Remove \r\n for \n when writing to ostream (#24980)

src/Servers/IIS/AspNetCoreModuleV2/CommonLib/RedirectionOutput.cpp

@@ -77,7 +77,18 @@ void FileRedirectionOutput::Append(const std::wstring& text)
 {
     if (m_file.is_open())
     {
-        const auto multiByte = to_multi_byte_string(text, CP_UTF8);
+        auto multiByte = to_multi_byte_string(text, CP_UTF8);
+
+        // Writing \r\n to an ostream will cause two new lines to be written rather
+        // than one. Change all \r\n to \n.
+        std::string slashRslashN = "\r\n";
+        std::string slashN = "\n";
+        size_t start_pos = 0;
+        while ((start_pos = multiByte.find(slashRslashN, start_pos)) != std::string::npos) {
+            multiByte.replace(start_pos, slashRslashN.length(), slashN);
+            start_pos += slashN.length();
+        }
+
         m_file << multiByte;
     }
 }

src/Servers/IIS/IIS/test/Common.FunctionalTests/LogFileTests.cs

@@ -53,6 +53,8 @@ namespace Microsoft.AspNetCore.Server.IIS.FunctionalTests
             var contents = Helpers.ReadAllTextFromFile(Helpers.GetExpectedLogName(deploymentResult, _logFolderPath), Logger);
 
             Assert.Contains("TEST MESSAGE", contents);
+            Assert.DoesNotContain("\r\n\r\n", contents);
+            Assert.Contains("\r\n", contents);
         }
 
         // Move to separate file