fix(server): prevent service methods from mutating files in repository #1722
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Several service methods (BalanceFile, BuildFile, GetFileContents, SegmentFileID, FlattenBatches) were mutating files stored in the in-memory repository because FindFile() returns a direct pointer to the stored object. This caused data corruption where: - BalanceFile modified the original file's batches and ID, then stored the same pointer under a new key, leaving two keys pointing to one mutated object - Other methods called Create() on repository files, modifying their control totals The fix adds a cloneFile() helper that creates a deep copy via JSON serialization before any mutations. This ensures the original files in the repository remain unchanged. Added regression tests to verify original files are preserved after each operation
Summary of ChangesHello @MorganaFuture, I'm Gemini Code Assist1! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed! This pull request resolves a significant data integrity problem within the server's ACH file processing logic. Previously, various service methods were directly modifying file objects retrieved from the repository, causing unintended side effects and corrupting stored data. The core solution involves introducing a deep cloning mechanism for these files, ensuring that any operation performed on a file is done on a copy, thereby safeguarding the original data in the repository from mutation. This change enhances the robustness and reliability of file handling. Highlights
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Code Review
This pull request effectively addresses a critical data corruption bug by preventing service methods from mutating files in the in-memory repository. The introduction of a cloneFile helper to create deep copies of ach.File objects before modification is a solid approach. The implementation of cloneFile using JSON serialization is well-reasoned and correctly handles validation options. The accompanying regression tests are excellent and provide strong confidence in the fix for the modified methods.
However, I've identified a similar potential mutation issue in the MergeFiles method, which was not modified in this PR. It appears to retrieve files from the repository and use them directly without cloning, which could lead to the same data corruption this PR aims to solve. I strongly recommend applying the same cloning pattern to MergeFiles within this pull request to ensure all mutation paths are covered.
Additionally, there are minor inconsistencies in error handling in the modified methods that could be improved for better debuggability and consistency, which I've pointed out in specific comments.
| if err != nil { | ||
| return nil, fmt.Errorf("build file: error cloning file %s: %v", id, err) | ||
| } |
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For better error inspection and consistency with other parts of the code, it's preferable to use %w for error wrapping instead of %v. This allows for unwrapping the error chain using errors.Is or errors.As.
| if err != nil { | |
| return nil, fmt.Errorf("build file: error cloning file %s: %v", id, err) | |
| } | |
| if err != nil { | |
| return nil, fmt.Errorf("build file: error cloning file %s: %w", id, err) | |
| } | |
| if err != nil { | ||
| return nil, fmt.Errorf("problem cloning file %s: %v", id, err) | ||
| } |
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Similar to other parts of the code, using %w for error wrapping is preferred over %v for better error handling capabilities.
| if err != nil { | |
| return nil, fmt.Errorf("problem cloning file %s: %v", id, err) | |
| } | |
| if err != nil { | |
| return nil, fmt.Errorf("problem cloning file %s: %w", id, err) | |
| } | |
| if err != nil { | ||
| return nil, err | ||
| } |
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The error returned from cloneFile is not wrapped with any context. For consistency with the other methods modified in this PR and for better debuggability, it's a good practice to wrap this error. The other functions add context like which operation failed and for which file ID.
| if err != nil { | |
| return nil, err | |
| } | |
| if err != nil { | |
| return nil, fmt.Errorf("balance file: failed to clone file %s: %w", fileID, err) | |
| } | |
1 participant
Several service methods (BalanceFile, BuildFile, GetFileContents, SegmentFileID, FlattenBatches) were mutating files stored in the in-memory repository because FindFile() returns a direct pointer to the stored object.
This caused data corruption where:
The fix adds a cloneFile() helper that creates a deep copy via JSON serialization before any mutations. This ensures the original files in the repository remain unchanged.
Added regression tests to verify original files are preserved after each operation