1 files changed, 96 insertions, 0 deletions
diff --git a/meson/mesonbuild/interpreterbase/baseobjects.py b/meson/mesonbuild/interpreterbase/baseobjects.py
new file mode 100644
index 000000000..8b1293ca2
--- /dev/null
+++ b/meson/mesonbuild/interpreterbase/baseobjects.py
@@ -0,0 +1,96 @@
+# Copyright 2013-2021 The Meson development team
+
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+
+#     http://www.apache.org/licenses/LICENSE-2.0
+
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from .. import mparser
+from .exceptions import InvalidCode
+from .helpers import flatten, resolve_second_level_holders
+from ..mesonlib import HoldableObject
+
+import typing as T
+
+if T.TYPE_CHECKING:
+    # Object holders need the actual interpreter
+    from ..interpreter import Interpreter
+
+TV_fw_var = T.Union[str, int, bool, list, dict, 'InterpreterObject']
+TV_fw_args = T.List[T.Union[mparser.BaseNode, TV_fw_var]]
+TV_fw_kwargs = T.Dict[str, T.Union[mparser.BaseNode, TV_fw_var]]
+
+TV_func = T.TypeVar('TV_func', bound=T.Callable[..., T.Any])
+
+TYPE_elementary = T.Union[str, int, bool, T.List[T.Any], T.Dict[str, T.Any]]
+TYPE_var = T.Union[TYPE_elementary, HoldableObject, 'MesonInterpreterObject']
+TYPE_nvar = T.Union[TYPE_var, mparser.BaseNode]
+TYPE_kwargs = T.Dict[str, TYPE_var]
+TYPE_nkwargs = T.Dict[str, TYPE_nvar]
+TYPE_key_resolver = T.Callable[[mparser.BaseNode], str]
+
+class InterpreterObject:
+    def __init__(self, *, subproject: T.Optional[str] = None) -> None:
+        self.methods: T.Dict[
+            str,
+            T.Callable[[T.List[TYPE_var], TYPE_kwargs], TYPE_var]
+        ] = {}
+        # Current node set during a method call. This can be used as location
+        # when printing a warning message during a method call.
+        self.current_node:  mparser.BaseNode = None
+        self.subproject: str = subproject or ''
+
+    def method_call(
+                self,
+                method_name: str,
+                args: T.List[TYPE_var],
+                kwargs: TYPE_kwargs
+            ) -> TYPE_var:
+        if method_name in self.methods:
+            method = self.methods[method_name]
+            if not getattr(method, 'no-args-flattening', False):
+                args = flatten(args)
+            if not getattr(method, 'no-second-level-holder-flattening', False):
+                args, kwargs = resolve_second_level_holders(args, kwargs)
+            return method(args, kwargs)
+        raise InvalidCode(f'Unknown method "{method_name}" in object {self} of type {type(self).__name__}.')
+
+class MesonInterpreterObject(InterpreterObject):
+    ''' All non-elementary objects and non-object-holders should be derived from this '''
+
+class MutableInterpreterObject:
+    ''' Dummy class to mark the object type as mutable '''
+
+InterpreterObjectTypeVar = T.TypeVar('InterpreterObjectTypeVar', bound=HoldableObject)
+
+class ObjectHolder(InterpreterObject, T.Generic[InterpreterObjectTypeVar]):
+    def __init__(self, obj: InterpreterObjectTypeVar, interpreter: 'Interpreter') -> None:
+        super().__init__(subproject=interpreter.subproject)
+        assert isinstance(obj, HoldableObject), f'This is a bug: Trying to hold object of type `{type(obj).__name__}` that is not an `HoldableObject`'
+        self.held_object = obj
+        self.interpreter = interpreter
+        self.env = self.interpreter.environment
+
+    def __repr__(self) -> str:
+        return f'<[{type(self).__name__}] holds [{type(self.held_object).__name__}]: {self.held_object!r}>'
+
+class RangeHolder(MesonInterpreterObject):
+    def __init__(self, start: int, stop: int, step: int, *, subproject: str) -> None:
+        super().__init__(subproject=subproject)
+        self.range = range(start, stop, step)
+
+    def __iter__(self) -> T.Iterator[int]:
+        return iter(self.range)
+
+    def __getitem__(self, key: int) -> int:
+        return self.range[key]
+
+    def __len__(self) -> int:
+        return len(self.range)