fix: guard against None resource_limit in _max_throughput_from_resources

[kuishou68]

Closes #62601

Problem

_max_throughput_from_resources() calls getattr(resource_limits, resource_name) to get CPU/GPU/memory limits. When a resource is unconstrained, ExecutionResources stores None for that field. The division resource_limit / resource_cost_per_unit_throughput then raises:

TypeError: unsupported operand type(s) for /: 'NoneType' and 'float'

Fix

Add a resource_limit is not None guard — a None limit means the resource is unconstrained and should not bound max_throughput:

# Before
if resource_cost_per_unit_throughput > 0:
    max_throughput = min(max_throughput, resource_limit / resource_cost_per_unit_throughput)

# After
if resource_cost_per_unit_throughput > 0 and resource_limit is not None:
    max_throughput = min(max_throughput, resource_limit / resource_cost_per_unit_throughput)

[gemini-code-assist]

Code Review

This pull request adds a null check for resource_limit in the throughput solver to prevent a TypeError when calculating maximum throughput. The review feedback points out that a similar TypeError could occur at line 100 if resource requirements are unset, and suggests handling those cases as well as optimizing the check's placement for better efficiency.

[gemini-code-assist]

While this change correctly guards against None in resource_limit, a similar TypeError is likely to occur at line 100. If any operator in resource_requirements has a None value for a resource (which ExecutionResources uses to represent unconstrained or unset fields), the division getattr(resource_requirements[op], resource_name) / rates[op] will fail. Consider handling None values in the sum calculation as well, for example by using (getattr(...) or 0). Additionally, for better efficiency, the resource_limit is not None check could be performed before the sum calculation (lines 99-102) to avoid unnecessary computation for unconstrained resources.

[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

^{Reviewed by Cursor Bugbot for commit 00f0a40. Configure here.}

[cursor]

None guard is ineffective due to property coercion

High Severity

The resource_limit is not None guard never triggers because getattr(resource_limits, resource_name) calls the cpu/gpu/memory properties on ExecutionResources, which coerce None to 0.0 via self._cpu or 0.0. So resource_limit is always a float, never None. When a resource is truly unconstrained (_cpu is None), the property returns 0.0, and 0.0 / positive_cost yields 0.0, incorrectly capping max_throughput to zero. The fix needs to check the private _cpu/_gpu/_memory attributes or otherwise detect the unconstrained case.

 

^{Reviewed by Cursor Bugbot for commit 00f0a40. Configure here.}