_yaml.py: Report more accurate provenance information

When printing the provenance, show the fully qualified element name
including the junction prefix in the case that the provenance comes
from a subproject.

This makes much more sensible error reporting when reporting errors
which originate from a subproject.

1 files changed, 5 insertions, 1 deletions

diff --git a/buildstream/_yaml.py b/buildstream/_yaml.py
index fc24a223b..5dde9237e 100644
--- a/buildstream/_yaml.py
+++ b/buildstream/_yaml.py
@@ -69,7 +69,11 @@ class Provenance():
 
     # Convert a Provenance to a string for error reporting
     def __str__(self):
-        return "{} [line {:d} column {:d}]".format(self.filename.shortname, self.line, self.col)
+        filename = self.filename.shortname
+        if self.filename.project and self.filename.project.junction:
+            filename = "{}:{}".format(self.filename.project.junction.name, self.filename.shortname)
+
+        return "{} [line {:d} column {:d}]".format(filename, self.line, self.col)
 
     # Abstract method
     def clone(self):