1 files changed, 77 insertions, 0 deletions
diff --git a/src/buildstream/_options/optionenum.py b/src/buildstream/_options/optionenum.py
new file mode 100644
index 000000000..095b9c356
--- /dev/null
+++ b/src/buildstream/_options/optionenum.py
@@ -0,0 +1,77 @@
+#
+#  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
+from .option import Option, OPTION_SYMBOLS
+
+
+# OptionEnum
+#
+# An enumeration project option
+#
+class OptionEnum(Option):
+
+    OPTION_TYPE = 'enum'
+
+    def load(self, node, allow_default_definition=True):
+        super(OptionEnum, self).load(node)
+
+        valid_symbols = OPTION_SYMBOLS + ['values']
+        if allow_default_definition:
+            valid_symbols += ['default']
+
+        _yaml.node_validate(node, valid_symbols)
+
+        self.values = _yaml.node_get(node, list, 'values', default_value=[])
+        if not self.values:
+            raise LoadError(LoadErrorReason.INVALID_DATA,
+                            "{}: No values specified for {} option '{}'"
+                            .format(_yaml.node_get_provenance(node), self.OPTION_TYPE, self.name))
+
+        # Allow subclass to define the default value
+        self.value = self.load_default_value(node)
+
+    def load_value(self, node, *, transform=None):
+        self.value = _yaml.node_get(node, str, self.name)
+        if transform:
+            self.value = transform(self.value)
+        self.validate(self.value, _yaml.node_get_provenance(node, self.name))
+
+    def set_value(self, value):
+        self.validate(value)
+        self.value = value
+
+    def get_value(self):
+        return self.value
+
+    def validate(self, value, provenance=None):
+        if value not in self.values:
+            prefix = ""
+            if provenance:
+                prefix = "{}: ".format(provenance)
+            raise LoadError(LoadErrorReason.INVALID_DATA,
+                            "{}Invalid value for {} option '{}': {}\n"
+                            .format(prefix, self.OPTION_TYPE, self.name, value) +
+                            "Valid values: {}".format(", ".join(self.values)))
+
+    def load_default_value(self, node):
+        value = _yaml.node_get(node, str, 'default')
+        self.validate(value, _yaml.node_get_provenance(node, 'default'))
+        return value