cmake: Handle disabling subprojects

mesonbuild/modules/cmake.py

@@ -274,7 +274,10 @@ class CmakeModule(ExtensionModule):
         if len(args) != 1:
             raise InterpreterException('Subproject takes exactly one argument')
         dirname = args[0]
-        return CMakeSubprojectHolder(interpreter.do_subproject(dirname, 'cmake', kwargs), dirname)
+        subp = interpreter.do_subproject(dirname, 'cmake', kwargs)
+        if not subp.held_object:
+            return subp
+        return CMakeSubprojectHolder(subp, dirname)
 
 def initialize(*args, **kwargs):
     return CmakeModule(*args, **kwargs)

test cases/cmake/9 disabled subproject/meson.build

@@ -0,0 +1,5 @@
+project('cmakeSubTest', ['c', 'cpp'])
+
+cm = import('cmake')
+
+sub_pro = cm.subproject('nothinig', required: false)