modules/gnome: Allow gdbus_annotations to take an empty list again

This was allows up to 0.61.0 (including with the initial type
annotations), but was accidentally broken by fixes for other bugs in
0.61.1.

Fixes: #9883

mesonbuild/modules/gnome.py

@@ -224,12 +224,13 @@ _MK_ENUMS_COMMON_KWS: T.List[KwargInfo] = [
 ]
 
 def annotations_validator(annotations: T.List[T.Union[str, T.List[str]]]) -> T.Optional[str]:
-
     """Validate gdbus-codegen annotations argument"""
 
     badlist = 'must be made up of 3 strings for ELEMENT, KEY, and VALUE'
 
-    if all(isinstance(annot, str) for annot in annotations):
+    if not annotations:
+        return None
+    elif all(isinstance(annot, str) for annot in annotations):
         if len(annotations) == 3:
             return None
         else:

test cases/frameworks/7 gnome/gdbus/meson.build

@@ -6,6 +6,16 @@ gdbus_src = gnome.gdbus_codegen('generated-gdbus-no-docbook',
     ['com.example.Hello()', 'org.freedesktop.DBus.Deprecated', 'true']
   ],
 )
+
+# check that empty annotations work
+gdbus_src2 = gnome.gdbus_codegen(
+  'generated-gdbus-no-docbook2',
+  'data/com.example.Sample.xml',
+  interface_prefix : 'com.example.',
+  namespace : 'Sample',
+  annotations : [],
+)
+
 assert(gdbus_src.length() == 2, 'expected 2 targets')
 assert(gdbus_src[0].full_path().endswith('.c'), 'expected 1 c source file')
 assert(gdbus_src[1].full_path().endswith('.h'), 'expected 1 c header file')