Add parsing of zero port for unknown Uri scheme (#40986)

Fixes #37865

Author: CarnaViire

src/libraries/System.Private.Uri/src/System/Uri.cs

@@ -2265,7 +2265,7 @@ private unsafe void CreateUriInfo(Flags cF)
                                 }
                             }
                         }
-                        if (notEmpty && info.Offset.PortValue != port)
+                        if (notEmpty && _syntax.DefaultPort != port)
                         {
                             info.Offset.PortValue = (ushort)port;
                             cF |= Flags.NotDefaultPort;

src/libraries/System.Private.Uri/tests/FunctionalTests/UriGetComponentsTest.cs

@@ -61,11 +61,11 @@ public void GetComponents_UnknownScheme_ComponentsUnaffected()
             testUri = new Uri("abc://127.00.000.001:01234");
             Assert.Equal("127.00.000.001:1234", testUri.Authority);
 
-            // Known limitation: port 0 is ignored.
+            // Port 0 is parsed correctly.
             testUri = new Uri("cbd://127.00.1.2:0000");
-            Assert.Equal("127.00.1.2", testUri.Authority);
+            Assert.Equal("127.00.1.2:0", testUri.Authority);
             testUri = new Uri("cbd://127.00.1.2:0");
-            Assert.Equal("127.00.1.2", testUri.Authority);
+            Assert.Equal("127.00.1.2:0", testUri.Authority);
 
             testUri = new Uri("eb://[0000::01:123.32.123.23]/dir");
             Assert.Equal("[::1:7b20:7b17]", testUri.Authority);

src/libraries/System.Private.Uri/tests/FunctionalTests/UriTests.cs

@@ -818,5 +818,23 @@ public static void FilePathHandlesNonAscii(string uriString, string toString, st
             Assert.Equal(absoluteUri, uri2.AbsoluteUri);
             Assert.Equal(localPath, uri2.LocalPath);
         }
+
+        public static IEnumerable<object[]> ZeroPortIsParsedForBothKnownAndUnknownSchemes_TestData()
+        {
+            yield return new object[] { "http://example.com:0", 0, false };
+            yield return new object[] { "http://example.com", 80, true };
+            yield return new object[] { "rtsp://example.com:0", 0, false };
+            yield return new object[] { "rtsp://example.com", -1, true };
+        }
+
+        [Theory]
+        [MemberData(nameof(ZeroPortIsParsedForBothKnownAndUnknownSchemes_TestData))]
+        public static void ZeroPortIsParsedForBothKnownAndUnknownSchemes(string uriString, int port, bool isDefaultPort)
+        {
+            Uri.TryCreate(uriString, UriKind.Absolute, out var uri);
+            Assert.Equal(port, uri.Port);
+            Assert.Equal(isDefaultPort, uri.IsDefaultPort);
+            Assert.Equal(uriString + "/", uri.ToString());
+        }
     }
 }