Remove all direct config access in task.py.

Testing Done:
CI passes: https://travis-ci.org/pantsbuild/pants/builds/52067414.

Reviewed at https://rbcommons.com/s/twitter/r/1827/

src/python/pants/backend/core/tasks/task.py

@@ -140,21 +140,23 @@ def __init__(self, *args, **kwargs):
     """
     self.context = context
     self._workdir = workdir
+    # TODO: It would be nice to use self.get_options().cache_key_gen_version here, because then
+    # we could have a separate value for each scope if we really wanted to. However we can't
+    # access per-task options in Task.__init__ because GroupTask.__init__ calls it with the
+    # group task's scope, which isn't currently in the known scopes we generate options for.
     self._cache_key_generator = CacheKeyGenerator(
-        context.config.getdefault('cache_key_gen_version', default='200'))
+      self.context.options.for_global_scope().cache_key_gen_version)
     self._read_artifact_cache_spec = None
     self._write_artifact_cache_spec = None
     self._artifact_cache = None
     self._artifact_cache_setup_lock = threading.Lock()
 
     self._cache_key_errors = set()
 
-    default_invalidator_root = os.path.join(
-      self.context.options.for_global_scope().pants_workdir, 'build_invalidator')
-    suffix_type = self.__class__.__name__
     self._build_invalidator_dir = os.path.join(
-        context.config.get('tasks', 'build_invalidator', default=default_invalidator_root),
-        suffix_type)
+      self.context.options.for_global_scope().pants_workdir,
+      'build_invalidator',
+      self.__class__.__name__)
 
   def get_options(self):
     """Returns the option values for this task's scope."""
@@ -198,7 +200,7 @@ def _setup_artifact_cache_from_specs(self, read_spec, write_spec):
   def _create_artifact_cache(self, spec, action):
     if len(spec) > 0:
       pants_workdir = self.context.options.for_global_scope().pants_workdir
-      compression = self.context.config.getint('cache', 'compression', default=5)
+      compression = self.get_options().cache_compression
       my_name = self.__class__.__name__
       return create_artifact_cache(
         log=self.context.log,

src/python/pants/option/global_options.py

@@ -39,6 +39,9 @@ def register_global_options(register):
   register('--exclude-target-regexp', action='append', default=[], metavar='<regexp>',
            help='Regex pattern to exclude from the target list (useful in conjunction with ::). '
                 'Multiple patterns may be specified by setting this flag multiple times.')
+  # TODO: When we have a model for 'subsystems', create one for artifact caching and move these
+  # options to there. When we do that, also drop the cumbersome word 'artifact' from these
+  # option names. There's only one cache concept that users care about.
   register('--read-from-artifact-cache', action='store_true', default=True,
            help='Read build artifacts from cache, if available.')
   register('--read-artifact-caches', type=Options.list,
@@ -53,6 +56,10 @@ def register_global_options(register):
                 'choose from.')
   register('--overwrite-cache-artifacts', action='store_true',
            help='If writing to build artifacts to cache, overwrite (instead of skip) existing.')
+  register('--cache-key-gen-version', advanced=True, default='200',
+           help='The cache key generation. Bump this to invalidate every artifact.')
+  register('--cache-compression', advanced=True, type=int, default=5,
+           help='The gzip compression level for created artifacts.')
   register('--print-exception-stacktrace', action='store_true',
            help='Print to console the full exception stack trace if encountered.')
   register('--fail-fast', action='store_true',

src/python/pants/option/migrate_config.py

@@ -126,6 +126,8 @@
   ('ide', 'extra_jvm_source_paths'): ('idea', 'extra_jvm_source_paths'),
   ('ide', 'extra_jvm_test_paths'): ('idea', 'extra_jvm_test_paths'),
   ('ide', 'debug_port'): ('idea', 'debug_port'),
+
+  ('cache', 'compression'): ('DEFAULT', 'cache_compression'),
 }
 
 notes = {
@@ -161,7 +163,9 @@
                                    'idea and eclipse goals.',
   ('ide', 'debug_port'):       'debug_port now must be specified separately for idea and eclipse '
                                'goals.  Also, IDE goals now use their own debug setting and do not '
-                               'inherit from jvm configuration.'
+                               'inherit from jvm configuration.',
+
+  ('tasks', 'build_invalidator'): 'This is no longer configurable. The default will be used.',
 }
 
 

tests/python/pants_test/base_test.py

@@ -115,7 +115,8 @@ def setUp(self):
     self.options[''] = {
       'pants_workdir': os.path.join(self.build_root, '.pants.d'),
       'pants_supportdir': os.path.join(self.build_root, 'build-support'),
-      'pants_distdir': os.path.join(self.build_root, 'dist')
+      'pants_distdir': os.path.join(self.build_root, 'dist'),
+      'cache_key_gen_version': '0-test'
     }
     BuildRoot().path = self.build_root