Add Race, All, Take, Debounce saga effects and gateway tests (#29)

* Add Race, All, Take, Debounce saga effects, fix pipeline bug, add gateway tests (#29)

Expand saga effects from 8 to 12 with Race (first-wins), All (wait-all),
Take (action-waiting), and Debounce (timer-restart). Fix Python 2 exception
syntax in pipeline.py:401. Add 28 gateway tests (previously 0 coverage).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* Fix CI: ruff format, revert pipeline.py to valid 3.14 syntax, add changelog fragment

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* Fix flaky debounce test: increase sleep margins for CI

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* Fix Race effect TOCTOU race on free-threaded Python

On Python 3.14t (no GIL), a child saga could finish between the
per-child done.is_set() for-loop and the all-done check, causing
_execute_race to hit the fallback `return None` path instead of
returning the child's result. Re-check results in the all-done branch.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* Address PR review: Take cancel-awareness, waiter cleanup, composable child sagas

- Take effect now polls in short intervals (0.1s) so saga cancellation
  can interrupt even indefinite waits, instead of blocking on a single
  waiter_event.wait() call.
- Take waiter cleanup now deletes the dict key when the per-action list
  becomes empty, preventing unbounded growth of _action_waiters.
- Replaced duplicated effect-stepping logic in _run_saga_capturing with
  a yield-from wrapper that delegates to _run_saga, making child sagas
  in Race/All fully composable with all effect types (Take, Debounce,
  nested Race/All, etc.).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: lbliii

changelog.d/+saga-effects-expansion.added.md

@@ -0,0 +1 @@
+Added Race (first-wins with loser cancellation), All (wait-all with fail-fast), Take (pause until action dispatched), and Debounce (cancel-and-restart timer) saga effects. Fixed Python 2 exception syntax bug in pipeline handler introspection. Added gateway test suite covering namespacing, routing, proxying, idle reaping, and error handling.

src/milo/__init__.py

@@ -28,6 +28,10 @@ def __getattr__(name: str):
         "Retry": "_types",
         "Timeout": "_types",
         "TryCall": "_types",
+        "Race": "_types",
+        "All": "_types",
+        "Take": "_types",
+        "Debounce": "_types",
         "Cmd": "_types",
         "Batch": "_types",
         "Sequence": "_types",
@@ -154,6 +158,7 @@ def _Py_mod_gil() -> int:  # noqa: N802
     "CLI",
     "DEFAULT_THEME",
     "Action",
+    "All",
     "App",
     "AppError",
     "AppStatus",
@@ -168,6 +173,7 @@ def _Py_mod_gil() -> int:  # noqa: N802
     "ConfigSpec",
     "Context",
     "CycleError",
+    "Debounce",
     "Delay",
     "Description",
     "DevServer",
@@ -213,6 +219,7 @@ def _Py_mod_gil() -> int:  # noqa: N802
     "PromptDef",
     "Put",
     "Quit",
+    "Race",
     "ReducerResult",
     "RenderTarget",
     "RequestLog",
@@ -225,6 +232,7 @@ def _Py_mod_gil() -> int:  # noqa: N802
     "SpecialKey",
     "StateError",
     "Store",
+    "Take",
     "ThemeProxy",
     "ThemeStyle",
     "TickCmd",

src/milo/_types.py

@@ -269,6 +269,78 @@ class TryCall:
     kwargs: dict = field(default_factory=dict)
 
 
+@dataclass(frozen=True, slots=True)
+class Race:
+    """Run multiple sagas concurrently, return the first result.
+
+    Losers are cancelled via their cancel events as soon as a winner
+    completes.  If all racers fail, the first error is thrown into
+    the parent saga::
+
+        winner = yield Race(sagas=(fetch_primary(), fetch_fallback()))
+
+    Raises ``StateError`` if *sagas* is empty.
+    """
+
+    sagas: tuple
+
+
+@dataclass(frozen=True, slots=True)
+class All:
+    """Run multiple sagas concurrently, wait for all to complete.
+
+    Returns a tuple of results in the same order as the input sagas.
+    Fail-fast: if any saga raises, remaining sagas are cancelled and
+    the error is thrown into the parent::
+
+        a, b = yield All(sagas=(fetch_users(), fetch_roles()))
+
+    An empty tuple returns ``()`` immediately.
+    """
+
+    sagas: tuple
+
+
+@dataclass(frozen=True, slots=True)
+class Take:
+    """Pause the saga until a matching action is dispatched.
+
+    Waits for *future* actions only — actions dispatched before the
+    Take is yielded are not matched.  Returns the full ``Action``
+    object so the saga can inspect both type and payload::
+
+        action = yield Take("USER_CONFIRMED")
+        name = action.payload["name"]
+
+    An optional *timeout* (in seconds) raises ``TimeoutError`` if the
+    action is not dispatched in time.
+    """
+
+    action_type: str
+    timeout: float | None = None
+
+
+@dataclass(frozen=True, slots=True)
+class Debounce:
+    """Delay-then-fork: start a timer, fork *saga* when it expires.
+
+    If the parent saga yields another ``Debounce`` before the timer
+    fires, the previous timer is cancelled and restarted.  The parent
+    continues immediately (non-blocking)::
+
+        # In a keystroke handler saga:
+        while True:
+            key = yield Take("@@KEY")
+            yield Debounce(seconds=0.3, saga=search_saga)
+
+    The debounced saga runs independently; use ``Take`` if the parent
+    needs the result.
+    """
+
+    seconds: float
+    saga: Callable
+
+
 # ---------------------------------------------------------------------------
 # Commands (lightweight alternative to sagas)
 # ---------------------------------------------------------------------------