Whitelist argparse and getopt as safe modules

[crowcreation]

Summary

Move argparse and getopt from DANGEROUS_MODULES to SAFE_MODULES in the Python handler. Both are pure argv-parsing stdlib modules whose only side effects are stdout/stderr text and sys.exit on bad args — none of which is in the analyser's threat model:

• print is already whitelisted, so --help/error text to stdout/stderr is consistent with existing policy.
• sys.exit just terminates the script — not code execution, file I/O, or network access.
• Neither module can read/write files, open sockets, spawn processes, or touch the filesystem.

Motivation

Nearly every real-world CLI script imports argparse. Listing it as dangerous caused the static analyser to ask for approval on essentially every script the handler sees — defeating the handler's purpose of auto-approving provably safe code. I hit this constantly with my own CLI tooling under scripts/, which prompted a dig through python.py.

What is deliberately NOT changed

• logging — real FileHandler/SocketHandler/SMTPHandler exist
• sys — sys.modules manipulation, sys.stdin/sys.stdout usable as file objects
• getpass — reads from tty (I/O)
• atexit — enables deferred execution of unreviewed handlers

These retain defensible I/O or exec vectors and stay in DANGEROUS_MODULES.

Test plan

• Added test_safe_script_argparse_approved and test_safe_script_getopt_approved in TestPythonScriptAnalysis, mirroring existing safe-import test style.
• Full tests/cli/test_python.py suite (127 tests) passes on Python 3.14 via uv run.
• Existing dangerous-import tests (os, subprocess, pathlib, socket, requests, etc.) unaffected.

[ldayton]

Thanks for this — and the careful writeup. getopt is clean (pure string matching, no I/O), so that half is good to go.

argparse is trickier than "pure argv parsing", though: it has built-in file access that happens inside the library, so the script's AST looks innocent and the analyzer can't see it. A few that auto-approve once argparse is safe:

• type=argparse.FileType('w'/'a') — opens/truncates a file
• type=argparse.FileType('r') — reads any file
• ArgumentParser(fromfile_prefix_chars='@') — reads a file named by an @path arg
• type=eval — argparse calls eval(arg) at runtime (RCE)

The first three are the real issue: whitelisting argparse means an argparse script can no longer be proven safe by static analysis, which is the bar the handler sets ("if we can't prove it's safe, ask"). (type=eval is actually a separate, pre-existing gap — list(map(eval, data)) already analyzes as safe today with no argparse involved.)

Suggestion: land getopt as-is, and for argparse add targeted guards so the common case still auto-approves but FileType / fromfile_prefix_chars flag as dangerous. Happy to help wire that up if you'd like.