Fixes

- Type callback protocols
- Add missing exports

Author: dbrattli

README.md

@@ -72,6 +72,7 @@ $ pip3 install expression
 4. [Optional Values](https://github.com/cognitedata/Expression/blob/main/notebooks/04%20-%20Optional%20Values.md)
 5. [Railway Oriented Programming](https://github.com/cognitedata/Expression/blob/main/notebooks/05%20-%20Railway%20Oriented%20Programming.md)
 6. [Effects and Side-effects](https://github.com/cognitedata/Expression/blob/main/notebooks/06%20-%20Effects%20and%20Side-Effects.md)
+
 ## Goals
 
 - Industrial strength library for functional programming in Python.

expression/collections/frozenlist.py

@@ -20,8 +20,21 @@
 
 import builtins
 import functools
-from typing import (Any, Callable, Generic, Iterable, Iterator, List, Optional,
-                    Protocol, Tuple, TypeVar, cast, get_origin, overload)
+from typing import (
+    Any,
+    Callable,
+    Generic,
+    Iterable,
+    Iterator,
+    List,
+    Optional,
+    Protocol,
+    Tuple,
+    TypeVar,
+    cast,
+    get_origin,
+    overload,
+)
 
 from expression.core import Case, Nothing, Option, Some, pipe
 
@@ -426,6 +439,13 @@ def __call__(self, __source: FrozenList[TSource]) -> FrozenList[TSource]:
         ...
 
 
+class TransformFn(Protocol[TResult]):
+    """A partially applied filter function."""
+
+    def __call__(self, __source: FrozenList[TSource]) -> FrozenList[TResult]:
+        ...
+
+
 def append(source: FrozenList[TSource]) -> Callable[[FrozenList[TSource]], FrozenList[TSource]]:
     def _append(other: FrozenList[TSource]) -> FrozenList[TSource]:
         return source.append(other)
@@ -586,7 +606,7 @@ def is_empty(source: FrozenList[TSource]) -> bool:
     return source.is_empty()
 
 
-def map(mapper: Callable[[TSource], TResult]) -> Callable[[FrozenList[TSource]], FrozenList[TResult]]:
+def map(mapper: Callable[[TSource], TResult]) -> TransformFn[TResult]:
     """Map list.
 
     Builds a new collection whose elements are the results of applying

expression/collections/seq.py

@@ -19,8 +19,7 @@
 import builtins
 import functools
 import itertools
-from typing import (Any, Callable, Iterable, Iterator, Optional, Protocol,
-                    Tuple, TypeVar, overload)
+from typing import Any, Callable, Iterable, Iterator, Optional, Protocol, Tuple, TypeVar, overload
 
 from expression.core import Case, Option, SupportsLessThan, identity, pipe
 
@@ -290,7 +289,7 @@ def concat(*iterables: Iterable[TSource]) -> Iterable[TSource]:
 """The empty sequence."""
 
 
-def filter(predicate: Callable[[TSource], bool]) -> Callable[[Iterable[TSource]], Iterable[TSource]]:
+def filter(predicate: Callable[[TSource], bool]) -> FilterFn:
     """Filter sequence.
 
     Filters the sequence to a new sequence containing only the
@@ -450,7 +449,7 @@ def _iter(source: Iterable[TSource]) -> None:
     return _iter
 
 
-def map(mapper: Callable[[TSource], TResult]) -> Callable[[Iterable[TSource]], Iterable[TResult]]:
+def map(mapper: Callable[[TSource], TResult]) -> TransformFn[TResult]:
     """Map source sequence.
 
     Builds a new collection whose elements are the results of
@@ -692,7 +691,10 @@ def _zip(source2: Iterable[TResult]) -> Iterable[Tuple[TSource, TResult]]:
     "of",
     "of_list",
     "of_iterable",
+    "range",
     "scan",
     "singleton",
+    "take",
     "unfold",
+    "zip",
 ]

expression/core/builder.py

@@ -92,3 +92,6 @@ def wrapper(*args: Any, **kw: Any) -> TOuter:
             return result
 
         return wrapper
+
+
+__all__ = ["Builder"]

expression/core/choice.py

@@ -144,3 +144,15 @@ def __init__(self, value: C) -> None:
     def case(cls, case: Case[C]) -> Iterable[C]:
         """Helper to cast the match result to correct type."""
         return case(cls)
+
+
+__all__ = [
+    "Choice",
+    "Choice2",
+    "Choice3",
+    "Choice1of2",
+    "Choice2of2",
+    "Choice1of3",
+    "Choice2of3",
+    "Choice3of3",
+]

expression/core/error.py

@@ -18,7 +18,8 @@ def __init__(self, expr: Any):
 
 
 def failwith(message: str) -> NoReturn:
+    """Raise exception with the given message string."""
     raise Exception(message)
 
 
-__all__ = ["EffectError", "failwith"]
+__all__ = ["EffectError", "failwith", "MatchFailureError"]

expression/core/option.py

@@ -14,6 +14,7 @@
     Iterator,
     List,
     Optional,
+    Protocol,
     TypeVar,
     Union,
     cast,
@@ -317,6 +318,7 @@ def __iter__(self) -> Iterator[TSource]:
         We basically want to return nothing, but we have to return
         something to signal fail.
         """
+
         raise Nothing
         while False:
             yield
@@ -333,6 +335,16 @@ def __str__(self):
         return "Nothing"
 
 
+class TransformFn(Protocol[TResult]):
+    """Option transforming protocol function.
+
+    `Option[TSource]) -> Option[TResult]`
+    """
+
+    def __call__(self, __source: Option[TSource]) -> Option[TResult]:
+        raise NotImplementedError
+
+
 # The singleton None class. We use the name 'Nothing' here instead of `None` to
 # avoid conflicts with the builtin `None` value in Python.
 # Note to self: Must be of type `Nothing_` or pattern matching will not work.
@@ -345,7 +357,7 @@ def __str__(self):
 """
 
 
-def bind(mapper: Callable[[TSource], Option[TResult]]) -> Callable[[Option[TSource]], Option[TResult]]:
+def bind(mapper: Callable[[TSource], Option[TResult]]) -> TransformFn[TResult]:
     """Bind option.
 
     Applies and returns the result of the mapper if the value is
@@ -386,7 +398,7 @@ def is_some(option: Option[TSource]) -> bool:
     return option.is_some()
 
 
-def map(mapper: Callable[[TSource], TResult]) -> Callable[[Option[TSource]], Option[TResult]]:
+def map(mapper: Callable[[TSource], TResult]) -> TransformFn[TResult]:
     def _map(option: Option[TSource]) -> Option[TResult]:
         return option.map(mapper)
 

expression/core/result.py

@@ -251,22 +251,20 @@ def __str__(self):
         return f"Error {self._error}"
 
 
-class TransformFn(Protocol[TSource, TResult]):
+class TransformFn(Protocol[TResult]):
     def __call__(self, __source: Result[TSource, TError]) -> Result[TResult, TError]:
         ...
 
 
-def map(mapper: Callable[[TSource], TResult]) -> TransformFn[TSource, TResult]:
+def map(mapper: Callable[[TSource], TResult]) -> TransformFn[TResult]:
     def _map(result: Result[TSource, TError]) -> Result[TResult, TError]:
         return result.map(mapper)
 
     # return cast(TransformFn[TSource, TResult], _map)  # NOTE: cast for mypy
     return _map
 
 
-def bind(
-    mapper: Callable[[TSource], Result[TResult, TError]]
-) -> Callable[[Result[TSource, TError]], Result[TResult, TError]]:
+def bind(mapper: Callable[[TSource], Result[TResult, TError]]) -> TransformFn[TResult]:
     def _bind(result: Result[TSource, TError]) -> Result[TResult, TError]:
         return result.bind(mapper)