gnome.gdbus_codegen: Handle XML docbook in subdirs

Closes https://github.com/mesonbuild/meson/issues/3870

mesonbuild/build.py

@@ -1741,7 +1741,7 @@ class CustomTarget(Target):
             if i.strip() == '':
                 raise InvalidArguments('Output must not consist only of whitespace.')
             if has_path_sep(i):
-                raise InvalidArguments('Output must not contain a path segment.')
+                raise InvalidArguments('Output {!r} must not contain a path segment.'.format(i))
             if '@INPUT@' in i or '@INPUT0@' in i:
                 m = 'Output cannot contain @INPUT@ or @INPUT0@, did you ' \
                     'mean @PLAINNAME@ or @BASENAME@?'

mesonbuild/modules/gnome.py

@@ -1017,7 +1017,7 @@ This will become a hard error in the future.''')
             output = namebase + '-docbook'
             outputs = []
             for f in xml_files:
-                outputs.append('{}-{}'.format(docbook, f))
+                outputs.append('{}-{}'.format(docbook, os.path.basename(str(f))))
 
             if mesonlib.version_compare(glib_version, '>= 2.56.2'):
                 custom_kwargs = {'input': xml_files,

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

@@ -1,4 +1,5 @@
-gdbus_src = gnome.gdbus_codegen('generated-gdbus-no-docbook', 'com.example.Sample.xml',
+gdbus_src = gnome.gdbus_codegen('generated-gdbus-no-docbook',
+  'data/com.example.Sample.xml',
   interface_prefix : 'com.example.',
   namespace : 'Sample',
   annotations : [
@@ -10,7 +11,7 @@ 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')
 
 gdbus_src = gnome.gdbus_codegen('generated-gdbus',
-  sources : 'com.example.Sample.xml',
+  sources : files('data/com.example.Sample.xml'),
   interface_prefix : 'com.example.',
   namespace : 'Sample',
   annotations : [