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Type annotation gaps and unhandled FileNotFoundError in src/mcp/cli/cli.py

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  • #3687 by @Sak3th2004 — closed without merging

Assessment

Difficulty
2/5
Estimated time
1-3 hours
Newbie friendliness
84/100
Issue type
Bug
Clarity
Clearly specified
Activity status
Active
Tech stack
python
Domain
cli

Research direction

Read src/mcp/cli/cli.py, focusing on _get_npx_command, _import_server, and _check_server_object. Check how the Windows npx probe handles a missing executable, then run the relevant CLI tests and the stated Ruff and Pyright checks. Done when the exception is handled and the requested annotations pass those checks.

Written by the indexing model from the issue text.

Description

enhancement
Environment / Context

While running static analysis (ruff check --select ANN and pyright) on src/mcp/cli/cli.py during local development, I noticed a few missing type annotations and an uncaught exception edge case on Windows.

Description

  1. Unhandled FileNotFoundError in _get_npx_command:
    In src/mcp/cli/cli.py, _get_npx_command() attempts to probe for npx executables on Windows inside a try...except subprocess.CalledProcessError: block. If npx.cmd or npx.exe is missing from the system entirely, subprocess.run raises FileNotFoundError before CalledProcessError can be raised, causing an unexpected crash instead of returning None.

  2. Missing Return Type Annotations (ANN202):

    • _get_npx_command() lacks a return type annotation (returns str | None).
    • _import_server() lacks a return type annotation.
    • _check_server_object() lacks a return type annotation (-> bool).

  3. Any Type Usage (ANN401):

    • _check_server_object() uses server_object: Any, which can be tightened to object since it performs runtime isinstance checks.
Proposed Fix
  • Update _get_npx_command() to catch (subprocess.CalledProcessError, FileNotFoundError) and return str | None.
  • Add explicit return type annotations to _import_server and _check_server_object.
  • Replace server_object: Any with server_object: object.

I would be happy to submit a PR for this if a maintainer is willing to assign the issue to me!
I know that the contributing guidelines for this project forbid direct PRs about formatting and such without assigning, so just putting this out there.

(Note: Disclosing per guidelines that AI tools were used to assist in local testing and analysis; I am ready to own, test, and answer questions on the proposed changes).

Dominant language
Python
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Forks
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Avg merge
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Merged PRs (30d)
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