stubtest: Improve heuristics for determining whether global-namespace…

… names are imported (#14270)

Stubtest currently has both false-positives and false-negatives when it
comes to verifying constants in the global namespace of a module.

This PR fixes the false positive by using `inspect.getsourcelines()` to
dynamically retrieve the module source code. It then uses `symtable` to
analyse that source code to gather a list of names which are known to be
imported.

The PR fixes the false negative by only using the `__module__` heuristic
on objects which are callable. The vast majority of callable objects
will be types or functions. For these objects, the `__module__`
attribute will give a good indication of whether the object originates
from another module or not; for other objects, it's less useful.

mypy/stubtest.py

@@ -15,6 +15,7 @@
 import os
 import pkgutil
 import re
+import symtable
 import sys
 import traceback
 import types
@@ -283,6 +284,36 @@ def _verify_exported_names(
     )
 
 
+def _get_imported_symbol_names(runtime: types.ModuleType) -> frozenset[str] | None:
+    """Retrieve the names in the global namespace which are known to be imported.
+
+    1). Use inspect to retrieve the source code of the module
+    2). Use symtable to parse the source and retrieve names that are known to be imported
+        from other modules.
+
+    If either of the above steps fails, return `None`.
+
+    Note that if a set of names is returned,
+    it won't include names imported via `from foo import *` imports.
+    """
+    try:
+        source = inspect.getsource(runtime)
+    except (OSError, TypeError, SyntaxError):
+        return None
+
+    if not source.strip():
+        # The source code for the module was an empty file,
+        # no point in parsing it with symtable
+        return frozenset()
+
+    try:
+        module_symtable = symtable.symtable(source, runtime.__name__, "exec")
+    except SyntaxError:
+        return None
+
+    return frozenset(sym.get_name() for sym in module_symtable.get_symbols() if sym.is_imported())
+
+
 @verify.register(nodes.MypyFile)
 def verify_mypyfile(
     stub: nodes.MypyFile, runtime: MaybeMissing[types.ModuleType], object_path: list[str]
@@ -312,15 +343,22 @@ def verify_mypyfile(
         if not o.module_hidden and (not is_probably_private(m) or hasattr(runtime, m))
     }
 
+    imported_symbols = _get_imported_symbol_names(runtime)
+
     def _belongs_to_runtime(r: types.ModuleType, attr: str) -> bool:
         obj = getattr(r, attr)
-        try:
-            obj_mod = getattr(obj, "__module__", None)
-        except Exception:
+        if isinstance(obj, types.ModuleType):
             return False
-        if obj_mod is not None:
-            return bool(obj_mod == r.__name__)
-        return not isinstance(obj, types.ModuleType)
+        if callable(obj):
+            try:
+                obj_mod = getattr(obj, "__module__", None)
+            except Exception:
+                return False
+            if obj_mod is not None:
+                return bool(obj_mod == r.__name__)
+        if imported_symbols is not None:
+            return attr not in imported_symbols
+        return True
 
     runtime_public_contents = (
         runtime_all_as_set

mypy/test/teststubtest.py

@@ -1082,6 +1082,9 @@ def test_missing_no_runtime_all(self) -> Iterator[Case]:
         yield Case(stub="", runtime="import sys", error=None)
         yield Case(stub="", runtime="def g(): ...", error="g")
         yield Case(stub="", runtime="CONSTANT = 0", error="CONSTANT")
+        yield Case(stub="", runtime="import re; constant = re.compile('foo')", error="constant")
+        yield Case(stub="", runtime="from json.scanner import NUMBER_RE", error=None)
+        yield Case(stub="", runtime="from string import ascii_letters", error=None)
 
     @collect_cases
     def test_non_public_1(self) -> Iterator[Case]: