Fixes cast problem when type changed but we got NOT_MODIFIED token.

bonobo/execution/contexts/node.py

@@ -342,6 +342,8 @@ class NodeExecutionContext(BaseContext, WithStatistics):
             # TODO: parse flags to check constraints are respected (like not modified alone, etc.)
 
             if F_NOT_MODIFIED in _flags:
+                if self._output_type:
+                    return ensure_tuple(_input, cls=self._output_type)
                 return _input
 
             if F_INHERIT in _flags:

bonobo/nodes/io/csv.py

@@ -6,7 +6,7 @@ from bonobo.constants import NOT_MODIFIED
 from bonobo.nodes.io.base import FileHandler
 from bonobo.nodes.io.file import FileReader, FileWriter
 from bonobo.util import ensure_tuple
-from bonobo.util.collections import tuple_or_const
+from bonobo.util.collections import coalesce, tuple_or_const
 
 
 class CsvHandler(FileHandler):
@@ -105,7 +105,7 @@ class CsvWriter(FileWriter, CsvHandler):
 
     def write(self, file, context, *values, fs):
         context.setdefault("lineno", 0)
-        fields = context.get_input_fields() if self.fields is None else self.fields
+        fields = coalesce(self.fields, context.get_input_fields())
 
         if not context.lineno:
             context.writer = self.writer_factory(file)

bonobo/structs/graphs.py

@@ -8,19 +8,11 @@ from graphviz.dot import Digraph
 
 from bonobo.constants import BEGIN
 from bonobo.util import get_name
+from bonobo.util.collections import coalesce
 
 GraphRange = namedtuple("GraphRange", ["graph", "input", "output"])
 
 
-def coalesce(*values):
-    if not len(values):
-        raise ValueError("Cannot coalesce an empty list of arguments.")
-    for value in values:
-        if value is not None:
-            return value
-    return values[-1]
-
-
 class GraphCursor:
     @property
     def input(self):

bonobo/util/collections.py

@@ -105,3 +105,17 @@ iterator-returning function to force return value to be a tuple.
 >>> my_generator()
 (1, 2, 3)
 """
+
+
+def coalesce(*values):
+    """
+    Returns the first argument which is not None, or None if all arguments are None.
+
+    """
+
+    if not len(values):
+        raise ValueError("Cannot coalesce an empty list of arguments.")
+    for value in values:
+        if value is not None:
+            return value
+    return None