Fix star import dependencies in mypy daemon (#21673)

Changes weren't propagated reliably when exporting names using `from
<...> import *`. This could result in false negatives and false
positives.

I used coding agent assist with small incremental changes.

Author: JukkaL

mypy/server/deps.py

@@ -671,6 +671,13 @@ def visit_member_expr(self, e: MemberExpr) -> None:
         if e.kind is not None:
             # Reference to a module attribute
             self.process_global_ref_expr(e)
+            if isinstance(e.expr, RefExpr) and isinstance(e.expr.node, MypyFile):
+                # Also depend on the name as accessed through this module. The
+                # fullname above may point to the original definition (e.g. via
+                # a re-export using "from ... import *"), but we must also
+                # recheck if the name is removed from the accessed module's
+                # namespace.
+                self.add_dependency(make_trigger(e.expr.node.fullname + "." + e.name))
         else:
             # Reference to a non-module (or missing) attribute
             if e.expr not in self.type_map:

mypy/server/update.py

@@ -783,31 +783,37 @@ def calculate_active_triggers(
         else:
             snapshot2 = snapshot_symbol_table(id, new.names)
         diff = compare_symbol_table_snapshots(id, snapshot1, snapshot2)
-        package_nesting_level = id.count(".")
-        for item in diff.copy():
-            if item.count(".") <= package_nesting_level + 1 and item.split(".")[-1] not in (
-                "__builtins__",
-                "__file__",
-                "__name__",
-                "__package__",
-                "__doc__",
-            ):
-                # Activate catch-all wildcard trigger for top-level module changes (used for
-                # "from m import *"). This also gets triggered by changes to module-private
-                # entries, but as these unneeded dependencies only result in extra processing,
-                # it's a minor problem.
-                #
-                # TODO: Some __* names cause mistriggers. Fix the underlying issue instead of
-                #     special casing them here.
-                diff.add(id + WILDCARD_TAG)
-            if item.count(".") > package_nesting_level + 1:
-                # These are for changes within classes, used by protocols.
-                diff.add(item.rsplit(".", 1)[0] + WILDCARD_TAG)
-
+        diff |= wildcard_triggers_for_changes(id, diff)
         names |= diff
     return {make_trigger(name) for name in names}
 
 
+def wildcard_triggers_for_changes(module_id: str, diff: set[str]) -> set[str]:
+    """Return catch-all wildcard triggers activated by a set of changed names."""
+    result: set[str] = set()
+    package_nesting_level = module_id.count(".")
+    for item in diff:
+        if item.count(".") <= package_nesting_level + 1 and item.split(".")[-1] not in (
+            "__builtins__",
+            "__file__",
+            "__name__",
+            "__package__",
+            "__doc__",
+        ):
+            # Activate catch-all wildcard trigger for top-level module changes (used for
+            # "from m import *"). This also gets triggered by changes to module-private
+            # entries, but as these unneeded dependencies only result in extra processing,
+            # it's a minor problem.
+            #
+            # TODO: Some __* names cause mistriggers. Fix the underlying issue instead of
+            #     special casing them here.
+            result.add(module_id + WILDCARD_TAG)
+        if item.count(".") > package_nesting_level + 1:
+            # These are for changes within classes, used by protocols.
+            result.add(item.rsplit(".", 1)[0] + WILDCARD_TAG)
+    return result
+
+
 def replace_modules_with_new_variants(
     manager: BuildManager,
     graph: dict[str, State],
@@ -1044,6 +1050,7 @@ def key(node: FineGrainedDeferredNode) -> int:
     changed = compare_symbol_table_snapshots(
         file_node.fullname, old_symbols_snapshot, new_symbols_snapshot
     )
+    changed |= wildcard_triggers_for_changes(module_id, changed)
     new_triggered = {make_trigger(name) for name in changed}
 
     # Dependencies may have changed.

test-data/unit/deps.test

@@ -69,6 +69,19 @@ x = 1
 <n.x> -> m.f
 <n> -> m, m.f
 
+[case testAccessReexportedModuleAttribute]
+import pkg
+pkg.f()
+[file pkg/__init__.py]
+from pkg.sub import *
+[file pkg/sub.py]
+def f() -> None: pass
+[out]
+<pkg.f> -> m
+<pkg.sub.f> -> m
+<pkg.sub[wildcard]> -> pkg
+<pkg> -> m
+
 [case testImport]
 import n
 [file n.py]

test-data/unit/fine-grained.test

@@ -11839,3 +11839,134 @@ def bar() -> str: return "a"
 main:2: note: Revealed type is "None | builtins.int"
 ==
 main:2: note: Revealed type is "None | builtins.str"
+
+[case testStarExportedNameDeleted1]
+import pkg
+
+pkg.loads()
+
+[file pkg/__init__.pyi]
+from .sub import *
+
+[file pkg/sub.pyi]
+def loads() -> None: ...
+
+[file pkg/sub.pyi.2]
+[out]
+==
+main:3: error: "object" has no attribute "loads"
+
+[case testStarExportedNameDeleted2]
+import pkg
+
+pkg.C()
+
+[file pkg/__init__.pyi]
+from .sub import *
+
+[file pkg/sub.pyi]
+class C: pass
+
+[file pkg/sub.pyi.2]
+[out]
+==
+main:3: error: "object" has no attribute "C"
+
+[case testStarExportedNameDeleted3]
+from pkg import loads
+
+loads()
+
+[file pkg/__init__.pyi]
+from .sub import *
+
+[file pkg/sub.pyi]
+def loads() -> None: ...
+
+[file pkg/sub.pyi.2]
+[out]
+==
+main:1: error: Module "pkg" has no attribute "loads"
+
+[case testStarExportedNameDeleted4]
+from pkg import sub
+
+a = sub.x
+
+[file pkg/__init__.pyi]
+from .sub import *
+
+[file pkg/sub.pyi]
+x = 1
+
+[file pkg/sub.pyi.2]
+[out]
+==
+main:3: error: "object" has no attribute "x"
+
+[case testStarExportedNameDeleted5]
+from pkg import sub
+
+x: sub.N = 1
+
+[file pkg/__init__.pyi]
+from .sub import *
+
+[file pkg/sub.pyi]
+N = int
+
+[file pkg/sub.pyi.2]
+[out]
+==
+main:3: error: Name "sub.N" is not defined
+
+[case testStarExportedNameDeleted6]
+from pkg import *
+
+loads()
+
+[file pkg/__init__.pyi]
+from .sub import *
+
+[file pkg/sub.pyi]
+def loads() -> None: ...
+
+[file pkg/sub.pyi.2]
+[out]
+==
+main:3: error: Name "loads" is not defined
+
+[case testStarExportedNameDeleted7]
+from pkg import *
+
+C()
+
+[file pkg/__init__.pyi]
+from .sub import *
+
+[file pkg/sub.pyi]
+class C: pass
+
+[file pkg/sub.pyi.2]
+[out]
+==
+main:3: error: Name "C" is not defined
+
+[case testStarExportedNameDeleted8]
+from a import *
+
+C()
+
+[file a.py]
+from b import *
+
+[file b.py]
+from c import *
+
+[file c.py]
+class C: pass
+
+[file c.py.2]
+[out]
+==
+main:3: error: Name "C" is not defined