[Store] Fix with_hard_pin failure in python API

[0oshowero0]

Description

While PR #1728 introduced the with_hard_pin capability to the C++ core, the corresponding Python interface was missing.

Currently, attempting to configure with_hard_pin via the Python API results in the following error:

from mooncake.store import ReplicateConfig
config = ReplicateConfig()
config.with_hard_pin = True

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'mooncake.store.ReplicateConfig' object has no attribute 'with_hard_pin'

Root Cause & Solution:

The with_hard_pin attribute was not registered in the pybind11 module (store_py.cpp). This PR fixes the issue by explicitly exposing with_hard_pin via pybind11, aligning the Python API with the underlying C++ ReplicateConfig struct.

Module

• Transfer Engine (mooncake-transfer-engine)
• Mooncake Store (mooncake-store)
• Mooncake EP (mooncake-ep)
• Integration (mooncake-integration)
• P2P Store (mooncake-p2p-store)
• Python Wheel (mooncake-wheel)
• PyTorch Backend (mooncake-pg)
• Mooncake RL (mooncake-rl)
• CI/CD
• Docs
• Other

Type of Change

• Bug fix
• New feature
• Refactor
• Breaking change
• Documentation update
• Other

How Has This Been Tested?

Checklist

• I have performed a self-review of my own code.
• I have formatted my own code using ./scripts/code_format.sh before submitting.
• I have updated the documentation.
• I have added tests to prove my changes are effective.

[Copilot]

Pull request overview

This PR aligns the Mooncake Store client-facing APIs with the C++ core’s ReplicateConfig.with_hard_pin capability by exposing the flag in bindings.

Changes:

• Expose ReplicateConfig.with_hard_pin in the Python pybind11 module.
• Extend the C API replicate config (mooncake_replicate_config_t) and map it into the C++ ReplicateConfig.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
mooncake-store/src/store_c.cpp	Maps the C replicate config into the C++ ReplicateConfig, including with_hard_pin.
mooncake-store/include/store_c.h	Adds with_hard_pin to the public C API replicate config struct.
mooncake-integration/store/store_py.cpp	Exposes with_hard_pin to Python via pybind11.

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[Copilot]

Adding with_hard_pin into mooncake_replicate_config changes the struct layout/size for the public C API. Existing callers compiled against the old header will pass a smaller/differently-laid-out struct, and the library will misinterpret preferred_segments as with_hard_pin (and shift the remaining fields), which can cause UB or unintended hard-pinning. Consider introducing a versioned config struct (e.g., mooncake_replicate_config_v2 + new entrypoints) or adding an explicit struct_size/version field so the callee can detect whether with_hard_pin is present; also update downstream language bindings that construct this struct by field name (e.g., the Rust wrapper currently uses a struct literal).

[Copilot]

to_replicate_config() now unconditionally reads c_config->with_hard_pin. With the current C API change, any caller compiled against an older store_c.h (without the new field / different layout) can trigger incorrect reads (e.g., interpreting preferred_segments as the flag) and potentially crash or silently enable hard pinning. If backward compatibility is required, the C API needs a way to communicate the config struct version/size before this field is read.

[Copilot]

The new Python-exposed with_hard_pin flag should be covered by the existing Python wheel tests that validate ReplicateConfig property access (e.g., default value and assignment), otherwise this regression can reappear unnoticed.

[gemini-code-assist]

Code Review

This pull request introduces a new configuration option "with_hard_pin" to the ReplicateConfig structure. The changes include updating the C header definition, the conversion logic in the C++ implementation, and exposing the field via Python bindings. I have no feedback to provide.

[codecov-commenter]

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Codecov Report

❌ Patch coverage is 0% with 2 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
mooncake-integration/store/store_py.cpp	0.00%	1 Missing ⚠️
mooncake-store/src/store_c.cpp	0.00%	1 Missing ⚠️

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[stmatengss]

LGTM