avoid panic when opening FK files in convert-fk (propagate IO error)

[jmestwa-coder]

Summary

Fix a user-triggerable panic in the convert-fk CLI command when the input FK file is missing or cannot be opened.

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Architectural Changes

None.

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New Features

None.

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Improvements

• Ensures consistent error handling in convert-fk by propagating errors instead of panicking.
• Aligns convert-fk behavior with existing CLI patterns (e.g., convert-tpc).

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Bug Fixes

• Fixes a panic caused by:

  • unwrap() in the CLI layer (main.rs)
  • panic! on file open failure in the parser (parse_file)

• Missing or unreadable FK files now return a structured error instead of crashing the process.

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Reproduction

cargo run -p anise-cli -- convert-fk ./missing_fk.txt ./out.epa

Before

• Process panics due to unwrap() / panic!

After

• Returns a handled CLI error (no panic)

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Root Cause

• The parser (parse_file) panicked when File::open failed.
• The CLI (convert-fk) unconditionally unwrapped the result, propagating the panic to users.

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Fix

• Replace unwrap() in convert-fk with proper error propagation using .context(...) ?
• Replace panic! on file open in the parser with DataSetError::IO

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Testing and Validation

• Added an integration test:

  • Verifies that a missing FK file no longer causes a panic
  • Confirms graceful error handling through the CLI

• Manual validation:

  • Invalid input → returns error (no panic)
  • Valid input → unchanged behavior

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Scope

• Limited to the convert-fk path and its underlying parser behaviour
• No refactoring or unrelated changes
• No API or dependency changes

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Impact

• Prevents CLI crashes from invalid user input
• Improves robustness and reliability of file handling
• No behaviour change for valid inputs

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Notes

• This change specifically addresses the convert-fk path.
• Similar patterns in other commands can be addressed separately if needed.

[gemini-code-assist]

Code Review

This pull request improves error handling by replacing panics with proper error propagation when opening files and converting FK datasets. Specifically, it updates the anise-cli and the KPL parser to return Result types instead of using unwrap or panic!, and adds an integration test to verify that missing files are handled gracefully. I have no feedback to provide.

[ChristopherRabotin]

Thanks for your contribution!