Make Interpreter object unpicklable as it was being pickled by accident in copies of kwargs.

mesonbuild/interpreter.py

@@ -1308,6 +1308,7 @@ class Interpreter(InterpreterBase):
     def __init__(self, build, backend, subproject='', subdir='', subproject_dir='subprojects',
                  default_project_options=[]):
         super().__init__(build.environment.get_source_dir(), subdir)
+        self.an_unpicklable_object = mesonlib.an_unpicklable_object
         self.build = build
         self.environment = build.environment
         self.coredata = self.environment.get_coredata()

mesonbuild/interpreterbase.py

@@ -61,6 +61,7 @@ class permittedKwargs:
         self.permitted = permitted
 
     def __call__(self, f):
+        @wraps(f)
         def wrapped(s, node, args, kwargs):
             for k in kwargs:
                 if k not in self.permitted:

mesonbuild/mesonlib.py

@@ -21,6 +21,11 @@ import collections
 
 from glob import glob
 
+# Put this in objects that should not get dumped to pickle files
+# by accident.
+import threading
+an_unpicklable_object = threading.Lock()
+
 class MesonException(Exception):
     '''Exceptions thrown by Meson'''