fix(data): wrap MiniMax-M2 tool calls in <minimax:tool_call> tags

[he-yufeng]

What does this PR do?

MiniMaxM2ToolUtils.function_formatter emits the <invoke>...</invoke> blocks but never wraps them in the <minimax:tool_call>...</minimax:tool_call> tags. That is the wrapper the tool prompt (MINIMAX_M2_TOOL_PROMPT) tells the model to produce, and the same wrapper tool_extractor requires:

regex = re.compile(r"<minimax:tool_call>\s*(.+?)\s*</minimax:tool_call>", re.DOTALL)

So the assistant tool-call targets built during training don't match the format the model is taught to emit, and a round trip through function_formatter -> tool_extractor returns the raw string instead of the parsed calls.

Repro on current main:

tu = get_tool_utils("minimax2")
f = tu.function_formatter([FunctionCall("get_weather", json.dumps({"city": "NYC"}))])
# f has no <minimax:tool_call> wrapper
tu.tool_extractor(f)  # returns the raw string, extraction fails

The fix wraps the joined invoke blocks in the tags, matching both the prompt spec and the extractor:

return "<minimax:tool_call>\n" + "\n".join(function_texts) + "\n</minimax:tool_call>"

After the fix the round trip returns [FunctionCall(name='get_weather', arguments='{"city": "NYC"}')] for both single and parallel calls.

How I tested

Added regression tests in tests/data/test_formatter.py (single, parallel, extractor, round trip), mirroring the existing qwen/lfm2 cases.

python -m pytest tests/data/test_formatter.py -q   # 38 passed
ruff check                                          # clean

Before submitting

• Did you read the contributor guideline?
• Did you write any new necessary tests?

[gemini-code-assist]

Code Review

This pull request updates the function_formatter in src/llamafactory/data/tool_utils.py to wrap tool calls with <minimax:tool_call> tags. It also adds comprehensive unit tests in tests/data/test_formatter.py to verify the formatting, extraction, and round-trip behavior for the minimax2 tool format. There are no review comments, and I have no feedback to provide.

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