Add returns_result and unwrap_or_return to emulate question mark operator

Author: olekli

src/result/__init__.py

@@ -6,6 +6,7 @@
     UnwrapError,
     as_async_result,
     as_result,
+    returns_result,
     is_ok,
     is_err,
     do,
@@ -20,6 +21,7 @@
     "UnwrapError",
     "as_async_result",
     "as_result",
+    "returns_result",
     "is_ok",
     "is_err",
     "do",

src/result/result.py

@@ -146,6 +146,12 @@ def unwrap_or_raise(self, e: object) -> T:
         """
         return self._value
 
+    def unwrap_or_return(self) -> T:
+        """
+        Return the value.
+        """
+        return self._value
+
     def map(self, op: Callable[[T], U]) -> Ok[U]:
         """
         The contained result is `Ok`, so return `Ok` with original value mapped to
@@ -358,6 +364,12 @@ def unwrap_or_raise(self, e: Type[TBE]) -> NoReturn:
         """
         raise e(self._value)
 
+    def unwrap_or_return(self) -> NoReturn:
+        """
+        The contained result is ``Err``, raise DoException with self.
+        """
+        raise DoException(self)
+
     def map(self, op: object) -> Err[E]:
         """
         Return `Err` with the same value
@@ -464,6 +476,24 @@ def result(self) -> Result[Any, Any]:
         return self._result
 
 
+def returns_result() -> Callable[[Callable[P, Result[R, E]]], Callable[P, Result[R, E]]]:
+    """
+    Make a decorator to turn a function into one that allows using unwrap_or_return.
+    """
+    def decorator(f: Callable[P, Result[R, E]]) -> Callable[P, Result[R, E]]:
+        @functools.wraps(f)
+        def wrapper(*args: P.args, **kwargs: P.kwargs) -> Result[R, E]:
+            try:
+                return f(*args, **kwargs)
+            except DoException as e:
+                out: Err[E] = e.err  # type: ignore
+                return out
+
+        return wrapper
+
+    return decorator
+
+
 def as_result(
     *exceptions: Type[TBE],
 ) -> Callable[[Callable[P, R]], Callable[P, Result[R, TBE]]]:

tests/test_result.py

@@ -4,7 +4,7 @@
 
 import pytest
 
-from result import Err, Ok, OkErr, Result, UnwrapError, as_async_result, as_result
+from result import Err, Ok, OkErr, Result, UnwrapError, as_async_result, as_result, returns_result
 
 
 def test_ok_factories() -> None:
@@ -158,6 +158,22 @@ def test_unwrap_or_raise() -> None:
     assert exc_info.value.args == ('nay',)
 
 
+def test_unwrap_or_return() -> None:
+    @returns_result()
+    def func(yay):
+        if yay:
+            o = Ok('yay')
+            value = o.unwrap_or_return()
+            return Ok(value)
+        else:
+            n = Err('nay')
+            value = n.unwrap_or_return()
+            assert False
+
+    assert func(True).ok() == 'yay'
+    assert func(False).err() == 'nay'
+
+
 def test_map() -> None:
     o = Ok('yay')
     n = Err('nay')