Move utils._generate_key() into a new 'cachekey' module

This avoids a circular dependency between the 'utils' and '_yaml'
modules.

5 files changed, 50 insertions, 23 deletions

diff --git a/buildstream/_cachekey.py b/buildstream/_cachekey.py
new file mode 100644
index 000000000..3d0c19b44
--- /dev/null
+++ b/buildstream/_cachekey.py
@@ -0,0 +1,43 @@
+#!/usr/bin/env python3
+#
+#  Copyright (C) 2018 Codethink Limited
+#
+#  This program is free software; you can redistribute it and/or
+#  modify it under the terms of the GNU Lesser General Public
+#  License as published by the Free Software Foundation; either
+#  version 2 of the License, or (at your option) any later version.
+#
+#  This library is distributed in the hope that it will be useful,
+#  but WITHOUT ANY WARRANTY; without even the implied warranty of
+#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.	 See the GNU
+#  Lesser General Public License for more details.
+#
+#  You should have received a copy of the GNU Lesser General Public
+#  License along with this library. If not, see <http://www.gnu.org/licenses/>.
+#
+#  Authors:
+#        Tristan Van Berkom <tristan.vanberkom@codethink.co.uk>
+
+
+import hashlib
+import pickle
+
+from . import _yaml
+
+
+# generate_key()
+#
+# Generate an sha256 hex digest from the given value. The value
+# can be a simple value or recursive dictionary with lists etc,
+# anything simple enough to serialize.
+#
+# Args:
+#    value: A value to get a key for
+#
+# Returns:
+#    (str): An sha256 hex digest of the given value
+#
+def generate_key(value):
+    ordered = _yaml.node_sanitize(value)
+    string = pickle.dumps(ordered)
+    return hashlib.sha256(string).hexdigest()
diff --git a/buildstream/_context.py b/buildstream/_context.py
index 08ce83adf..6d0a19bde 100644
--- a/buildstream/_context.py
+++ b/buildstream/_context.py
@@ -22,10 +22,10 @@ import os
 import datetime
 from collections import deque, Mapping
 from contextlib import contextmanager
+from . import _cachekey
 from . import _signals
 from . import _site
 from . import _yaml
-from . import utils
 from ._exceptions import LoadError, LoadErrorReason, BstError
 from ._message import Message, MessageType
 from ._profile import Topics, profile_start, profile_end
@@ -253,7 +253,7 @@ class Context():
         if self._cache_key is None:
 
             # Anything that alters the build goes into the unique key
-            self._cache_key = utils._generate_key({})
+            self._cache_key = _cachekey.generate_key({})
 
         return self._cache_key
 
diff --git a/buildstream/_project.py b/buildstream/_project.py
index fc8fa06f9..50f5d9c57 100644
--- a/buildstream/_project.py
+++ b/buildstream/_project.py
@@ -22,6 +22,7 @@ import os
 import multiprocessing  # for cpu_count()
 from collections import Mapping
 from . import utils
+from . import _cachekey
 from . import _site
 from . import _yaml
 from ._profile import Topics, profile_start, profile_end
@@ -402,6 +403,6 @@ class Project():
 
             # Anything that alters the build goes into the unique key
             # (currently nothing here)
-            self._cache_key = utils._generate_key({})
+            self._cache_key = _cachekey.generate_key({})
 
         return self._cache_key
diff --git a/buildstream/element.py b/buildstream/element.py
index ef5e9ea76..8c7fad71d 100644
--- a/buildstream/element.py
+++ b/buildstream/element.py
@@ -40,6 +40,7 @@ from . import Plugin, Consistency
 from ._project import BST_ARTIFACT_VERSION as BST_CORE_ARTIFACT_VERSION
 from . import SandboxFlags
 from . import utils
+from . import _cachekey
 from . import _signals
 from . import _site
 from ._platform import Platform
@@ -900,7 +901,7 @@ class Element(Plugin):
 
         context = self._get_context()
         project = self._get_project()
-        return utils._generate_key({
+        return _cachekey.generate_key({
             'artifact-version': "{}.{}".format(BST_CORE_ARTIFACT_VERSION,
                                                self.BST_ARTIFACT_VERSION),
             'context': context._get_cache_key(),
diff --git a/buildstream/utils.py b/buildstream/utils.py
index 9c65d8e74..2b6c4517c 100644
--- a/buildstream/utils.py
+++ b/buildstream/utils.py
@@ -40,7 +40,6 @@ import pkg_resources
 import psutil
 
 from . import _signals
-from . import _yaml
 from ._exceptions import BstError, ErrorDomain
 
 
@@ -206,6 +205,7 @@ def sha256sum(filename):
         with open(filename, "rb") as f:
             for chunk in iter(lambda: f.read(4096), b""):
                 h.update(chunk)
+
     except OSError as e:
         raise UtilError("Failed to get a checksum of file '{}': {}"
                         .format(filename, e)) from e
@@ -734,24 +734,6 @@ def _relative_symlink_target(root, symlink, target):
         return target
 
 
-# _generate_key()
-#
-# Generate an sha256 hex digest from the given value. The value
-# can be a simple value or recursive dictionary with lists etc,
-# anything simple enough to serialize.
-#
-# Args:
-#    value: A value to get a key for
-#
-# Returns:
-#    (str): An sha256 hex digest of the given value
-#
-def _generate_key(value):
-    ordered = _yaml.node_sanitize(value)
-    string = pickle.dumps(ordered)
-    return hashlib.sha256(string).hexdigest()
-
-
 # _set_deterministic_user()
 #
 # Set the uid/gid for every file in a directory tree to the process'