Flatten the implementation of the pipeline() decorator.

It seems easier to follow in a single function rather than being spread
out in multiple helpers.  (It also makes the signature of `pipeline()`
explicit without having to duplicate it.)

Author: anntzer

slicerator/__init__.py

@@ -3,7 +3,7 @@
 
 import collections.abc
 import itertools
-from functools import wraps
+from functools import partial, wraps
 from copy import copy
 import inspect
 
@@ -503,7 +503,7 @@ def __setstate__(self, data_as_list):
         return self.__init__(lambda x: x, data_as_list)
 
 
-def pipeline(func=None, **kwargs):
+def pipeline(func=None, *, retain_doc=False, ancestor_count=1):
     """Decorator to enable lazy evaluation of a function.
 
     When the function is applied to a Slicerator or Pipeline object, it
@@ -540,8 +540,8 @@ def pipeline(func=None, **kwargs):
     Apply the pipeline decorator to your image processing function.
 
     >>> @pipeline
-    ...  def color_channel(image, channel):
-    ...      return image[channel, :, :]
+    ... def color_channel(image, channel):
+    ...     return image[channel, :, :]
     ...
 
 
@@ -583,94 +583,19 @@ def pipeline(func=None, **kwargs):
     ...  def sum_offset(img1, img2, offset):
     ...      return img1 + img2 + offset
     """
-    def wrapper(f):
-        return _pipeline(f, **kwargs)
-
     if func is None:
-        return wrapper
-    else:
-        return wrapper(func)
+        return partial(
+            pipeline, retain_doc=retain_doc, ancestor_count=ancestor_count)
 
+    if ancestor_count == 'all':
+        ancestor_count = len(
+            p for p in inspect.signature(func).parameters
+            if p.kind.name in ["POSITIONAL_ONLY", "POSITIONAL_OR_KEYWORD"])
 
-def _pipeline(func_or_class, **kwargs):
     try:
-        is_class = issubclass(func_or_class, Pipeline)
+        is_class = issubclass(func, Pipeline)
     except TypeError:
         is_class = False
-    if is_class:
-        return _pipeline_fromclass(func_or_class, **kwargs)
-    else:
-        return _pipeline_fromfunc(func_or_class, **kwargs)
-
-
-def _pipeline_fromclass(cls, retain_doc=False, ancestor_count=1):
-    """Actual `pipeline` implementation
-
-    Parameters
-    ----------
-    func : class
-        Class for lazy evaluation
-    retain_doc : bool
-        If True, don't modify `func`'s doc string to say that it has been
-        made lazy
-    ancestor_count : int or 'all', optional
-        Number of inputs to the pipeline. Defaults to 1.
-
-    Returns
-    -------
-    Pipeline
-        Lazy function evaluation :py:class:`Pipeline` for `func`.
-    """
-    if ancestor_count == 'all':
-        # subtract 1 for `self`
-        ancestor_count = len(inspect.getfullargspec(cls).args) - 1
-
-    @wraps(cls)
-    def process(*args, **kwargs):
-        ancestors = args[:ancestor_count]
-        args = args[ancestor_count:]
-        all_pipe = all(hasattr(a, '_slicerator_flag') or
-                       isinstance(a, Slicerator) or
-                       isinstance(a, Pipeline) for a in ancestors)
-        if all_pipe:
-            return cls(*(ancestors + args), **kwargs)
-        else:
-            # Fall back on normal behavior of func, interpreting input
-            # as a single image.
-            return cls(*(tuple([a] for a in ancestors) + args), **kwargs)[0]
-
-    if not retain_doc:
-        if process.__doc__ is None:
-            process.__doc__ = ''
-        process.__doc__ = ("This function has been made lazy. When passed\n"
-                           "a Slicerator, it will return a \n"
-                           "Pipeline of the results. When passed \n"
-                           "any other objects, its behavior is "
-                           "unchanged.\n\n") + process.__doc__
-    process.__name__ = cls.__name__
-    return process
-
-
-def _pipeline_fromfunc(func, retain_doc=False, ancestor_count=1):
-    """Actual `pipeline` implementation
-
-    Parameters
-    ----------
-    func : callable
-        Function for lazy evaluation
-    retain_doc : bool
-        If True, don't modify `func`'s doc string to say that it has been
-        made lazy
-    ancestor_count : int or 'all', optional
-        Number of inputs to the pipeline. Defaults to 1.
-
-    Returns
-    -------
-    Pipeline
-        Lazy function evaluation :py:class:`Pipeline` for `func`.
-    """
-    if ancestor_count == 'all':
-        ancestor_count = len(inspect.getfullargspec(func).args)
 
     @wraps(func)
     def process(*args, **kwargs):
@@ -679,24 +604,28 @@ def process(*args, **kwargs):
         all_pipe = all(hasattr(a, '_slicerator_flag') or
                        isinstance(a, Slicerator) or
                        isinstance(a, Pipeline) for a in ancestors)
-        if all_pipe:
-            def proc_func(*x):
-                return func(*(x + args), **kwargs)
 
-            return Pipeline(proc_func, *ancestors)
+        if is_class:
+            return (func(*ancestors, *args, **kwargs)
+                    if all_pipe else
+                    # Fall back on normal behavior of func, interpreting input
+                    # as a single image.
+                    func(*[[a] for a in ancestors], *args, **kwargs)[0])
+
         else:
-            # Fall back on normal behavior of func, interpreting input
-            # as a single image.
-            return func(*(ancestors + args), **kwargs)
+            return (Pipeline(lambda *x: func(*x, *args, **kwargs), *ancestors)
+                    if all_pipe else
+                    # Fall back on normal behavior of func, interpreting input
+                    # as a single image.
+                    func(*ancestors, *args, **kwargs))
 
     if not retain_doc:
         if process.__doc__ is None:
             process.__doc__ = ''
-        process.__doc__ = ("This function has been made lazy. When passed\n"
-                           "a Slicerator, it will return a \n"
-                           "Pipeline of the results. When passed \n"
-                           "any other objects, its behavior is "
-                           "unchanged.\n\n") + process.__doc__
+        process.__doc__ = (
+            "This function has been made lazy. When passed a Slicerator, it \n"
+            "will return a Pipeline of the results. When passed any other \n"
+            "objects, its behavior is unchanged.\n\n" + process.__doc__)
     process.__name__ = func.__name__
     return process