_options: OptionPool implementation, core project options module

This sub package includes the OptionPool which is the buildstream
facing API for handling project options, loading them, evaluating
expressions based on options and pre-processing loaded YAML.

This also includes an abstract Option class and an implementation
for each supported option type.

1 files changed, 58 insertions, 0 deletions

diff --git a/buildstream/_options/optionarch.py b/buildstream/_options/optionarch.py
new file mode 100644
index 000000000..9cadbebba
--- /dev/null
+++ b/buildstream/_options/optionarch.py
@@ -0,0 +1,58 @@
+#!/usr/bin/env python3
+#
+#  Copyright (C) 2017 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 os
+from .option import OPTION_SYMBOLS
+from .optionenum import OptionEnum
+
+
+# OptionArch
+#
+# An enumeration project option which does not allow
+# definition of a default value, but instead tries to set
+# the default value to the machine architecture introspected
+# using `uname`
+#
+# Note that when using OptionArch in a project, it will automatically
+# bail out of the host machine `uname` reports a machine architecture
+# not supported by the project, in the case that no option was
+# specifically specified
+#
+class OptionArch(OptionEnum):
+
+    OPTION_TYPE = 'arch'
+
+    def load(self, node):
+        super(OptionArch, self).load(node, allow_default_definition=False)
+
+    def load_default_value(self, node):
+        _, _, _, _, machine_arch = os.uname()
+        return machine_arch
+
+    def resolve(self):
+
+        # Validate that the default machine arch reported by uname() is
+        # explicitly supported by the project, only if it was not
+        # overridden by user configuration or cli.
+        #
+        # If the value is specified on the cli or user configuration,
+        # then it will already be valid.
+        #
+        self.validate(self.value)