Improve invalid enum error message

[BugelNiels]

Updates the enum_to_string function to have a more elaborate error messages. I had to move around the get_enumerators() and related functions as one of them was needed to implement this fix (get_enumerator_array). I figured this was cleaner than forward declaring it in the same file.

I have also added a few basic tests to verify the error behaviour. Let me know if additional tests are needed here.

Fixes #605

[gemini-code-assist]

Summary of Changes

Hello @BugelNiels, 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 significantly improves the diagnostic feedback for users attempting to convert invalid strings to enum types. By generating a comprehensive error message that includes the expected enum values, it makes debugging and understanding conversion failures much easier. The changes also involve a minor refactoring of internal enum utility functions to facilitate this enhancement, along with the addition of robust test cases.

Highlights

• Improved Enum Error Messages: The string_to_enum function now provides more descriptive error messages when an invalid enum value is encountered, listing all valid enumerator options.
• Refactoring of Enum Helper Functions: Several get_ helper functions within include/rfl/enums.hpp were reordered to ensure get_enumerator_array is available for use in the improved error message generation.
• New Error Message Tests: Dedicated tests have been added to tests/json/test_enum_error_messages.cpp to validate the behavior and content of the new error messages for various invalid enum inputs.

Changelog

• include/rfl/enums.hpp
  • Relocated get_enumerators, get_underlying_enumerators, get_enumerator_array, get_underlying_enumerator_array, and get_enum_range functions to an earlier position in the file.
  • Enhanced the error message generated by string_to_enum for invalid inputs to include the provided invalid value and a list of all valid enum options.
• tests/json/test_enum_error_messages.cpp
  • Added a new test file to specifically test the improved error messages for string_to_enum.
  • Included tests for invalid, empty, and case-sensitive string inputs to ensure correct error reporting.

Activity

• Author BugelNiels initiated the pull request to improve error messages for invalid enum conversions.
• The author refactored the placement of get_enumerators() and related functions to enable the fix.
• Basic tests were added to verify the error behavior, with the author inviting feedback on the need for additional tests.
• This PR addresses and fixes issue Improve error message when an invalid enum value is provided. #605.

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Code Review

This pull request improves the error message for invalid enum string conversions by listing the available enum values. The change is well-implemented and includes new tests to verify the behavior. I've made a few suggestions to improve code clarity and fix a minor typo in the tests.

[BugelNiels]

Replaced the std::ostringstream with regular strings so that it doesn't need an additional import. The currently failing tests all seem to be due to transient download failures.