Fix provenance in error message for undefined variables.

2 files changed, 19 insertions, 4 deletions

diff --git a/buildstream/_variables.py b/buildstream/_variables.py
index 3d84d79e2..b4c920a71 100644
--- a/buildstream/_variables.py
+++ b/buildstream/_variables.py
@@ -87,7 +87,7 @@ class Variables():
             token = match.group(0)
             varname = match.group(1)
 
-            value = _yaml.node_get(variables, str, varname)
+            value = _yaml.node_get(variables, str, varname, default_value=None)
             if value is not None:
                 # We have to check if the inner string has variables
                 # and return unmatches for those
diff --git a/buildstream/element.py b/buildstream/element.py
index b49a75692..c563b79af 100644
--- a/buildstream/element.py
+++ b/buildstream/element.py
@@ -477,7 +477,11 @@ class Element(Plugin):
           name = self.node_subst_member(node, 'name')
         """
         value = self.node_get_member(node, str, member_name, default)
-        return self.__variables.subst(value)
+        try:
+            return self.__variables.subst(value)
+        except LoadError as e:
+            provenance = _yaml.node_get_provenance(node, key=member_name)
+            raise LoadError(e.reason, '{}: {}'.format(provenance, str(e))) from e
 
     def node_subst_list(self, node, member_name):
         """Fetch a list from a node member, substituting any variables in the list
@@ -497,7 +501,14 @@ class Element(Plugin):
         perform variable substitutions.
         """
         value = self.node_get_member(node, list, member_name)
-        return [self.__variables.subst(x) for x in value]
+        ret = []
+        for index, x in enumerate(value):
+            try:
+                ret.append(self.__variables.subst(x))
+            except LoadError as e:
+                provenance = _yaml.node_get_provenance(node, key=member_name, indices=[index])
+                raise LoadError(e.reason, '{}: {}'.format(provenance, str(e))) from e
+        return ret
 
     def node_subst_list_element(self, node, member_name, indices):
         """Fetch the value of a list element from a node member, substituting any variables
@@ -534,7 +545,11 @@ class Element(Plugin):
                   node, 'strings', [ i ])
         """
         value = self.node_get_list_element(node, str, member_name, indices)
-        return self.__variables.subst(value)
+        try:
+            return self.__variables.subst(value)
+        except LoadError as e:
+            provenance = _yaml.node_get_provenance(node, key=member_name, indices=indices)
+            raise LoadError(e.reason, '{}: {}'.format(provenance, str(e))) from e
 
     def compute_manifest(self, *, include=None, exclude=None, orphans=True):
         """Compute and return this element's selective manifest