Persist modules so they are imported only once for the lifetime of a build directory.

build.py

@@ -74,7 +74,6 @@ class Build:
         self.pkgconfig_gens = []
         self.install_script = None
         self.install_dirs = []
-        self.modules = {}
 
     def has_language(self, language):
         for i in self.compilers:

coredata.py

@@ -54,6 +54,7 @@ class CoreData():
         self.deps = {}
         self.ext_progs = {}
         self.ext_libs = {}
+        self.modules = {}
 
     def get_builtin_option(self, optname):
         if optname == 'type':

interpreter.py

@@ -600,15 +600,15 @@ class ModuleState:
     pass
 
 class ModuleHolder(InterpreterObject):
-    def __init__(self, modname, interpreter):
+    def __init__(self, modname, module, interpreter):
         InterpreterObject.__init__(self)
         self.modname = modname
-        self.m = importlib.import_module('modules.' + modname).initialize()
+        self.held_object = module
         self.interpreter = interpreter
 
     def method_call(self, method_name, args, kwargs):
         try:
-            fn = getattr(self.m, method_name)
+            fn = getattr(self.held_object, method_name)
         except AttributeError:
             raise InvalidArguments('Module %s does not have method %s.' % (self.modname, method_name))
         state = ModuleState()
@@ -735,7 +735,6 @@ class Interpreter():
         self.global_args_frozen = False
         self.subprojects = {}
         self.subproject_stack = []
-        self.modules = {}
 
     def build_func_dict(self):
         self.funcs = {'project' : self.func_project,
@@ -865,11 +864,10 @@ class Interpreter():
         modname = args[0]
         if not isinstance(modname, str):
             raise InvalidCode('Argument to import was not a string')
-        if not modname in self.modules:
-            mh = mh = ModuleHolder(modname, self)
-            self.modules[modname] = mh
-            self.build.modules[modname] = mh.m
-        return self.modules[modname]
+        if not modname in self.environment.coredata.modules:
+            module = importlib.import_module('modules.' + modname).initialize()
+            self.environment.coredata.modules[modname] = module
+        return ModuleHolder(modname, self.environment.coredata.modules[modname], self)
 
     def set_variable(self, varname, variable):
         if variable is None:

test cases/frameworks/4 qt5/meson.build

@@ -10,7 +10,7 @@ endif
 q5exe = executable('qt5app',
 sources : ['main.cpp', 'mainWindow.cpp', # Sources that don't need preprocessing.
 qt5.preprocess(moc_headers : ['mainWindow.h'],           # These need to be fed through the moc tool before use. 
-	                         ui_files : 'mainWindow.ui', # XML files that need to be compiled with the uic tol.
+                             ui_files : 'mainWindow.ui', # XML files that need to be compiled with the uic tol.
                              qresources : 'stuff.qrc',   # Resource file for rcc compiler.
 )],
 dependencies : qt5dep)