1 files changed, 84 insertions, 0 deletions
diff --git a/src/buildstream/_options/optionarch.py b/src/buildstream/_options/optionarch.py
new file mode 100644
index 000000000..0e2963c84
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+++ b/src/buildstream/_options/optionarch.py
@@ -0,0 +1,84 @@
+#
+#  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>
+
+from .. import _yaml
+from .._exceptions import LoadError, LoadErrorReason, PlatformError
+from .._platform import Platform
+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):
+        arch = Platform.get_host_arch()
+
+        default_value = None
+
+        for index, value in enumerate(self.values):
+            try:
+                canonical_value = Platform.canonicalize_arch(value)
+                if default_value is None and canonical_value == arch:
+                    default_value = value
+                    # Do not terminate the loop early to ensure we validate
+                    # all values in the list.
+            except PlatformError as e:
+                provenance = _yaml.node_get_provenance(node, key='values', indices=[index])
+                prefix = ""
+                if provenance:
+                    prefix = "{}: ".format(provenance)
+                raise LoadError(LoadErrorReason.INVALID_DATA,
+                                "{}Invalid value for {} option '{}': {}"
+                                .format(prefix, self.OPTION_TYPE, self.name, e))
+
+        if default_value is None:
+            # Host architecture is not supported by the project.
+            # Do not raise an error here as the user may override it.
+            # If the user does not override it, an error will be raised
+            # by resolve()/validate().
+            default_value = arch
+
+        return default_value
+
+    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)