There are two different kinds of extensions: modules that create new

objects directly and snippets that just call into interpreter methods.

mesonbuild/interpreter.py

@@ -1011,7 +1011,9 @@ class ModuleHolder(InterpreterObject):
         state.build_machine = self.interpreter.builtin['build_machine'].held_object
         state.host_machine = self.interpreter.builtin['host_machine'].held_object
         state.target_machine = self.interpreter.builtin['target_machine'].held_object
-        state.interpreter = self.interpreter
+        if self.held_object.is_snippet(method_name):
+            value = fn(self.interpreter, state, args, kwargs)
+        else:
             value = fn(state, args, kwargs)
             if num_targets != len(self.interpreter.build.targets):
                 raise InterpreterException('Extension module altered internal state illegally.')

mesonbuild/modules/__init__.py

@@ -6,6 +6,13 @@ from ..mesonlib import MesonException
 
 _found_programs = {}
 
+class ExtensionModule:
+    def __init__(self):
+        self.snippets = set() # List of methods that operate only on the interpreter.
+
+    def is_snippet(self, funcname):
+        return funcname in self.snippets
+
 def find_program(program_name, target_name):
     if program_name in _found_programs:
         return _found_programs[program_name]

mesonbuild/modules/gnome.py

@@ -29,6 +29,7 @@ from .. import compilers
 from .. import interpreter
 from . import GResourceTarget, GResourceHeaderTarget, GirTarget, TypelibTarget, VapiTarget
 from . import find_program, get_include_args
+from . import ExtensionModule
 
 
 # gresource compilation is broken due to the way
@@ -57,7 +58,7 @@ def gir_has_extra_lib_arg():
         pass
     return _gir_has_extra_lib_arg
 
-class GnomeModule:
+class GnomeModule(ExtensionModule):
     gir_dep = None
 
     @staticmethod

mesonbuild/modules/i18n.py

@@ -12,13 +12,14 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+import sys
+import shutil
+
 from os import path
 from .. import coredata, mesonlib, build
 from ..mesonlib import MesonException
 from . import ModuleReturnValue
-
-import sys
-import shutil
+from . import ExtensionModule
 
 PRESET_ARGS = {
     'glib': [
@@ -46,7 +47,7 @@ PRESET_ARGS = {
     ]
 }
 
-class I18nModule:
+class I18nModule(ExtensionModule):
 
     def merge_file(self, state, args, kwargs):
         podir = kwargs.pop('po_dir', None)

mesonbuild/modules/modtest.py

@@ -13,8 +13,9 @@
 # limitations under the License.
 
 from . import ModuleReturnValue
+from . import ExtensionModule
 
-class TestModule:
+class TestModule(ExtensionModule):
 
     def print_hello(self, state, args, kwargs):
         print('Hello from a Meson module')

mesonbuild/modules/pkgconfig.py

@@ -12,14 +12,16 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+import os
+
 from .. import build
 from .. import mesonlib
 from .. import mlog
 from . import ModuleReturnValue
+from . import ExtensionModule
 
-import os
 
-class PkgConfigModule:
+class PkgConfigModule(ExtensionModule):
 
     def _get_lname(self, l, msg, pcfile):
         # Nothing special

mesonbuild/modules/python3.py

@@ -12,13 +12,16 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from .. import coredata, build
 from .. import mesonlib
-import os
 
-class Python3Module:
+from . import ExtensionModule
 
-    def extension_module(self, state, args, kwargs):
+class Python3Module(ExtensionModule):
+    def __init__(self):
+        super().__init__()
+        self.snippets.add('extension_module')
+
+    def extension_module(self, interpreter, state, args, kwargs):
         if 'name_prefix' in kwargs:
             raise mesonlib.MesonException('Name_prefix is set automatically, specifying it is forbidden.')
         if 'name_suffix' in kwargs:
@@ -34,7 +37,7 @@ class Python3Module:
             suffix = []
         kwargs['name_prefix'] = ''
         kwargs['name_suffix'] = suffix
-        return state.interpreter.func_shared_module(None, args, kwargs)
+        return interpreter.func_shared_module(None, args, kwargs)
 
 def initialize():
     return Python3Module()

mesonbuild/modules/qt4.py

@@ -17,10 +17,11 @@ from .. import mlog
 from .. import build
 from ..mesonlib import MesonException, Popen_safe
 from ..dependencies import Qt4Dependency
+from . import ExtensionModule
 import xml.etree.ElementTree as ET
 from . import ModuleReturnValue
 
-class Qt4Module():
+class Qt4Module(ExtensionModule):
     tools_detected = False
 
     def _detect_tools(self, env):

mesonbuild/modules/qt5.py

@@ -17,10 +17,11 @@ from .. import mlog
 from .. import build
 from ..mesonlib import MesonException, Popen_safe
 from ..dependencies import Qt5Dependency
+from . import ExtensionModule
 import xml.etree.ElementTree as ET
 from . import ModuleReturnValue
 
-class Qt5Module():
+class Qt5Module(ExtensionModule):
     tools_detected = False
 
     def _detect_tools(self, env):

mesonbuild/modules/rpm.py

@@ -21,10 +21,11 @@ import datetime
 from .. import mlog
 from . import GirTarget, TypelibTarget
 from . import ModuleReturnValue
+from . import ExtensionModule
 
 import os
 
-class RPMModule:
+class RPMModule(ExtensionModule):
 
     def generate_spec_template(self, state, args, kwargs):
         compiler_deps = set()

mesonbuild/modules/windows.py

@@ -12,14 +12,15 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+import os
+
 from .. import mesonlib, dependencies, build
 from ..mesonlib import MesonException
 from . import get_include_args
 from . import ModuleReturnValue
+from . import ExtensionModule
 
-import os
-
-class WindowsModule:
+class WindowsModule(ExtensionModule):
 
     def detect_compiler(self, compilers):
         for l in ('c', 'cpp'):