[thorwhalen]

Summary

• FuncFactory can be called with anywhere from none to all of the underlying function's arguments, but its signature previously showed the required-looking params (no default) as if they were mandatory to call the factory itself, which they aren't.
• Activates the NotSet-sentinel approach that was already sketched out (commented-out) in i2/deco.py, and prototyped 3 years ago on the unmerged branch origin/48-using-a-notset-sentinel-to-solve-make-funcfactory-instances-signature-more-truthful-about-argument-requirements ("add Thor's patch" + follow-ups by @sylvainbonnot, Jan 2023).
• Correction vs. that old branch: avoids re-indexing the signature through Sig.__getitem__ a second time (shown_factory_sig[self.include]), since that silently drops the return annotation -- a separate, pre-existing bug in Sig.__getitem__/from_params that is not addressed here (worth its own issue if relevant, related in spirit to Careful reordering when adding keyword-only params to a list that already has a variadic keyword. #17).
• Updates the two affected FuncFactory doctests and the test_rm_params regression test (rm_params with allow_removal_of_non_defaulted_params doesn't exactly work #44) to reflect the new, more truthful signature display.

Closes #48

Dependents checked

Per fleet_dependents.json, on-box packages importing FuncFactory are front, ju, slang, streamlitfront. None introspect its Sig(...) string, so this is low-risk; full local test suite (761 passed, 2 xfailed) and black --check are green.

Test plan

• pytest --doctest-modules i2/ -> 761 passed, 2 xfailed
• black --check on changed files
• Manual repro of the issue's FuncFactory example now shows (x=NotSet, y=NotSet, z=2)

🤖 Generated with Claude Code

https://claude.ai/code/session_011HSBVhDjRU4apSLcRkavv9

[thorwhalen]

Note (added after merge): this PR was self-reviewed only -- no independent sub-agent review, since it was merged before a crowsnest policy update requiring one for behaviour-changing merges. Flagging for transparency; the change itself (full local test suite: 761 passed, 2 xfailed; CI green) stands, but a second look is welcome.