context: Move 'CacheBuildTrees' to a FastEnum

This allows removing completely the '_node_get_option_str' on context
and ensures every method relying on a few set of keys set their errors
consistently

1 files changed, 2 insertions, 30 deletions

diff --git a/src/buildstream/_context.py b/src/buildstream/_context.py
index 4d68ef222..c1a3b0619 100644
--- a/src/buildstream/_context.py
+++ b/src/buildstream/_context.py
@@ -29,7 +29,7 @@ from ._platform import Platform
 from ._artifactcache import ArtifactCache
 from ._sourcecache import SourceCache
 from ._cas import CASCache, CASQuota, CASCacheUsage
-from .types import _SchedulerErrorAction
+from .types import _CacheBuildTrees, _SchedulerErrorAction
 from ._workspaces import Workspaces, WorkspaceProjectCache
 from .node import Node
 from .sandbox import SandboxRemote
@@ -299,8 +299,7 @@ class Context():
         self.pull_buildtrees = cache.get_bool('pull-buildtrees')
 
         # Load cache build trees configuration
-        self.cache_buildtrees = _node_get_option_str(
-            cache, 'cache-buildtrees', ['always', 'auto', 'never'])
+        self.cache_buildtrees = cache.get_enum('cache-buildtrees', _CacheBuildTrees)
 
         # Load logging config
         logging = defaults.get_mapping('logging')
@@ -503,30 +502,3 @@ class Context():
         if self._casquota is None:
             self._casquota = CASQuota(self)
         return self._casquota
-
-
-# _node_get_option_str()
-#
-# Like Node.get_scalar().as_str(), but also checks value is one of the allowed option
-# strings. Fetches a value from a dictionary node, and makes sure it's one of
-# the pre-defined options.
-#
-# Args:
-#    node (dict): The dictionary node
-#    key (str): The key to get a value for in node
-#    allowed_options (iterable): Only accept these values
-#
-# Returns:
-#    The value, if found in 'node'.
-#
-# Raises:
-#    LoadError, when the value is not of the expected type, or is not found.
-#
-def _node_get_option_str(node, key, allowed_options):
-    result_node = node.get_scalar(key)
-    result = result_node.as_str()
-    if result not in allowed_options:
-        provenance = result_node.get_provenance()
-        raise LoadError("{}: {} should be one of: {}".format(provenance, key, ", ".join(allowed_options)),
-                        LoadErrorReason.INVALID_DATA)
-    return result