Code Review Error: Illegal Line Value After CCR

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Hey guys, let's dive into a pesky bug report related to a code review process within VS Code. Specifically, we're looking at an error that pops up with an "Illegal value for line" message after a Code Change Review (CCR). This issue was encountered when someone removed a method from a simple .tsx file. Let's break down the problem, the context, and how we might approach fixing it. It is also important to note that the problem is related to the SCMDiscussion category, which means that the problem is related to the Source Control Management (SCM) and the discussion around the code changes.

The Bug: "Illegal value for line"

The core of the issue is this error message: "Illegal value for line." It surfaces during a code review workflow, specifically after a CCR has been executed. A CCR, in this context, is likely a process where changes are reviewed and suggestions are provided. The error message indicates that a value is being passed that isn't valid for the line property within the review feedback. This leads to a breakdown in the review process. This error is triggered in the GitHub Review Agent. The agent is responsible for providing feedback and suggestions related to the code. The agent detected the removal of a function and provided a suggestion that contains the error "Illegal value for line".

The context here is crucial. It happened after removing a method in a .tsx file. The logs provided show the feedback generated by the code review agent. This agent correctly identifies the potential impact of removing a function and suggests either deprecating the function or ensuring all references are updated before removal. The problem arises when this suggestion is generated because it leads to the "Illegal value for line" error. The error is probably related to how the GitHub review agent is generating the feedback in response to the changes.

2025-10-14 11:55:28.682 [debug] [github review agent] response line: data: {"choices":null,"copilot_references":[{"type":"github.excluded-pull-request-comment","data":{"body":"Removing this function may break existing code that depends on it. Consider deprecating the function first or ensuring all references have been updated before removal.","comment_identifier":"9b414c24-cbdf-47e5-8328-1a7113d4b444","exclusion_reason":"no_matched_diff_hunk","line":38,"path":"src/utils/github.ts","problem_type":"maintainability","side":"RIGHT"},"id":"","is_implicit":false,"metadata":{"display_name":"","display_icon":"","display_url":""}}],"id":null}
2025-10-14 11:55:28.683 [debug] [github review agent] response line: 
2025-10-14 11:55:28.691 [debug] [github review agent] response line: data: [DONE]
2025-10-14 11:55:28.691 [debug] [github review agent] response line:

This log output shows that the agent is attempting to provide a suggestion with a line property, which is likely intended to highlight the specific line of code in question. The fact that an "Illegal value" is present suggests something is wrong with how that value is being calculated, formatted, or passed to the review interface.

Debugging Steps and Troubleshooting

To fix this bug, you'll need a combination of detective work and technical knowledge. Here are some of the steps you can take:

  • Inspect the Code Review Agent: The primary focus should be on how the GitHub review agent generates the feedback. Look into the code that calculates or determines the line value. Does it account for line numbers accurately after the method removal? Does it handle the situation where lines shift due to the code changes? You might need to examine the source code related to the code review extension or tool being used.
  • Review the line Property: Understand the requirements for the line property. What kind of values are accepted? What's the acceptable range? Are there any special formats or conditions that must be met? Knowing these details will help you spot incorrect values.
  • Test with different scenarios: Try removing methods in different parts of your code and observe the error. The error may only be caused by the function at a specific place. This may narrow down where the bug happens.
  • Check the Line Number Calculation: Determine how the agent calculates the line number. Is it based on the diff? Is it taking into account the code changes that were made? Is it using any offset? It is likely that the line number that is being used by the agent is wrong, it should be changed.

VS Code, OS, and System Info

  • VS Code Version: Code - Insiders 1.106.0-insider (Universal) (bf56edffb59c43fa0de636c3aa1d548770b168b8, 2025-10-13T05:02:32.230Z). This version might have known bugs that can cause the error, so ensure it is the latest version.
  • OS Version: Darwin arm64 24.6.0. The operating system and its version could contribute to this error. Test and check how the agent works on different operating systems.
  • System Information: The system information provides details about your hardware and the environment. This includes things like the number of CPUs, the GPU status, and the memory. This might not be directly related to the issue, but it's important to have.

Potential Causes and Solutions

Let's brainstorm some potential causes and corresponding solutions:

  • Incorrect Line Number Calculation: This is the most likely cause. The agent may not accurately calculate the line number after code changes. If you removed a method, the lines following the method would shift. The solution is to update the line number calculation logic.
  • Formatting Errors: Perhaps the line value is not formatted correctly. For example, it should be an integer, but it's being passed as a string. Check and correct the formatting to ensure the line value is valid.
  • Out-of-Range Values: The line property may be getting an out-of-range value. The line value must fall within the range of existing code lines. Check the logic that validates the line number and make sure that it's using the correct number.
  • Bug in the Review Extension: There may be a bug in the code review extension that is responsible for processing the feedback. In this case, you may need to wait for an update that fixes the bug.

Conclusion and Next Steps

This "Illegal value for line" error during code review highlights an issue in how line numbers are handled within the review process. To resolve it, we need a deep dive into the code review agent, with a particular focus on how line numbers are calculated and validated. This may include debugging the code that provides the feedback. It's also important to confirm whether the issue is isolated to a specific type of change (method removal, in this case) or if it occurs in other scenarios. By systematically investigating the code and the feedback process, you should be able to pinpoint the root cause of the error and get the code review workflow back on track. If the issue is complex, you may consider reaching out to the developers of the code review extension or tool for assistance.