subproject handling: add fix

mesonbuild/interpreter.py

@@ -2172,7 +2172,17 @@ to directly access options of other subprojects.''')
             # a higher level project, try to use it first.
             if 'fallback' in kwargs:
                 dirname, varname = self.get_subproject_infos(kwargs)
+                required = kwargs.get('required', True)
+                wanted = kwargs.get('version', 'undefined')
+                if not isinstance(required, bool):
+                    raise DependencyException('Keyword "required" must be a boolean.')
                 if dirname in self.subprojects:
+                    found = self.subprojects[dirname].held_object.project_version
+                    valid_version = wanted == 'undefined' or mesonlib.version_compare(found, wanted)
+                    if required and not valid_version:
+                        m = 'Version {} of {} already loaded, requested incompatible version {}'
+                        raise DependencyException(m.format(found, dirname, wanted))
+                    elif valid_version:
                         subproject = self.subprojects[dirname]
                         try:
                             # Never add fallback deps to self.coredata.deps