[step_runner] run _merge_envs in simulation too.

recipe_engine/step_runner.py

 # Copyright 2016 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 calendar
 import collections
 import contextlib
 import datetime
 import itertools
 import json
@@ skipping 388 matching lines @@
 
     # Convert when_timestamp to UNIX timestamp.
     when = change.get('when_timestamp')
     if isinstance(when, datetime.datetime):
       when = calendar.timegm(when.utctimetuple())
       change['when_timestamp'] = when
 
     return change
 
 
+class fakeEnviron(object):

[nodir, 2017/05/31 21:49:03]

when reading this without context, it is hard to understand what's the
purpose/responsibility of this class. Please maybe add comments explaining what
you explained offline :)

+  def __init__(self):
+    self.data = {}
+
+  def __getitem__(self, key):
+    return '<%s>' % key
+
+  def __delitem__(self, key):
+    self.data[key] = None
+
+  def __contains__(self, key):
+    return True
+
+  def __setitem__(self, key, value):
+    self.data[key] = value
+
+  def copy(self):
+    return self
+
+
 class SimulationStepRunner(StepRunner):
   """Pretends to run steps, instead recording what would have been run.
 
   This is the main workhorse of recipes.py simulation_test.  Returns the log of
   steps that would have been run in steps_ran.  Uses test_data to mock return
   values.
   """
 
   def __init__(self, stream_engine, test_data, annotator):
     self._test_data = test_data
     self._stream_engine = stream_engine
     self._annotator = annotator
     self._step_history = collections.OrderedDict()
 
   @property
   def stream_engine(self):
     return self._stream_engine
 
   def open_step(self, step_config):
     try:
       test_data_fn = step_config.step_test_data or recipe_test_api.StepTestData
       step_test = self._test_data.pop_step_test_data(step_config.name,
                                                      test_data_fn)
       rendered_step = render_step(step_config, step_test)
+      step_env = _merge_envs(fakeEnviron(), (rendered_step.config.env or {}))
+      rendered_step = rendered_step._replace(
+        config=rendered_step.config._replace(env=step_env.data))
       step_config = None  # Make sure we use rendered step config.
 
       # Layer the simulation step on top of the given stream engine.
       step_stream = self._stream_engine.new_step_stream(rendered_step.config)
     except:
       with self.stream_engine.make_step_stream('Step Preparation Exception') as s:
         s.set_step_status('EXCEPTION')
         with s.new_log_stream('exception') as l:
           l.write_split(traceback.format_exc())
       raise
@@ skipping 305 matching lines @@
   supplied command, and only uses the |env| kwarg for modifying the environment
   of the child process.
   """
   saved_path = os.environ['PATH']
   try:
     if path is not None:
       os.environ['PATH'] = path
     yield
   finally:
     os.environ['PATH'] = saved_path