From 464d08a4a2053c610f70fc883bf962eae1319e5f Mon Sep 17 00:00:00 2001
From: Romain Dorgueil <romain@dorgueil.net>
Date: Wed, 27 Dec 2017 14:21:50 +0100
Subject: [PATCH] Generalize tuplize decorator to cast(...) decorator.

---
 bonobo/util/__init__.py        |  3 ++-
 bonobo/util/api.py             |  4 ++-
 bonobo/util/collections.py     | 47 +++++++++++++++++++---------------
 bonobo/util/resolvers.py       |  4 +--
 tests/util/test_collections.py | 11 +++++---
 5 files changed, 40 insertions(+), 29 deletions(-)

diff --git a/bonobo/util/__init__.py b/bonobo/util/__init__.py
index d07b0b4..b03c0a9 100644
--- a/bonobo/util/__init__.py
+++ b/bonobo/util/__init__.py
@@ -1,4 +1,4 @@
-from bonobo.util.collections import ensure_tuple, sortedlist, tuplize
+from bonobo.util.collections import cast, ensure_tuple, sortedlist, tuplize
 from bonobo.util.compat import deprecated, deprecated_alias
 from bonobo.util.inspect import (
     inspect_node,
@@ -16,6 +16,7 @@ from bonobo.util.objects import (get_name, get_attribute_or_create, ValueHolder)
 # Bonobo's util API
 __all__ = [
     'ValueHolder',
+    'cast',
     'deprecated',
     'deprecated_alias',
     'ensure_tuple',
diff --git a/bonobo/util/api.py b/bonobo/util/api.py
index 1acf5c8..1561207 100644
--- a/bonobo/util/api.py
+++ b/bonobo/util/api.py
@@ -2,6 +2,7 @@ from bonobo.util import get_name
 
 
 class ApiHelper:
+    # TODO __all__ kwarg only
     def __init__(self, __all__):
         self.__all__ = __all__
 
@@ -13,7 +14,8 @@ class ApiHelper:
             from inspect import signature
             parameters = list(signature(x).parameters)
             required_parameters = {'plugins', 'services', 'strategy'}
-            assert parameters[0] == 'graph', 'First parameter of a graph api function must be "graph".'
+            assert len(parameters) > 0 and parameters[
+                0] == 'graph', 'First parameter of a graph api function must be "graph".'
             assert required_parameters.intersection(
                 parameters
             ) == required_parameters, 'Graph api functions must define the following parameters: ' + ', '.join(
diff --git a/bonobo/util/collections.py b/bonobo/util/collections.py
index 745c3b9..de706f4 100644
--- a/bonobo/util/collections.py
+++ b/bonobo/util/collections.py
@@ -26,31 +26,36 @@ def ensure_tuple(tuple_or_mixed, *, cls=tuple):
     if isinstance(tuple_or_mixed, tuple):
         return tuple.__new__(cls, tuple_or_mixed)
 
-    return tuple.__new__(cls, (tuple_or_mixed, ))
+    return tuple.__new__(cls, (tuple_or_mixed,))
 
 
-def tuplize(generator):
-    """
-    Decorates a generator and make it a tuple-returning function. As a side effect, it can also decorate any
-    iterator-returning function to force return value to be a tuple.
+def cast(type_):
+    def _wrap_cast(f):
+        @functools.wraps(f)
+        def _wrapped_cast(*args, **kwargs):
+            nonlocal f, type_
+            return type_(f(*args, **kwargs))
 
-    >>> tuplized_lambda = tuplize(lambda: [1, 2, 3])
-    >>> tuplized_lambda()
-    (1, 2, 3)
+        return _wrapped_cast
 
-    >>> @tuplize
-    ... def my_generator():
-    ...     yield 1
-    ...     yield 2
-    ...     yield 3
-    ...
-    >>> my_generator()
-    (1, 2, 3)
+    return _wrap_cast
 
-    """
 
-    @functools.wraps(generator)
-    def tuplized(*args, **kwargs):
-        return tuple(generator(*args, **kwargs))
+tuplize = cast(tuple)
+tuplize.__doc__ = """
+Decorates a generator and make it a tuple-returning function. As a side effect, it can also decorate any
+iterator-returning function to force return value to be a tuple.
 
-    return tuplized
+>>> tuplized_lambda = tuplize(lambda: [1, 2, 3])
+>>> tuplized_lambda()
+(1, 2, 3)
+
+>>> @tuplize
+... def my_generator():
+...     yield 1
+...     yield 2
+...     yield 3
+...
+>>> my_generator()
+(1, 2, 3)
+"""
diff --git a/bonobo/util/resolvers.py b/bonobo/util/resolvers.py
index 60934d8..5cf2738 100644
--- a/bonobo/util/resolvers.py
+++ b/bonobo/util/resolvers.py
@@ -8,7 +8,7 @@ import os
 import runpy
 
 import bonobo
-from bonobo.util.collections import tuplize
+from bonobo.util import cast
 
 
 class _RequiredModule:
@@ -61,7 +61,7 @@ def _resolve_options(options=None):
     return dict()
 
 
-@tuplize
+@cast(tuple)
 def _resolve_transformations(transformations):
     """
     Resolve a collection of strings into the matching python objects, defaulting to bonobo namespace if no package is provided.
diff --git a/tests/util/test_collections.py b/tests/util/test_collections.py
index 3a1e517..f502afd 100644
--- a/tests/util/test_collections.py
+++ b/tests/util/test_collections.py
@@ -1,5 +1,7 @@
+import pytest
+
 from bonobo.util import sortedlist, ensure_tuple
-from bonobo.util.collections import tuplize
+from bonobo.util.collections import tuplize, cast
 
 
 def test_sortedlist():
@@ -12,12 +14,13 @@ def test_sortedlist():
 
 
 def test_ensure_tuple():
-    assert ensure_tuple('a') == ('a', )
-    assert ensure_tuple(('a', )) == ('a', )
+    assert ensure_tuple('a') == ('a',)
+    assert ensure_tuple(('a',)) == ('a',)
     assert ensure_tuple(()) is ()
 
 
-def test_tuplize():
+@pytest.mark.parametrize('tuplize', [tuplize, cast(tuple)])
+def test_tuplize(tuplize):
     tuplized_lambda = tuplize(lambda: [1, 2, 3])
     assert tuplized_lambda() == (1, 2, 3)