github.com/dart-lang/sdk/issues/53185 '
+              'is fixed');
+
+      test('extra whitespace', () async {
+        httpServerChannel.sink.add('foo: BAR   \t   \r\n   \t   BAZ \t \r\n');
+
+        final response = await client.get(Uri.http(host, ''));
+        // RFC 2616 4.2 allows LWS between header values to be replace with a
+        // single space.
+        expect(
+            response.headers['foo'],
+            allOf(matches(RegExp(r'BAR {0,3}[ \t]? {0,7}[ \t]? {0,3}BAZ')),
+                contains(' ')));
+      });
+    });
   });
 }