plugins/sources/_downloadablefilesource.py: Exclude a line from coverage

When fetching a downloadable source, we make a defensive check
to avoid redundant download at fetch() time by checking if it's
already cached, but fetch() will never be called if the source
is already cached.

1 files changed, 6 insertions, 1 deletions

diff --git a/buildstream/plugins/sources/_downloadablefilesource.py b/buildstream/plugins/sources/_downloadablefilesource.py
index 99eab340e..51b2a4c19 100644
--- a/buildstream/plugins/sources/_downloadablefilesource.py
+++ b/buildstream/plugins/sources/_downloadablefilesource.py
@@ -59,8 +59,13 @@ class DownloadableFileSource(Source):
             return new_ref
 
     def fetch(self):
+
+        # Just a defensive check, it is impossible for the
+        # file to be already cached because Source.fetch() will
+        # not be called if the source is already Consistency.CACHED.
+        #
         if os.path.isfile(self._get_mirror_file()):
-            return
+            return  # pragma: nocover
 
         # Download the file, raise hell if the sha256sums don't match,
         # and mirror the file otherwise.