fix(core): handle None arguments in parse_tool_call

[edlsh]

Description

When an LLM calls a parameter-less tool, some providers return None or an empty string for the arguments field instead of valid JSON like "{}". This caused parse_tool_call to raise a TypeError because json.loads(None) is not valid.

Problem

raw_tool_call = {
    'function': {'arguments': None, 'name': 'orderStatus'},
    'id': 'chatcmpl-tool-8b1f759d874b412e931e64cf6f57bdcc',
    'type': 'function'
}
parse_tool_call(raw_tool_call, return_id=True)
# TypeError: the JSON object must be str, bytes or bytearray, not NoneType

Solution

Added a check to handle None and empty string arguments by treating them as an empty object {}, allowing parameter-less tools to be parsed correctly.

This is a minimal, targeted fix that:

• Handles None arguments → returns {}
• Handles empty string "" arguments → returns {}
• Preserves existing behavior for valid JSON arguments
• Preserves existing error handling for invalid JSON

Testing

Added 4 new unit tests:

• test_parse_tool_call_with_none_arguments - reproduces the original bug
• test_parse_tool_call_with_empty_string_arguments - handles empty strings
• test_parse_tool_call_with_valid_arguments - ensures normal behavior works
• test_parse_tool_call_partial_mode_with_none_arguments - verifies partial mode behavior

All existing tests continue to pass.

---

AI Disclosure: This PR was developed with assistance from Claude (AI).

Fixes #34123

[codspeed-hq]

CodSpeed Performance Report

Merging #34242 will not alter performance

_{Comparing edlsh:fix/core-parse-tool-call-none-arguments (94287f4) with master (8a5f463)}

⚠️ Unknown Walltime execution environment detected

Using the Walltime instrument on standard Hosted Runners will lead to inconsistent data.

For the most accurate results, we recommend using CodSpeed Macro Runners: bare-metal machines fine-tuned for performance measurement consistency.

Summary

✅ 13 untouched
⏩ 21 skipped¹

Footnotes

1. 21 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩