bug: GenerationLog.print_summary() crashes with stats.total_duration or activated_rail.duration None values

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Python version (python --version)

Python 3.13.2

Operating system/version

MacOS 26.5.2

NeMo-Guardrails version (if you must use a specific version and not the latest

0.24

Describe the bug

The stats.total_duration and activated_rail.duration fields are Optional[float] fields.

The GenerationLog.print_summary() doesn't have None-guards for all these fields, which will throw errors when it tries to print None with a float format.

Steps To Reproduce

Create

Expected Behavior

GenerationLog.print_summary() should correctly guard None values rather than crashing. With the option of OTEL tracing, the value of print_summary() is debatable

Actual Behavior

Create the script below in print_summary.py, and run it using uv run --locked python print_summary.py

"""Reproduce TypeError in GenerationLog.print_summary() on None duration fields.

print_summary() (nemoguardrails/rails/llm/options.py) formats several
Optional[float] duration fields with ``:.2f`` without guarding against None, so
any log carrying a None duration raises:

    TypeError: unsupported format string passed to NoneType.__format__

There are two independent, unguarded crash points:

  1. GenerationStats.total_duration  (options.py ~line 318)
     This field DEFAULTS to None, so a freshly built GenerationLog whose stats
     were never populated crashes on the very first print, before any rail is
     inspected.

  2. ActivatedRail.duration  (options.py ~line 370, the "Detailed stats" loop)
     ActivatedRail.duration is Optional[float] and tool rails come through with
     duration=None, so they crash the per-rail loop even when the stats block is
     fully populated.

Both are reproduced below; each is caught so the script runs to completion and
prints a full traceback pointing at the exact failing line.

Run:  python print_summary.py
"""

import sys
import traceback

import nemoguardrails
from nemoguardrails.rails.llm.options import (
    ActivatedRail,
    ExecutedAction,
    GenerationLog,
    GenerationStats,
)


def crash_1_total_duration() -> None:
    """GenerationStats.total_duration defaults to None and crashes line ~318.

    The activated rail here carries a valid duration; only stats is left at its
    default, isolating total_duration as the field that crashes.
    """
    log = GenerationLog(
        activated_rails=[
            ActivatedRail(type="tool_output", name="tool output check", duration=0.5),
        ],
    )
    log.print_summary()


def crash_2_activated_rail_duration() -> None:
    """A tool rail with duration=None crashes the detailed-stats loop, line ~370.

    stats.total_duration is populated so execution gets past crash point #1 and
    reaches the per-rail loop, isolating ActivatedRail.duration as the field
    that crashes.
    """
    log = GenerationLog(
        activated_rails=[
            ActivatedRail(
                type="tool_output",
                name="tool output check",
                executed_actions=[ExecutedAction(action_name="tool_output_check")],
                duration=None,
            ),
        ],
        stats=GenerationStats(total_duration=0.5),
    )
    log.print_summary()


def run(label: str, fn) -> None:
    print(f"\n{'=' * 72}\n{label}\n{'=' * 72}")
    try:
        fn()
    except TypeError:
        print("REPRODUCED - TypeError raised:\n")
        traceback.print_exc()
    else:
        print("No error raised - bug NOT reproduced.")


if __name__ == "__main__":
    print(f"Python:        {sys.version.split()[0]}")
    print(f"nemoguardrails: {getattr(nemoguardrails, '__version__', 'unknown')}")

    run(
        "Crash 1: GenerationStats.total_duration is None (options.py ~line 318)",
        crash_1_total_duration,
    )
    run(
        "Crash 2: ActivatedRail.duration is None (options.py ~line 370)",
        crash_2_activated_rail_duration,
    )