Make output placeholders like json.output index-able by name.

recipe_engine/util.py

Index: recipe_engine/util.py
diff --git a/recipe_engine/util.py b/recipe_engine/util.py
index 1bc3f4e54cfd6935288c60c188ce1e99d58e7575..fa92dc5210de9a30d1f117949b2c8302e79981c8 100644
--- a/recipe_engine/util.py
+++ b/recipe_engine/util.py
@@ -35,8 +35,11 @@ class ModuleInjectionSite(object):
 
 class Placeholder(object):
   """Base class for command line argument placeholders. Do not use directly."""
-  def __init__(self):
-    self.name_pieces = None
+  def __init__(self, name=None):
+    if name is not None:
+      assert isinstance(name, basestring)
+    self.name = name
+    self.namespaces = None
 
   @property
   def backing_file(self):  # pragma: no cover
@@ -62,9 +65,28 @@ class Placeholder(object):
     pass
 
   @property
-  def name(self):
-    assert self.name_pieces
-    return "%s.%s" % self.name_pieces
+  def label(self):
+    if self.name is None:
+      return "%s.%s" % self.namespaces

[iannucci, 2016/03/22 22:54:24]

%s.%s[DEFAULT]

maybe?

[stgao, 2016/03/22 23:40:25]

Maybe not, this will change the current behavior in links.
I'd keep it as to avoid possible break and avoid updating lots of expectation
files for this.

+    else:
+      return "%s.%s[%s]" % (self.namespaces[0], self.namespaces[1], self.name)
+
+
+class InputPlaceholder(Placeholder):
+  """Base class for json/raw_io input placeholders. Do not use directly."""
+  def result(self, presentation, test):
+    """Returned value will be discarded."""
+    pass
+  result.__doc__ = Placeholder.result.__doc__
+
+
+class OutputPlaceholder(Placeholder):
+  """Base class for json/raw_io output placeholders. Do not use directly."""
+
+  def result(self, presentation, test):
+    """Returned value will be added to the step result."""
+    pass
+  result.__doc__ = Placeholder.result.__doc__
 
 
 class InputPlaceholder(Placeholder):
@@ -113,7 +135,7 @@ def returns_placeholder(func):
   def inner(self, *args, **kwargs):
     ret = static_call(self, func, *args, **kwargs)
     assert isinstance(ret, Placeholder)
-    ret.name_pieces = (self.name, static_name(self, func))
+    ret.namespaces = (self.name, static_name(self, func))
     return ret
   # prevent this placeholder-returning function from becoming a composite_step.
   inner._non_step = True # pylint: disable=protected-access