Add support for LUCI_CONTEXT.

recipe_engine/recipe_api.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.
 
 from __future__ import absolute_import
 import bisect
 import collections
 import contextlib
 import copy
 import json
@@ skipping 157 matching lines @@
     return copy.deepcopy(self._engine.properties)
 
 
 class StepClient(object):
   """A recipe engine client representing step running and introspection."""
 
   IDENT = 'step'
 
 
   class StepConfig(collections.namedtuple('_StepConfig', (
-      'name', 'base_name', 'cmd', 'cwd', 'env', 'env_prefixes',
+      'name', 'base_name', 'cmd', 'cwd', 'env', 'env_prefixes', 'luci_context',
       'allow_subannotations', 'trigger_specs', 'timeout', 'infra_step',
       'stdout', 'stderr', 'stdin', 'ok_ret', 'step_test_data', 'nest_level'))):
 
     """
     StepConfig is the representation of a raw step as the recipe_engine sees it.
     You should use the standard 'step' recipe module, which will construct and
     pass this data to the engine for you, instead. The only reason why you would
     need to worry about this object is if you're modifying the step module
     itself.
 
     Fields:
       name (str): name of the step, will appear in buildbots waterfall
       base_name (str): the base name of the step. If the step has a derived
           name (e.g., nested may be concatenated with its parent), this is the
           name component of just this step. If None, this will be set to "name".
       cmd: command to run. Acceptable types: str, Path, Placeholder, or None.
       cwd (str or None): absolute path to working directory for the command
       env (dict): overrides for environment variables, described above.
       env_prefixes (dict): environment prefix variables, mapping environment
         variable names to EnvPrefix values.
+      luci_context (dict): overrides for the LUCI_CONTEXT dict.
       allow_subannotations (bool): if True, lets the step emit its own
           annotations. NOTE: Enabling this can cause some buggy behavior. Please
           strongly consider using step_result.presentation instead. If you have
           questions, please contact infra-dev@chromium.org.
       trigger_specs: a list of trigger specifications, see also _trigger_builds.
       timeout: if not None, a datetime.timedelta for the step timeout.
       infra_step: if True, this is an infrastructure step. Failures will raise
           InfraFailure instead of StepFailure.
       stdout: Placeholder to put step stdout into. If used, stdout won't appear
           in annotator's stdout (and |allow_subannotations| is ignored).
@@ skipping 50 matching lines @@
                     for k, v in self.prefixes.iteritems()}
         return pprint.pformat(rendered, width=1024)
 
 
     _RENDER_WHITELIST=frozenset((
       'cmd',
     ))
 
     _RENDER_BLACKLIST=frozenset((
       'base_name',
+      'luci_context',  # it's ambient and used only for advanced stuff

[iannucci, 2017/08/04 18:55:50]

This blacklist is used for excluding the entry from the expectations; I don't
think we want that.

Additionally, you may want to tweak
https://github.com/luci/recipes-py/blob/master/recipe_engine/step_runner.py#L290
to prevent it from dumping this to stdout (e.g. see the little preamble thingy
here:
https://luci-logdog.appspot.com/v/?s=chromium%2Fbb%2Ftryserver.chromium.linux...
).

Can you also add a test (e.g. to
https://github.com/luci/recipes-py/blob/master/recipe_engine/unittests/run_te...)
which runs some luci_context-using recipe for real and asserts that it doesn't
show up in stdout? E.g. put some value like "super_secret_token" in it and
assert that it's not in stdout. Regressing this would be bad.

       'nest_level',
       'ok_ret',
       'step_test_data',
     ))
 
     def __new__(cls, **kwargs):
       for field in cls._fields:
         kwargs.setdefault(field, None)
       sc = super(StepClient.StepConfig, cls).__new__(cls, **kwargs)
 
       return sc._replace(
           cmd=[(x if isinstance(x, Placeholder) else str(x))
                for x in (sc.cmd or ())],
           cwd=(str(sc.cwd) if sc.cwd else (None)),
           env=sc.env or {},
           env_prefixes=sc.env_prefixes or cls.EnvPrefix.empty(),
+          luci_context=sc.luci_context or {},
           base_name=sc.base_name or sc.name,
           allow_subannotations=bool(sc.allow_subannotations),
           trigger_specs=sc.trigger_specs or (),
           infra_step=bool(sc.infra_step),
           ok_ret=frozenset(sc.ok_ret or (0,)),
           nest_level=int(sc.nest_level or 0),
       )
 
     def render_to_dict(self):
       sc = self._replace(
@@ skipping 799 matching lines @@
   def bind(self, name, property_type, full_decl_name):
     """
     Gets the BoundProperty version of this Property. Requires a name.
     """
     return BoundProperty(
       self._default, self.help, self.kind, name, property_type, full_decl_name,
       self.param_name)
 
 class UndefinedPropertyException(TypeError):
   pass