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Deferred TODOs

Dispatch: indistinguishable parametric ABC multimethods (GitHub #99)

Dispatch-layer improvements for parametric ABCs — warn/error on indistinguishable multimethods. Tricky because checkability is value-dependent (Sized vs opaque iterator). Typecheck-layer part is resolved.

Type annotations — remaining hard-tier modules

As of v2.1.0, 32 of 34 pure-Python modules are annotated. Two remain — genuinely resistant to static typing:

  • dispatch.py (7 exports) — runtime multiple dispatch, typing module introspection, multimethod resolution.
  • typecheck.py (1 export) — deeply introspective runtime type checking; the function is the type system.

Also within already-annotated modules, some functions were deliberately left unannotated: curry, compose* family, flatten* family (dynamic arity, Values unpacking, recursive type flattening). Convention established: F = TypeVar('F', bound=Callable) for callables, T = TypeVar('T') for data values; fillvalue parameters use Any (sentinel may differ from element type). The original audit concern (abstract params, concrete returns, no deprecated typing forms) should be checked against the annotations added. PEP 695 TODOs left in arity.py and conditions.py for when floor bumps to 3.12.

Updated 2026-04-17.

Tier 2 REPL tests (subprocess + pty) for unpythonic.net client/server

Tier 1 coverage for unpythonic.net.client and unpythonic.net.server uses a server-in-thread + in-process client pattern (see unpythonic/net/tests/) with scripted input via a private _input seam on client._connect(..., _input=fake_input) and captured stdout/stderr via io.StringIO. Fast, single-process, no subprocess boundary needed — the server speaks TCP to 127.0.0.1 and the client loop runs in the same test process. We might never need tier 2.

Important framing: tier 1 is a protocol and plumbing test, not a terminal-UX test. The _input seam replaces the entire input() pathway before readline is ever reached, so readline's line editor, history, completer binding, and interrupt-during-input are not partially covered — they are 0% covered. A regression in readline.parse_and_bind, in the custom remote completer wiring, or in the SIGINT-during-readline path would pass tier 1 silently. Tier 2 isn't "a safety net for edge cases" — it's the only place these things get exercised at all.

A second tier would spawn the server and client as real subprocesses, with each end driven through a pseudo-terminal (pexpect / ptyprocess), to catch things tier 1 cannot reach:

  • Real GNU-readline binding behaviour on the client side — tab completion against the remote completer, history recall, multi-line input rendering.
  • Terminal escape sequences from the colorizer on both sides.
  • Signal handling — Ctrl+C from the client forwarded to the remote REPL, Ctrl+D disconnecting cleanly.
  • The ptyproxy machinery itself, end-to-end. Tier 1 stubs around the pty by running the InteractiveConsole directly against in-memory streams; tier 2 would actually exercise unpythonic.net.ptyproxy.PTYSocketProxy with a real master/slave pair.

Cost:

  • ~0.5–1 s startup per test × two processes per test (client + server) = ~1–2 s per test. Matters for suite size.
  • POSIX-only naturally. Since D9 landed (2026-04-16), unpythonic.net runs on Windows too via socket.socketpair, but tier 2 still needs real pseudo-terminals — on Windows that means ConPTY, which D9 deliberately avoided. If tier 2 ever materializes, its Windows variant is an independent design problem.
  • pexpect would become a new dev dep. Small but non-zero.

Rough shape if we ever do it:

import pexpect
server = pexpect.spawn(f"{sys.executable} -m unpythonic.net.server", ...)
server.expect(r"Listening on \S+")
client = pexpect.spawn(f"{sys.executable} -m unpythonic.net.client", ...)
client.expect(r">>> ")
client.sendline("2 + 3")
client.expect(r"5\s*\n>>> ")
client.sendcontrol("d")
client.expect(pexpect.EOF)
server.terminate()

When to actually do it: only if tier 1 coverage turns out to miss something important (a regression hits prod that tier 1 would not have caught). The in-thread server + scripted client approach already exercises most of the protocol surface; tier 2 is primarily a safety net for terminal-semantics and signal-path bugs. Until one of those bites, tier 1 is the main win.

Added 2026-04-15, alongside the tier 1 bring-up.

Flexible view variant

An older, more flexible implementation of view exists somewhere in the ancient git history, supporting more advanced slicing at the cost of worse performance. Could be resurrected as an alternative for use cases where flexibility matters more than speed. Dig through the history to find it.

Noted 2026-04-16.

Audit bare {path} interpolation for repr/raw asymmetry on Windows

Fleet-wide audit across all projects. The known failure mode (mcpyrate cacbfd2, 2026-04-15): an f-string interpolates a file path with bare {__file__}, producing raw backslashes (C:\a\b), while the other side of a comparison uses repr()/unparse() output with escaped backslashes (C:\\a\\b) — mismatch on Windows, passes on POSIX by accident. Fix is {__file__!r} so both sides speak the same dialect. The risk is NOT f-string reinterpretation (that's safe), but asymmetry when a bare-interpolated path is compared against, compiled as, or embedded into Python source. Grep hints: __file__ in f-strings; also any path value interpolated into strings that later reach compile(), eval(), ast.unparse(), assertions, or similar.

Noted 2026-04-17.

Remove unpythonic.amb.MonadicList alias (3.0.0)

As part of the monads port, MonadicList was moved to unpythonic.monads.List with a varargs constructor (List(1, 2, 3) instead of MonadicList([1, 2, 3])). A silent alias MonadicList = List is kept in unpythonic/amb.py for backward-name compatibility during the 2.x series. Remove the alias in 3.0.0 along with the accompanying TODO(3.0.0) comment at the alias site. Users must then import List directly from unpythonic.monads. Note: this is name-only compat — the constructor signature changed at 2.0.0, so existing callers of MonadicList([...]) already needed to switch to varargs or from_iterable(...) at 2.0.0.

Noted 2026-04-17.