SCons: Generate header with info on which modules are enabled

We already had `MODULE_*_ENABLED` defines but only in the modules
environment, and a few custom `*_ENABLED` defines in the main env
when we needed the information in core.

Now this is defined in a single header which can be included in the
files that need this information.

(cherry picked from commit b7297fb39c)

core/core_builders.py

@@ -1,8 +1,8 @@
 """Functions used to generate source files during build time
 
 All such functions are invoked in a subprocess on Windows to prevent build flakiness.
-
 """
+
 from platform_methods import subprocess_main
 from compat import iteritems, itervalues, open_utf8, escape_string, byte_to_str
 

methods.py

@@ -238,27 +238,25 @@ def write_modules(modules):
         except IOError:
             pass
 
-    modules_cpp = (
-        """
-// modules.cpp - THIS FILE IS GENERATED, DO NOT EDIT!!!!!!!
+    modules_cpp = """// register_module_types.gen.cpp
+/* THIS FILE IS GENERATED DO NOT EDIT */
 #include "register_module_types.h"
 
-"""
-        + includes_cpp
-        + """
+#include "modules/modules_enabled.gen.h"
+
+%s
 
 void register_module_types() {
-"""
-        + register_cpp
-        + """
+%s
 }
 
 void unregister_module_types() {
-"""
-        + unregister_cpp
-        + """
+%s
 }
-"""
+""" % (
+        includes_cpp,
+        register_cpp,
+        unregister_cpp,
     )
 
     # NOTE: It is safe to generate this file here, since this is still executed serially

modules/SCsub

@@ -4,19 +4,18 @@ Import("env")
 
 import os
 
+import modules_builders
+
 env_modules = env.Clone()
 
 Export("env_modules")
 
-env.modules_sources = []
+env.CommandNoCache("modules_enabled.gen.h", Value(env.module_list), modules_builders.generate_modules_enabled)
 
+env.modules_sources = []
 env_modules.add_source_files(env.modules_sources, "register_module_types.gen.cpp")
 
 for name, path in env.module_list.items():
-    if name in env.disabled_modules:
-        continue
-
-    env_modules.Append(CPPDEFINES=["MODULE_" + name.upper() + "_ENABLED"])
     if not os.path.isabs(path):
         SConscript(name + "/SCsub")  # Built-in.
     else:

modules/modules_builders.py

@@ -0,0 +1,16 @@
+"""Functions used to generate source files during build time
+
+All such functions are invoked in a subprocess on Windows to prevent build flakiness.
+"""
+
+from platform_methods import subprocess_main
+
+
+def generate_modules_enabled(target, source, env):
+    with open(target[0].path, "w") as f:
+        for module in env.module_list:
+            f.write("#define %s\n" % ("MODULE_" + module.upper() + "_ENABLED"))
+
+
+if __name__ == "__main__":
+    subprocess_main(globals())

modules/register_module_types.h

@@ -31,9 +31,7 @@
 #ifndef REGISTER_MODULE_TYPES_H
 #define REGISTER_MODULE_TYPES_H
 
-//
-
 void register_module_types();
 void unregister_module_types();
 
-#endif
+#endif // REGISTER_MODULE_TYPES_H