code: use properties for derived attributes, use slots

Make the objects more light weight.

Remove unused properties.

Author: bluetech

src/_pytest/_code/code.py

@@ -54,14 +54,13 @@
 class Code:
     """Wrapper around Python code objects."""
 
+    __slots__ = ("raw",)
+
     def __init__(self, rawcode) -> None:
         if not hasattr(rawcode, "co_filename"):
             rawcode = getrawcode(rawcode)
         if not isinstance(rawcode, CodeType):
             raise TypeError(f"not a code object: {rawcode!r}")
-        self.filename = rawcode.co_filename
-        self.firstlineno = rawcode.co_firstlineno - 1
-        self.name = rawcode.co_name
         self.raw = rawcode
 
     def __eq__(self, other):
@@ -70,6 +69,14 @@ def __eq__(self, other):
     # Ignore type because of https://github.com/python/mypy/issues/4266.
     __hash__ = None  # type: ignore
 
+    @property
+    def firstlineno(self) -> int:
+        return self.raw.co_firstlineno - 1
+
+    @property
+    def name(self) -> str:
+        return self.raw.co_name
+
     @property
     def path(self) -> Union[py.path.local, str]:
         """Return a path object pointing to source code, or an ``str`` in
@@ -117,12 +124,26 @@ class Frame:
     """Wrapper around a Python frame holding f_locals and f_globals
     in which expressions can be evaluated."""
 
+    __slots__ = ("raw",)
+
     def __init__(self, frame: FrameType) -> None:
-        self.lineno = frame.f_lineno - 1
-        self.f_globals = frame.f_globals
-        self.f_locals = frame.f_locals
         self.raw = frame
-        self.code = Code(frame.f_code)
+
+    @property
+    def lineno(self) -> int:
+        return self.raw.f_lineno - 1
+
+    @property
+    def f_globals(self) -> Dict[str, Any]:
+        return self.raw.f_globals
+
+    @property
+    def f_locals(self) -> Dict[str, Any]:
+        return self.raw.f_locals
+
+    @property
+    def code(self) -> Code:
+        return Code(self.raw.f_code)
 
     @property
     def statement(self) -> "Source":
@@ -164,17 +185,20 @@ def getargs(self, var: bool = False):
 class TracebackEntry:
     """A single entry in a Traceback."""
 
-    _repr_style: Optional['Literal["short", "long"]'] = None
-    exprinfo = None
+    __slots__ = ("_rawentry", "_excinfo", "_repr_style")
 
     def __init__(
         self,
         rawentry: TracebackType,
         excinfo: Optional["ReferenceType[ExceptionInfo[BaseException]]"] = None,
     ) -> None:
-        self._excinfo = excinfo
         self._rawentry = rawentry
-        self.lineno = rawentry.tb_lineno - 1
+        self._excinfo = excinfo
+        self._repr_style: Optional['Literal["short", "long"]'] = None
+
+    @property
+    def lineno(self) -> int:
+        return self._rawentry.tb_lineno - 1
 
     def set_repr_style(self, mode: "Literal['short', 'long']") -> None:
         assert mode in ("short", "long")

testing/code/test_excinfo.py

@@ -747,7 +747,6 @@ def entry():
         from _pytest._code.code import Code
 
         monkeypatch.setattr(Code, "path", "bogus")
-        excinfo.traceback[0].frame.code.path = "bogus"  # type: ignore[misc]
         p = FormattedExcinfo(style="short")
         reprtb = p.repr_traceback_entry(excinfo.traceback[-2])
         lines = reprtb.lines