dependency: Check that cached_dep has the 'required' attribute

Closes https://github.com/mesonbuild/meson/issues/992

1 files changed, 2 insertions, 4 deletions

diff --git a/mesonbuild/interpreter.py b/mesonbuild/interpreter.py
index 3044d51..8aedcd7 100644
--- a/mesonbuild/interpreter.py
+++ b/mesonbuild/interpreter.py
@@ -1856,12 +1856,10 @@ requirements use the version keyword argument instead.''')
                     # Cached dep has the wrong version. Check if an external
                     # dependency or a fallback dependency provides it.
                     cached_dep = None
-
             # Don't re-use cached dep if it wasn't required but this one is,
             # so we properly go into fallback/error code paths
-            if 'required' in kwargs and cached_dep is not None:
-                if not cached_dep.required and kwargs.get('required', True):
-                    cached_dep = None
+            if kwargs.get('required', True) and not getattr(cached_dep, 'required', False):
+                cached_dep = None
 
         if cached_dep:
             dep = cached_dep