Revert of Track step nesting in StreamEngine.

recipe_modules/step/api.py

 # Copyright 2013 The LUCI Authors. All rights reserved.
 # Use of this source code is governed under the Apache License, Version 2.0
 # that can be found in the LICENSE file.
 
 import contextlib
 
 from recipe_engine import recipe_api
 
 
 # Inherit from RecipeApiPlain because the only thing which is a step is
 # run_from_dict()
 class StepApi(recipe_api.RecipeApiPlain):
   def __init__(self, **kwargs):
     super(StepApi, self).__init__(**kwargs)
     self._step_names = {}
-    self._seen_steps = set()
 
   EXCEPTION = 'EXCEPTION'
   FAILURE = 'FAILURE'
   SUCCESS = 'SUCCESS'
   WARNING = 'WARNING'
 
   @property
   def StepFailure(self):
     """ See recipe_api.py for docs. """
     return recipe_api.StepFailure
@@ skipping 102 matching lines @@
     if cmd is not None:
       command = list(wrapper)
       command += cmd
       kwargs['cmd'] = command
 
     kwargs['timeout'] = timeout
     kwargs['ok_ret'] = ok_ret
 
     # Obtain information from composite step parent.
     compositor = recipe_api._STEP_CONTEXT
-
-    # Calculate our full step name. If a step already has that name, add an
-    # index to the end of it.
-    #
-    # Note that another step could exist with that index already added to it
-    # by the user. If this happens, we'll continue appending indexes until we
-    # have a unique step name.
-    while True:
-      full_name = compositor.get_with_context('name', name)
-      if full_name not in self._seen_steps:
-        break
-
-      step_count = self._step_names.setdefault(full_name, 1) + 1
-      self._step_names[full_name] = step_count
-      name = "%s (%d)" % (name, step_count)
-    self._seen_steps.add(full_name)
-
+    name = compositor.get_with_context('name', name)
     if 'cwd' not in kwargs:
       kwargs['cwd'] = compositor.get('cwd')
     kwargs['env'] = compositor.get_with_context('env', kwargs.get('env', {}))
     kwargs['infra_step'] = compositor.get_with_context(
         'infra_step', bool(infra_step))
     kwargs['step_nest_level'] = compositor.get_with_context('nest_level', 0)
-    kwargs['name'] = full_name
+
+    # Disambiguate repeated names
+    step_count = self._step_names.setdefault(name, 0) + 1
+    self._step_names[name] = step_count
+    if step_count > 1:
+      name = "%s (%d)" % (name, step_count)
+    kwargs['name'] = name
 
     schema = self.make_config()
     schema.set_val(kwargs)
     return self.run_from_dict(self._engine.create_step(schema))
 
   # TODO(martiniss) delete, and make generator_script use **kwargs on step()
   @recipe_api.composite_step
   def run_from_dict(self, dct):
     return self._engine.run_step(dct)