fix: Improve HTTP error handling and fix null dereference in code fix provider

[thomhurst]

Summary

• Created HttpResponseException for detailed HTTP error information
• Added EnsureSuccessStatusCodeWithContentAsync extension method for better error messages
• Fixed null dereference in AsyncModuleCodeFixProvider

Changes

• New HttpResponseException.cs: Exception with status code, reason phrase, and response content
• New HttpResponseExtensions.cs: Extension method for HTTP response validation with content
• Updated Http.cs and Downloader.cs to use new extension method
• Fixed AsyncModuleCodeFixProvider.cs: Added null checks using FirstOrDefault()

Fixes #1574, Fixes #1550

Test plan

• Build succeeds
• Tests pass

🤖 Generated with Claude Code

[thomhurst]

Summary

Improves HTTP error handling with detailed exception messages and adds defensive null checks to the async module code fix provider.

Critical Issues

None found ✅

Suggestions

1. Consider adding tests for the new exception type

The new HttpResponseException class in src/ModularPipelines/Exceptions/HttpResponseException.cs provides valuable error context, but I don't see corresponding tests. Consider adding tests to verify:

• Exception message formatting with various combinations of status codes, reason phrases, and response content
• Content truncation behavior when response exceeds 2000 characters
• Proper handling of null values for optional properties

2. Minor optimization in HttpResponseExtensions.cs:70

The catch block swallows all exceptions when reading response content. While this is acceptable for robustness, consider at least catching specific exceptions like ObjectDisposedException or InvalidOperationException to make the intent clearer. The current approach is safe but slightly less explicit.

3. Code fix analyzer improvements look good

The defensive null checks in AsyncModuleCodeFixProvider.cs are well-implemented:

• Lines 69-72: Properly handles return statements without expressions
• Lines 80-87: Safely navigates the syntax tree with null checks
• The continue statements correctly skip malformed syntax instead of crashing

This addresses potential crashes when the code fix encounters edge cases like bare return; statements or malformed syntax trees.

Verdict

✅ APPROVE - No critical issues

The changes improve error diagnostics significantly by including response content in HTTP exceptions, making debugging much easier. The analyzer fixes add proper null safety for edge cases.