_options: Support transform function for variable substitution

5 files changed, 15 insertions, 7 deletions

diff --git a/buildstream/_options/option.py b/buildstream/_options/option.py
index 357eb98d3..05c56e582 100644
--- a/buildstream/_options/option.py
+++ b/buildstream/_options/option.py
@@ -71,8 +71,9 @@ class Option():
     # Args:
     #    node (Mapping): The YAML loaded key/value dictionary
     #                    to load the value from
+    #    transform (callbable): Transform function for variable substitution
     #
-    def load_value(self, node):
+    def load_value(self, node, *, transform=None):
         pass  # pragma: nocover
 
     # set_value()
diff --git a/buildstream/_options/optionbool.py b/buildstream/_options/optionbool.py
index db01340e4..e0e1474d9 100644
--- a/buildstream/_options/optionbool.py
+++ b/buildstream/_options/optionbool.py
@@ -37,8 +37,11 @@ class OptionBool(Option):
         _yaml.node_validate(node, OPTION_SYMBOLS + ['default'])
         self.value = _yaml.node_get(node, bool, 'default')
 
-    def load_value(self, node):
-        self.value = _yaml.node_get(node, bool, self.name)
+    def load_value(self, node, *, transform=None):
+        if transform:
+            self.set_value(transform(_yaml.node_get(node, str, self.name)))
+        else:
+            self.value = _yaml.node_get(node, bool, self.name)
 
     def set_value(self, value):
         if value == 'True' or value == 'true':
diff --git a/buildstream/_options/optionenum.py b/buildstream/_options/optionenum.py
index 2ba8552d7..bc21bd81c 100644
--- a/buildstream/_options/optionenum.py
+++ b/buildstream/_options/optionenum.py
@@ -49,8 +49,10 @@ class OptionEnum(Option):
         # Allow subclass to define the default value
         self.value = self.load_default_value(node)
 
-    def load_value(self, 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):
diff --git a/buildstream/_options/optionflags.py b/buildstream/_options/optionflags.py
index 49ec70d85..84ecc1360 100644
--- a/buildstream/_options/optionflags.py
+++ b/buildstream/_options/optionflags.py
@@ -50,8 +50,10 @@ class OptionFlags(Option):
         self.value = _yaml.node_get(node, list, 'default', default_value=[])
         self.validate(self.value, _yaml.node_get_provenance(node, 'default'))
 
-    def load_value(self, node):
+    def load_value(self, node, *, transform=None):
         self.value = _yaml.node_get(node, list, self.name)
+        if transform:
+            self.value = [transform(x) for x in self.value]
         self.value = sorted(self.value)
         self.validate(self.value, _yaml.node_get_provenance(node, self.name))
 
diff --git a/buildstream/_options/optionpool.py b/buildstream/_options/optionpool.py
index f38682aec..9d7228f27 100644
--- a/buildstream/_options/optionpool.py
+++ b/buildstream/_options/optionpool.py
@@ -82,7 +82,7 @@ class OptionPool():
     # Args:
     #    node (dict): The loaded YAML options
     #
-    def load_yaml_values(self, node):
+    def load_yaml_values(self, node, *, transform=None):
         for option_name, _ in _yaml.node_items(node):
             try:
                 option = self.options[option_name]
@@ -90,7 +90,7 @@ class OptionPool():
                 p = _yaml.node_get_provenance(node, option_name)
                 raise LoadError(LoadErrorReason.INVALID_DATA,
                                 "{}: Unknown option '{}' specified".format(p, option_name))
-            option.load_value(node)
+            option.load_value(node, transform=transform)
 
     # load_cli_values()
     #