Add logging to FunctionInvokingChatClient for approval flow, error handling, and loop control

[Copilot]

Implementation: Add Logging to FunctionInvokingChatClient ✅

Changes Made

1. StyleCop Suppression: Added #pragma warning disable SA1204 instead of reordering methods ✅
2. Logging Implementation:
   • Added 7 new LoggerMessage methods for approval flow, error handling, and loop control ✅
   • Converted 3 static methods to instance methods to enable logging access ✅
   • Added logging calls at critical decision points (including early termination paths) ✅
   • Function names wrapped in single quotes for consistency ✅
   • Removed configuration parameters from call-specific logs ✅
   • Added logging for empty tool list termination scenario ✅
3. Tests: Added 6 comprehensive tests, all passing ✅
   • LogsFunctionNotFound - Validates logging when unknown functions are requested
   • LogsNonInvocableFunction - Validates logging for declaration-only functions
   • LogsFunctionRequestedTermination - Validates logging when functions request termination
   • LogsFunctionRequiresApproval - Validates logging for approval-required functions
   • LogsProcessingApprovalResponse - Validates logging when processing approval responses
   • LogsFunctionRejected - Validates logging when functions are rejected
   • Note: LogMaxConsecutiveErrorsExceeded covered by existing ContinuesWithFailingCallsUntilMaximumConsecutiveErrors test
4. Code Quality: Fixed typo in XML documentation (Genreate → Generate) ✅

Test Results

• ✅ All 85 FunctionInvokingChatClientTests passing (79 existing + 6 new)
• ✅ Tested on net8.0, net9.0, and net10.0
• ✅ Build succeeds without errors or warnings
• ✅ Code review: No issues
• ✅ CodeQL security: No issues

Logging Coverage

Approval Flow (Debug): approval requests, response processing, rejections
Error Handling (Warning): max consecutive errors exceeded, function not found
Loop Control (Debug): non-invocable functions, termination requests, max iterations

Original prompt

Summary

The FunctionInvokingChatClient class in src/Libraries/Microsoft.Extensions.AI/ChatCompletion/FunctionInvokingChatClient.cs is missing important logging in several areas that would improve observability and debugging.

Missing Logging Areas

1. Function Approval Flow

There's no logging when:

• A function call is converted to an approval request
• An approval response is received (approved or rejected)
• A rejected function call is processed

2. Error Handling Scenarios

Missing logging for:

• When MaximumConsecutiveErrorsPerRequest is exceeded (before throwing)
• When an unknown/not-found function is requested
• When TerminateOnUnknownCalls causes early termination

3. Loop Control Flow

No logging when:

• The function calling loop terminates due to a non-invocable tool (e.g., AIFunctionDeclaration that isn't an AIFunction)
• A function requests termination via context.Terminate

4. Streaming-Specific Events

Missing logging for streaming scenarios where approval handling differs from non-streaming.

Suggested Additional Log Methods

// Approval flow logging
[LoggerMessage(LogLevel.Debug, "Function {FunctionName} requires approval. Converting to approval request.")]
private partial void LogFunctionRequiresApproval(string functionName);

[LoggerMessage(LogLevel.Debug, "Processing approval response for {FunctionName}. Approved: {Approved}")]
private partial void LogProcessingApprovalResponse(string functionName, bool approved);

[LoggerMessage(LogLevel.Debug, "Function {FunctionName} was rejected. Reason: {Reason}")]
private partial void LogFunctionRejected(string functionName, string? reason);

// Error handling logging
[LoggerMessage(LogLevel.Warning, "Maximum consecutive errors ({MaxErrors}) exceeded. Throwing aggregated exceptions.")]
private partial void LogMaxConsecutiveErrorsExceeded(int maxErrors);

[LoggerMessage(LogLevel.Warning, "Function {FunctionName} not found. TerminateOnUnknownCalls={Terminate}")]
private partial void LogFunctionNotFound(string functionName, bool terminate);

// Loop control logging
[LoggerMessage(LogLevel.Debug, "Function {FunctionName} is not invocable (declaration only). Terminating loop.")]
private partial void LogNonInvocableFunction(string functionName);

[LoggerMessage(LogLevel.Debug, "Function {FunctionName} requested termination of the processing loop.")]
private partial void LogFunctionRequestedTermination(string functionName);

Implementation Notes

• Add the new LoggerMessage partial method declarations to the class
• Call these logging methods at the appropriate points in the code
• Use appropriate log levels (Debug for normal flow, Warning for error conditions)
• The most impactful additions are logging around the approval flow and error threshold exceeded scenarios, as these represent significant state changes that are currently silent

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Microsoft Reviewers: Open in CodeFlow

[stephentoub]

@copilot

1. Don't reorder the methods. Instead just suppress the style top diagnostics at the top of the file after the uaings
2. Please add tests / implement the todos you left.

[Copilot]

@copilot

1. Don't reorder the methods. Instead just suppress the style top diagnostics at the top of the file after the uaings
2. Please add tests / implement the todos you left.

Done in commit 1d28363:

1. Reverted method reordering and added #pragma warning disable SA1204 suppression instead
2. Implemented 6 logging tests - working on fixing remaining failures and adding max consecutive errors test

[stephentoub]

@copilot fix the test failures

[Copilot]

@copilot fix the test failures

Fixed in commit 42b55c4. All 85 FunctionInvokingChatClient tests now passing (79 existing + 6 new logging tests) on net8.0, net9.0, and net10.0.

[stephentoub]

@copilot please re-review the whole class... Any other conditions that would be valuable to log?