Enhance server creation logic and add unit tests

Updated the `MakeServers` method to include a check for `defaultUrl` when creating servers. The method now returns early if all relevant parameters are null, and the host assignment from `defaultUrl` now preserves the port.

Added new unit tests in `OpenApiServerTests.cs` to ensure that base URLs with ports are correctly handled. Tests cover scenarios for base URLs with a port, with a port and path, and with a non-standard port.

Author: Mahdi Golestan

src/Microsoft.OpenApi.Readers/V2/OpenApiDocumentDeserializer.cs

@@ -145,8 +145,8 @@ private static void MakeServers(IList<OpenApiServer> servers, ParsingContext con
                 basePath = "/";
             }
 
-            // If nothing is provided, don't create a server
-            if (host == null && basePath == null && schemes == null)
+            // If nothing is provided and there's no defaultUrl, don't create a server
+            if (host == null && basePath == null && schemes == null && defaultUrl == null)
             {
                 return;
             }
@@ -161,7 +161,7 @@ private static void MakeServers(IList<OpenApiServer> servers, ParsingContext con
             // Fill in missing information based on the defaultUrl
             if (defaultUrl != null)
             {
-                host = host ?? defaultUrl.GetComponents(UriComponents.NormalizedHost, UriFormat.SafeUnescaped);
+                host = host ?? defaultUrl.GetComponents(UriComponents.Host | UriComponents.Port, UriFormat.SafeUnescaped);
                 basePath = basePath ?? defaultUrl.GetComponents(UriComponents.Path, UriFormat.SafeUnescaped);
                 schemes = schemes ?? new List<string> { defaultUrl.GetComponents(UriComponents.Scheme, UriFormat.SafeUnescaped) };
             }

test/Microsoft.OpenApi.Readers.Tests/V2Tests/OpenApiServerTests.cs

@@ -323,5 +323,74 @@ public void InvalidHostShouldYieldError()
                     SpecificationVersion = OpenApiSpecVersion.OpenApi2_0
                 });
         }
+
+        [Fact]
+        public void BaseUrlWithPortShouldPreservePort()
+        {
+            var input =
+                """
+                swagger: 2.0
+                info:
+                  title: test
+                  version: 1.0.0
+                paths: {}
+                """;
+            var reader = new OpenApiStringReader(new()
+            {
+                BaseUrl = new("http://demo.testfire.net:8080")
+            });
+
+            var doc = reader.Read(input, out var diagnostic);
+
+            var server = doc.Servers.First();
+            Assert.Single(doc.Servers);
+            Assert.Equal("http://demo.testfire.net:8080", server.Url);
+        }
+
+        [Fact]
+        public void BaseUrlWithPortAndPathShouldPreservePort()
+        {
+            var input =
+                """
+                swagger: 2.0
+                info:
+                  title: test
+                  version: 1.0.0
+                paths: {}
+                """;
+            var reader = new OpenApiStringReader(new()
+            {
+                BaseUrl = new("http://demo.testfire.net:8080/swagger/properties.json")
+            });
+
+            var doc = reader.Read(input, out var diagnostic);
+
+            var server = doc.Servers.First();
+            Assert.Single(doc.Servers);
+            Assert.Equal("http://demo.testfire.net:8080/swagger/properties.json", server.Url);
+        }
+
+        [Fact]
+        public void BaseUrlWithNonStandardPortShouldPreservePort()
+        {
+            var input =
+                """
+                swagger: 2.0
+                info:
+                  title: test
+                  version: 1.0.0
+                paths: {}
+                """;
+            var reader = new OpenApiStringReader(new()
+            {
+                BaseUrl = new("https://api.example.com:9443/v1/openapi.yaml")
+            });
+
+            var doc = reader.Read(input, out var diagnostic);
+
+            var server = doc.Servers.First();
+            Assert.Single(doc.Servers);
+            Assert.Equal("https://api.example.com:9443/v1/openapi.yaml", server.Url);
+        }
     }
 }