RAHHH

backend/lib/python3.12/site-packages/twisted/trial/_dist/functional.py

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+# Copyright (c) Twisted Matrix Laboratories.
+# See LICENSE for details.
+
+"""
+General functional-style helpers for disttrial.
+"""
+
+from functools import partial, wraps
+from typing import Awaitable, Callable, Iterable, Optional, TypeVar
+
+from twisted.internet.defer import Deferred, succeed
+
+_A = TypeVar("_A")
+_B = TypeVar("_B")
+_C = TypeVar("_C")
+
+
+def fromOptional(default: _A, optional: Optional[_A]) -> _A:
+    """
+    Get a definite value from an optional value.
+
+    @param default: The value to return if the optional value is missing.
+
+    @param optional: The optional value to return if it exists.
+    """
+    if optional is None:
+        return default
+    return optional
+
+
+def takeWhile(condition: Callable[[_A], bool], xs: Iterable[_A]) -> Iterable[_A]:
+    """
+    :return: An iterable over C{xs} that stops when C{condition} returns
+        ``False`` based on the value of iterated C{xs}.
+    """
+    for x in xs:
+        if condition(x):
+            yield x
+        else:
+            break
+
+
+async def sequence(a: Awaitable[_A], b: Awaitable[_B]) -> _B:
+    """
+    Wait for one action to complete and then another.
+
+    If either action fails, failure is propagated.  If the first action fails,
+    the second action is not waited on.
+    """
+    await a
+    return await b
+
+
+def flip(f: Callable[[_A, _B], _C]) -> Callable[[_B, _A], _C]:
+    """
+    Create a function like another but with the order of the first two
+    arguments flipped.
+    """
+
+    @wraps(f)
+    def g(b, a):
+        return f(a, b)
+
+    return g
+
+
+def compose(fx: Callable[[_B], _C], fy: Callable[[_A], _B]) -> Callable[[_A], _C]:
+    """
+    Create a function that calls one function with an argument and then
+    another function with the result of the first function.
+    """
+
+    @wraps(fx)
+    @wraps(fy)
+    def g(a):
+        return fx(fy(a))
+
+    return g
+
+
+# Discard the result of an awaitable and substitute None in its place.
+discardResult: Callable[[Awaitable[_A]], Deferred[None]] = compose(
+    Deferred.fromCoroutine,
+    partial(flip(sequence), succeed(None)),
+)
+
+
+async def iterateWhile(
+    predicate: Callable[[_A], bool],
+    action: Callable[[], Awaitable[_A]],
+) -> _A:
+    """
+    Call a function repeatedly until its result fails to satisfy a predicate.
+
+    @param predicate: The check to apply.
+
+    @param action: The function to call.
+
+    @return: The result of C{action} which did not satisfy C{predicate}.
+    """
+    while True:
+        result = await action()
+        if not predicate(result):
+            return result
+
+
+def countingCalls(f: Callable[[int], _A]) -> Callable[[], _A]:
+    """
+    Wrap a function with another that automatically passes an integer counter
+    of the number of calls that have gone through the wrapper.
+    """
+    counter = 0
+
+    def g() -> _A:
+        nonlocal counter
+        try:
+            result = f(counter)
+        finally:
+            counter += 1
+        return result
+
+    return g