fix(langchain): support Windows graph paths

[mikemikimike]

Summary

• allow Windows drive-letter paths in langgraph_wrapper graph references
• keep rejecting references with a missing module path, separator, or graph name
• extract parsing into a unit-testable helper and cover POSIX, Windows, relative, and invalid forms

Validation

• python -m pytest packages/nvidia_nat_langchain/tests/test_langgraph_workflow.py -q (26 passed)
• ruff check packages/nvidia_nat_langchain/src/nat/plugins/langchain/langgraph_workflow.py packages/nvidia_nat_langchain/tests/test_langgraph_workflow.py
• python -m compileall -q packages/nvidia_nat_langchain/src/nat/plugins/langchain/langgraph_workflow.py packages/nvidia_nat_langchain/tests/test_langgraph_workflow.py
• git diff --check

Closes #2185

Summary by CodeRabbit

• Bug Fixes

  • Improved LangGraph reference parsing to support module paths containing additional colons, including Windows-style paths.
  • Added validation to reject references with missing module paths or graph names.

• Tests

  • Added coverage for Unix-style, Windows-style, and relative module paths, plus invalid references.

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[coderabbitai]

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📥 Commits

Reviewing files that changed from the base of the PR and between 423397b and dc6c806.

📒 Files selected for processing (1)

• packages/nvidia_nat_langchain/src/nat/plugins/langchain/langgraph_workflow.py

🚧 Files skipped from review as they are similar to previous changes (1)

• packages/nvidia_nat_langchain/src/nat/plugins/langchain/langgraph_workflow.py

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Walkthrough

The graph reference parser now splits at the final colon, supports Windows drive-letter paths, rejects missing components, and is covered by focused parameterized tests.

Changes

Graph path parsing

Layer / File(s)	Summary
Path parser and registration integration packages/nvidia_nat_langchain/src/nat/plugins/langchain/langgraph_workflow.py, packages/nvidia_nat_langchain/tests/test_langgraph_workflow.py	Adds split_graph_path for final-colon parsing and validation. Updates register to use it. Tests Unix, Windows, relative, and invalid graph references.

Estimated code review effort: 2 (Simple) | ~10 minutes

Merge Risk: ⚪ Minimal · up to dc6c8

The change adds support for Windows graph paths while preserving rejection of invalid references; no actionable merge-blocking risk remains after normal checks and review.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title is concise, descriptive, and uses imperative mood. It accurately identifies the LangChain fix for Windows graph paths.
Linked Issues check	✅ Passed	The changes satisfy issue [#2185] by splitting graph references at the final colon, supporting Windows drive-letter paths, preserving POSIX and relative paths, and rejecting missing separators or empt…
Out of Scope Changes check	✅ Passed	All changes are directly related to issue [#2185]. The source change updates graph-path parsing, and the tests provide regression coverage for the required path formats and validation rules.
Docstring Coverage	✅ Passed	Docstring coverage is 80.00% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 5 functions across 2 files.

Full details: Linked Issues check

Explanation

The changes satisfy issue [#2185] by splitting graph references at the final colon, supporting Windows drive-letter paths, preserving POSIX and relative paths, and rejecting missing separators or empty module and graph names. Direct unit tests cover the required valid and invalid cases.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[willkill07]

/ok to test 423397b

[willkill07]

@mikemikimike pre-commit is failing

[mikemikimike]

/ok to test dc6c806

[mikemikimike]

Fixed the pre-commit failure by applying the yapf-required formatting to the ValueError in split_graph_path. Verified locally with 26 focused tests, ruff, compileall, yapf 0.43.0, and git diff --check. The NVIDIA CI workflow still requires maintainer approval to run on this fork.