[buildstream] 02/10: element.py: try-except nicely in 'node_substitute_variables'

[tv...@apache.org]

This is an automated email from the ASF dual-hosted git repository.

tvb pushed a commit to branch bschubert/more-mypy
in repository https://gitbox.apache.org/repos/asf/buildstream.git

commit d513a4c7c486fe10596df48220379da623f5d876
Author: Benjamin Schubert <co...@benschubert.me>
AuthorDate: Thu Oct 10 18:34:54 2019 +0100

    element.py: try-except nicely in 'node_substitute_variables'
    
    This adds a nicer try-except around the 'node_substitute_variables' method
    in order to get nicer error reporting to users.
---
 src/buildstream/element.py | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/src/buildstream/element.py b/src/buildstream/element.py
index 4e579ff..f95ac9b 100644
--- a/src/buildstream/element.py
+++ b/src/buildstream/element.py
@@ -545,6 +545,9 @@ class Element(Plugin):
         Returns:
            The value with all variables replaced
 
+        Raises:
+           :class:`.LoadError`: When the node doesn't contain a string or a variable was not found.
+
         **Example:**
 
         .. code:: python
@@ -553,7 +556,11 @@ class Element(Plugin):
           # variables in the returned string
           name = self.node_substitute_variables(node.get_str('name'))
         """
-        return self.__variables.subst(node.as_str())
+        try:
+            return self.__variables.subst(node.as_str())
+        except LoadError as e:
+            provenance = node.get_provenance()
+            raise LoadError('{}: {}'.format(provenance, e), e.reason, detail=e.detail) from e
 
     def node_subst_member(self, node: 'MappingNode[str, Any]', member_name: str, default: str = _node_sentinel) -> Any:
         """Fetch the value of a string node member, substituting any variables