configs/manager.py: Fix the bug that breaks specifications loading

The "filter()" returns an iterator, that is consumed after the use,
therefore, the "specfiles" is used by the print under "DEBUG_FG21SIM".
Then "specfiles" is empty and thus prevents the reading of the
specification files.

1 files changed, 4 insertions, 1 deletions

diff --git a/fg21sim/configs/manager.py b/fg21sim/configs/manager.py
index 5ee4ecf..3206c29 100644
--- a/fg21sim/configs/manager.py
+++ b/fg21sim/configs/manager.py
@@ -28,7 +28,10 @@ logger = logging.getLogger(__name__)
 def _get_configspec():
     """Found and read all the configuration specifications"""
     files = sorted(pkg_resources.resource_listdir(__name__, ""))
-    specfiles = filter(lambda fn: fn.endswith(".conf.spec"), files)
+    # NOTE:
+    # Explicit convert the filter results to a list, since the returned
+    # iterator can ONLY be used ONCE.
+    specfiles = list(filter(lambda fn: fn.endswith(".conf.spec"), files))
     if os.environ.get("DEBUG_FG21SIM"):
         print("DEBUG: Found config specifications: %s" % ", ".join(specfiles),
               file=sys.stderr)