Make constants have synthetic root as their parent (#2602)

that fixes a bunch of tests in pylint.

We also make the synthetic root a singleton, as opposed to a module
   built in the astroid manager. That allows us to use it as a default
   value in Const constructors.

ChangeLog

@@ -10,6 +10,8 @@ Release date: TBA
 * Removed internal functions ``infer_numpy_member``, ``name_looks_like_numpy_member``, and
   ``attribute_looks_like_numpy_member`` from ``astroid.brain.brain_numpy_utils``.
 
+* Constants now have a parent of ``nodes.SYNTHETIC_ROOT``.
+
 * Fix crashes with large positive and negative list multipliers.
 
   Closes #2521

astroid/brain/brain_argparse.py

@@ -21,7 +21,7 @@ def infer_namespace(node, context: InferenceContext | None = None):
         "Namespace",
         lineno=node.lineno,
         col_offset=node.col_offset,
-        parent=AstroidManager().synthetic_root,  # this class is not real
+        parent=nodes.SYNTHETIC_ROOT,  # this class is not real
         end_lineno=node.end_lineno,
         end_col_offset=node.end_col_offset,
     )

astroid/brain/brain_builtin_inference.py

@@ -24,7 +24,6 @@
 from astroid.inference_tip import inference_tip
 from astroid.manager import AstroidManager
 from astroid.nodes import scoped_nodes
-from astroid.raw_building import build_module
 from astroid.typing import (
     ConstFactoryResult,
     InferenceResult,
@@ -165,8 +164,6 @@ def _extend_builtins(class_transforms):
 
 def on_bootstrap():
     """Called by astroid_bootstrapping()."""
-    AstroidManager().cache_module(build_module("__astroid_synthetic"))
-
     _extend_builtins(
         {
             "bytes": partial(_extend_string_class, code=BYTES_CLASS, rvalue="b''"),
@@ -653,7 +650,7 @@ def infer_property(
         # node.frame. It's somewhere in the builtins module, but we are special
         # casing it for each "property()" call, so we are making up the
         # definition on the spot, ad-hoc.
-        parent=AstroidManager().synthetic_root,
+        parent=scoped_nodes.SYNTHETIC_ROOT,
     )
     prop_func.postinit(
         body=[],

astroid/brain/brain_namedtuple_enum.py

@@ -24,6 +24,7 @@
 )
 from astroid.inference_tip import inference_tip
 from astroid.manager import AstroidManager
+from astroid.nodes.scoped_nodes.scoped_nodes import SYNTHETIC_ROOT
 
 ENUM_QNAME: Final[str] = "enum.Enum"
 TYPING_NAMEDTUPLE_QUALIFIED: Final = {
@@ -194,7 +195,7 @@ def infer_named_tuple(
     """Specific inference function for namedtuple Call node."""
     tuple_base: nodes.Name = _extract_single_node("tuple")
     class_node, name, attributes = infer_func_form(
-        node, tuple_base, parent=AstroidManager().synthetic_root, context=context
+        node, tuple_base, parent=SYNTHETIC_ROOT, context=context
     )
 
     call_site = arguments.CallSite.from_call(node, context=context)
@@ -360,7 +361,7 @@ def value(self):
     class_node = infer_func_form(
         node,
         enum_meta,
-        parent=AstroidManager().synthetic_root,
+        parent=SYNTHETIC_ROOT,
         context=context,
         enum=True,
     )[0]

astroid/manager.py

@@ -115,10 +115,6 @@ def unregister_transform(self):
     def builtins_module(self) -> nodes.Module:
         return self.astroid_cache["builtins"]
 
-    @property
-    def synthetic_root(self) -> nodes.Module:
-        return self.astroid_cache["__astroid_synthetic"]
-
     @property
     def prefer_stubs(self) -> bool:
         return AstroidManager.brain["prefer_stubs"]

astroid/nodes/__init__.py

@@ -93,6 +93,7 @@
     unpack_infer,
 )
 from astroid.nodes.scoped_nodes import (
+    SYNTHETIC_ROOT,
     AsyncFunctionDef,
     ClassDef,
     ComprehensionScope,
@@ -276,6 +277,7 @@
     "Position",
     "Raise",
     "Return",
+    "SYNTHETIC_ROOT",
     "Set",
     "SetComp",
     "Slice",

astroid/nodes/node_classes.py

@@ -46,6 +46,7 @@
 from astroid.nodes import _base_nodes
 from astroid.nodes.const import OP_PRECEDENCE
 from astroid.nodes.node_ng import NodeNG
+from astroid.nodes.scoped_nodes import SYNTHETIC_ROOT
 from astroid.typing import (
     ConstFactoryResult,
     InferenceErrorInfo,
@@ -2038,7 +2039,7 @@ def __init__(
         value: Any,
         lineno: int | None = None,
         col_offset: int | None = None,
-        parent: NodeNG | None = None,
+        parent: NodeNG = SYNTHETIC_ROOT,
         kind: str | None = None,
         *,
         end_lineno: int | None = None,
@@ -2550,7 +2551,7 @@ def __init__(
         self,
         lineno: None = None,
         col_offset: None = None,
-        parent: None = None,
+        parent: NodeNG = SYNTHETIC_ROOT,
         *,
         end_lineno: None = None,
         end_col_offset: None = None,
@@ -5535,7 +5536,7 @@ def const_factory(value: Any) -> ConstFactoryResult:
         instance = initializer_cls(
             lineno=None,
             col_offset=None,
-            parent=None,
+            parent=SYNTHETIC_ROOT,
             end_lineno=None,
             end_col_offset=None,
         )
@@ -5545,7 +5546,7 @@ def const_factory(value: Any) -> ConstFactoryResult:
         instance = initializer_cls(
             lineno=None,
             col_offset=None,
-            parent=None,
+            parent=SYNTHETIC_ROOT,
             end_lineno=None,
             end_col_offset=None,
         )

astroid/nodes/scoped_nodes/__init__.py

@@ -11,6 +11,7 @@
 
 from astroid.nodes.scoped_nodes.mixin import ComprehensionScope, LocalsDictNodeNG
 from astroid.nodes.scoped_nodes.scoped_nodes import (
+    SYNTHETIC_ROOT,
     AsyncFunctionDef,
     ClassDef,
     DictComp,
@@ -37,6 +38,7 @@
     "ListComp",
     "LocalsDictNodeNG",
     "Module",
+    "SYNTHETIC_ROOT",
     "SetComp",
     "builtin_lookup",
     "function_to_method",

astroid/nodes/scoped_nodes/scoped_nodes.py

@@ -40,14 +40,7 @@
 from astroid.interpreter.dunder_lookup import lookup
 from astroid.interpreter.objectmodel import ClassModel, FunctionModel, ModuleModel
 from astroid.manager import AstroidManager
-from astroid.nodes import (
-    Arguments,
-    Const,
-    NodeNG,
-    _base_nodes,
-    const_factory,
-    node_classes,
-)
+from astroid.nodes import _base_nodes, node_classes
 from astroid.nodes.scoped_nodes.mixin import ComprehensionScope, LocalsDictNodeNG
 from astroid.nodes.scoped_nodes.utils import builtin_lookup
 from astroid.nodes.utils import Position
@@ -60,6 +53,7 @@
 
 if TYPE_CHECKING:
     from astroid import nodes, objects
+    from astroid.nodes import Arguments, Const, NodeNG
     from astroid.nodes._base_nodes import LookupMixIn
 
 
@@ -177,6 +171,15 @@ def function_to_method(n, klass):
     return n
 
 
+def _infer_last(
+    arg: SuccessfulInferenceResult, context: InferenceContext
+) -> InferenceResult:
+    res = util.Uninferable
+    for b in arg.infer(context=context.clone()):
+        res = b
+    return res
+
+
 class Module(LocalsDictNodeNG):
     """Class representing an :class:`ast.Module` node.
 
@@ -353,7 +356,7 @@ def getattr(
         if name in self.special_attributes and not ignore_locals and not name_in_locals:
             result = [self.special_attributes.lookup(name)]
             if name == "__name__":
-                main_const = const_factory("__main__")
+                main_const = node_classes.const_factory("__main__")
                 main_const.parent = AstroidManager().builtins_module
                 result.append(main_const)
         elif not ignore_locals and name_in_locals:
@@ -607,6 +610,14 @@ def _infer(
         yield self
 
 
+class __SyntheticRoot(Module):
+    def __init__(self):
+        super().__init__("__astroid_synthetic", pure_python=False)
+
+
+SYNTHETIC_ROOT = __SyntheticRoot()
+
+
 class GeneratorExp(ComprehensionScope):
     """Class representing an :class:`ast.GeneratorExp` node.
 
@@ -1538,10 +1549,7 @@ def infer_yield_result(self, context: InferenceContext | None = None):
         """
         for yield_ in self.nodes_of_class(node_classes.Yield):
             if yield_.value is None:
-                const = node_classes.Const(None)
-                const.parent = yield_
-                const.lineno = yield_.lineno
-                yield const
+                yield node_classes.Const(None, parent=yield_, lineno=yield_.lineno)
             elif yield_.scope() == self:
                 yield from yield_.value.infer(context=context)
 
@@ -1551,6 +1559,8 @@ def infer_call_result(
         context: InferenceContext | None = None,
     ) -> Iterator[InferenceResult]:
         """Infer what the function returns when called."""
+        if context is None:
+            context = InferenceContext()
         if self.is_generator():
             if isinstance(self, AsyncFunctionDef):
                 generator_cls: type[bases.Generator] = bases.AsyncGenerator
@@ -1572,7 +1582,7 @@ def infer_call_result(
             and len(self.args.args) == 1
             and self.args.vararg is not None
         ):
-            if isinstance(caller.args, Arguments):
+            if isinstance(caller.args, node_classes.Arguments):
                 assert caller.args.args is not None
                 metaclass = next(caller.args.args[0].infer(context), None)
             elif isinstance(caller.args, list):
@@ -1582,27 +1592,14 @@ def infer_call_result(
                     f"caller.args was neither Arguments nor list; got {type(caller.args)}"
                 )
             if isinstance(metaclass, ClassDef):
-                try:
-                    class_bases = [
-                        # Find the first non-None inferred base value
-                        next(
-                            b
-                            for b in arg.infer(
-                                context=context.clone() if context else context
-                            )
-                            if not (isinstance(b, Const) and b.value is None)
-                        )
-                        for arg in caller.args[1:]
-                    ]
-                except StopIteration as e:
-                    raise InferenceError(node=caller.args[1:], context=context) from e
+                class_bases = [_infer_last(x, context) for x in caller.args[1:]]
                 new_class = ClassDef(
                     name="temporary_class",
                     lineno=0,
                     col_offset=0,
                     end_lineno=0,
                     end_col_offset=0,
-                    parent=AstroidManager().synthetic_root,
+                    parent=SYNTHETIC_ROOT,
                 )
                 new_class.hide = True
                 new_class.postinit(
@@ -2827,13 +2824,8 @@ def _inferred_bases(self, context: InferenceContext | None = None):
 
         for stmt in self.bases:
             try:
-                # Find the first non-None inferred base value
-                baseobj = next(
-                    b
-                    for b in stmt.infer(context=context.clone())
-                    if not (isinstance(b, Const) and b.value is None)
-                )
-            except (InferenceError, StopIteration):
+                baseobj = _infer_last(stmt, context)
+            except InferenceError:
                 continue
             if isinstance(baseobj, bases.Instance):
                 baseobj = baseobj._proxied

astroid/objects.py

@@ -279,7 +279,7 @@ def __init__(self, call, name=None, lineno=None, col_offset=None, parent=None):
             name,
             lineno=lineno,
             col_offset=col_offset,
-            parent=AstroidManager().synthetic_root,
+            parent=scoped_nodes.SYNTHETIC_ROOT,
             end_col_offset=0,
             end_lineno=0,
         )

tests/test_nodes.py

@@ -34,10 +34,8 @@
     AstroidBuildingError,
     AstroidSyntaxError,
     AttributeInferenceError,
-    ParentMissingError,
     StatementMissing,
 )
-from astroid.manager import AstroidManager
 from astroid.nodes.node_classes import (
     AssignAttr,
     AssignName,
@@ -46,7 +44,13 @@
     ImportFrom,
     Tuple,
 )
-from astroid.nodes.scoped_nodes import ClassDef, FunctionDef, GeneratorExp, Module
+from astroid.nodes.scoped_nodes import (
+    SYNTHETIC_ROOT,
+    ClassDef,
+    FunctionDef,
+    GeneratorExp,
+    Module,
+)
 from tests.testdata.python3.recursion_error import LONG_CHAINED_METHOD_CALL
 
 from . import resources
@@ -623,12 +627,10 @@ def _test(self, value: Any) -> None:
         with self.assertRaises(StatementMissing):
             node.statement()
 
-        with self.assertRaises(ParentMissingError):
-            with pytest.warns(DeprecationWarning) as records:
-                node.frame(future=True)
-                assert len(records) == 1
-        with self.assertRaises(ParentMissingError):
-            node.frame()
+        with pytest.warns(DeprecationWarning) as records:
+            assert node.frame(future=True) is SYNTHETIC_ROOT
+            assert len(records) == 1
+        assert node.frame() is SYNTHETIC_ROOT
 
     def test_none(self) -> None:
         self._test(None)
@@ -1962,7 +1964,7 @@ def test_str_repr_no_warnings(node):
             continue
 
         if name == "parent" and "NodeNG" in param_type.annotation:
-            args[name] = AstroidManager().synthetic_root
+            args[name] = SYNTHETIC_ROOT
         elif "int" in param_type.annotation:
             args[name] = random.randint(0, 50)
         elif (

tests/test_regrtest.py

@@ -248,7 +248,7 @@ def with_metaclass(meta, *bases):
             class metaclass(meta):
                 def __new__(cls, name, this_bases, d):
                     return meta(name, bases, d)
-        return type.__new__(metaclass, 'temporary_class', (), {})
+            return type.__new__(metaclass, 'temporary_class', (), {})
 
         import lala