Address code review feedback

- Fix temp file creation logic in UserSecretsManagerFactory to write content before moving
- Change JsonFlattener from public to internal (consistent with Internal namespace)
- Remove trailing empty line in test file

All tests still passing after fixes.

Co-authored-by: davidfowl <[email protected]>

Author: Copilot

src/Aspire.Hosting/Publishing/Internal/JsonFlattener.cs

@@ -8,7 +8,7 @@ namespace Aspire.Hosting.Publishing.Internal;
 /// <summary>
 /// Provides utility methods for flattening and unflattening JSON objects using colon-separated keys.
 /// </summary>
-public static class JsonFlattener
+internal static class JsonFlattener
 {
     /// <summary>
     /// Flattens a JsonObject using colon-separated keys for configuration compatibility.

src/Aspire.Hosting/UserSecrets/UserSecretsManagerFactory.cs

@@ -253,15 +253,19 @@ private void Save(Dictionary<string, string?> secrets)
                 contents[secret.Key] = secret.Value;
             }
 
+            var json = contents.ToJsonString(s_jsonSerializerOptions);
+
             // Create a temp file with the correct Unix file mode before moving it to the expected path.
             if (!OperatingSystem.IsWindows())
             {
                 var tempFilename = Path.GetTempFileName();
+                File.WriteAllText(tempFilename, json, Encoding.UTF8);
                 File.Move(tempFilename, FilePath, overwrite: true);
             }
-
-            var json = contents.ToJsonString(s_jsonSerializerOptions);
-            File.WriteAllText(FilePath, json, Encoding.UTF8);
+            else
+            {
+                File.WriteAllText(FilePath, json, Encoding.UTF8);
+            }
         }
 
         private async Task SaveAsync(Dictionary<string, string?> secrets, CancellationToken cancellationToken)
@@ -272,15 +276,19 @@ private async Task SaveAsync(Dictionary<string, string?> secrets, CancellationTo
                 contents[secret.Key] = secret.Value;
             }
 
+            var json = contents.ToJsonString(s_jsonSerializerOptions);
+
             // Create a temp file with the correct Unix file mode before moving it to the expected path.
             if (!OperatingSystem.IsWindows())
             {
                 var tempFilename = Path.GetTempFileName();
+                await File.WriteAllTextAsync(tempFilename, json, Encoding.UTF8, cancellationToken).ConfigureAwait(false);
                 File.Move(tempFilename, FilePath, overwrite: true);
             }
-
-            var json = contents.ToJsonString(s_jsonSerializerOptions);
-            await File.WriteAllTextAsync(FilePath, json, Encoding.UTF8, cancellationToken).ConfigureAwait(false);
+            else
+            {
+                await File.WriteAllTextAsync(FilePath, json, Encoding.UTF8, cancellationToken).ConfigureAwait(false);
+            }
         }
 
         private void EnsureUserSecretsDirectory()

tests/Aspire.Hosting.Tests/UserSecretsParameterDefaultTests.cs

@@ -261,4 +261,3 @@ public override void WriteToManifest(ManifestPublishingContext context)
         }
     }
 }
-