New semantic analyzer: fix access to imported name in class body (python#6943)

We shouldn't use the line number of an imported name to decide
whether it's defined when the line number refers to another
file.

Author: JukkaL

mypy/build.py

@@ -42,7 +42,9 @@
 from mypy.checker import TypeChecker
 from mypy.indirection import TypeIndirectionVisitor
 from mypy.errors import Errors, CompileError, ErrorInfo, report_internal_error
-from mypy.util import DecodeError, decode_python_encoding, is_sub_path, get_mypy_comments
+from mypy.util import (
+    DecodeError, decode_python_encoding, is_sub_path, get_mypy_comments, module_prefix
+)
 if MYPY:
     from mypy.report import Reports  # Avoid unconditional slow import
 from mypy import moduleinfo
@@ -875,7 +877,7 @@ def invert_deps(deps: Dict[str, Set[str]],
     fake module FAKE_ROOT_MODULE if none are.
     """
     # Lazy import to speed up startup
-    from mypy.server.target import module_prefix, trigger_to_target
+    from mypy.server.target import trigger_to_target
 
     # Prepopulate the map for all the modules that have been processed,
     # so that we always generate files for processed modules (even if

mypy/newsemanal/semanal.py

@@ -99,7 +99,9 @@
     Plugin, ClassDefContext, SemanticAnalyzerPluginInterface,
     DynamicClassDefContext
 )
-from mypy.util import get_prefix, correct_relative_import, unmangle, split_module_names
+from mypy.util import (
+    get_prefix, correct_relative_import, unmangle, module_prefix
+)
 from mypy.scope import Scope
 from mypy.newsemanal.semanal_shared import (
     SemanticAnalyzerInterface, set_callable_name, calculate_tuple_fallback, PRIORITY_FALLBACKS
@@ -3752,20 +3754,7 @@ def lookup(self, name: str, ctx: Context,
         if self.type and not self.is_func_scope() and name in self.type.names:
             node = self.type.names[name]
             if not node.implicit:
-                # Only allow access to class attributes textually after
-                # the definition, so that it's possible to fall back to the
-                # outer scope. Example:
-                #
-                #     class X: ...
-                #
-                #     class C:
-                #         X = X  # Initializer refers to outer scope
-                #
-                # Nested classes are an exception, since we want to support
-                # arbitrary forward references in type annotations.
-                if (node.node is None
-                        or node.node.line < self.statement.line
-                        or isinstance(node.node, TypeInfo)):
+                if self.is_active_symbol_in_class_body(node.node):
                     return node
             else:
                 # Defined through self.x assignment
@@ -3798,6 +3787,33 @@ def lookup(self, name: str, ctx: Context,
                 return implicit_node
         return None
 
+    def is_active_symbol_in_class_body(self, node: Optional[SymbolNode]) -> bool:
+        """Can a symbol defined in class body accessed at current statement?
+
+        Only allow access to class attributes textually after
+        the definition, so that it's possible to fall back to the
+        outer scope. Example:
+
+            class X: ...
+
+            class C:
+                X = X  # Initializer refers to outer scope
+
+        Nested classes are an exception, since we want to support
+        arbitrary forward references in type annotations.
+        """
+        # TODO: Forward reference to name imported in class body is not
+        #       caught.
+        return (node is None
+                or node.line < self.statement.line
+                or not self.is_defined_in_current_module(node.fullname())
+                or isinstance(node, TypeInfo))
+
+    def is_defined_in_current_module(self, fullname: Optional[str]) -> bool:
+        if fullname is None:
+            return False
+        return module_prefix(self.modules, fullname) == self.cur_mod_id
+
     def lookup_qualified(self, name: str, ctx: Context,
                          suppress_errors: bool = False) -> Optional[SymbolTableNode]:
         if '.' not in name:
@@ -4455,7 +4471,7 @@ def attribute_already_defined(self,
 
     def is_local_name(self, name: str) -> bool:
         """Does name look like reference to a definition in the current module?"""
-        return self.cur_mod_id in split_module_names(name) or '.' not in name
+        return self.is_defined_in_current_module(name) or '.' not in name
 
     def fail(self,
              msg: str,

mypy/server/target.py

@@ -1,6 +1,3 @@
-from typing import Iterable, Tuple, List, Optional
-
-
 def trigger_to_target(s: str) -> str:
     assert s[0] == '<'
     # Strip off the angle brackets
@@ -9,22 +6,3 @@ def trigger_to_target(s: str) -> str:
     if s[-1] == ']':
         s = s.split('[')[0]
     return s
-
-
-def module_prefix(modules: Iterable[str], target: str) -> Optional[str]:
-    result = split_target(modules, target)
-    if result is None:
-        return None
-    return result[0]
-
-
-def split_target(modules: Iterable[str], target: str) -> Optional[Tuple[str, str]]:
-    remaining = []  # type: List[str]
-    while True:
-        if target in modules:
-            return target, '.'.join(remaining)
-        components = target.rsplit('.', 1)
-        if len(components) == 1:
-            return None
-        target = components[0]
-        remaining.insert(0, components[1])

mypy/server/update.py

@@ -140,8 +140,9 @@
 from mypy.server.aststrip import strip_target
 from mypy.server.aststripnew import strip_target_new, SavedAttributes
 from mypy.server.deps import get_dependencies_of_target
-from mypy.server.target import module_prefix, split_target, trigger_to_target
+from mypy.server.target import trigger_to_target
 from mypy.server.trigger import make_trigger, WILDCARD_TAG
+from mypy.util import module_prefix, split_target
 from mypy.typestate import TypeState
 
 MYPY = False

mypy/suggestions.py

@@ -38,7 +38,7 @@
     reverse_builtin_aliases,
 )
 from mypy.server.update import FineGrainedBuildManager
-from mypy.server.target import module_prefix, split_target
+from mypy.util import module_prefix, split_target
 from mypy.plugin import Plugin, FunctionContext, MethodContext
 from mypy.traverser import TraverserVisitor
 from mypy.checkexpr import has_any_type

mypy/util.py

@@ -4,7 +4,7 @@
 import re
 import subprocess
 import sys
-from typing import TypeVar, List, Tuple, Optional, Dict, Sequence
+from typing import TypeVar, List, Tuple, Optional, Dict, Sequence, Iterable
 
 MYPY = False
 if MYPY:
@@ -33,6 +33,25 @@ def split_module_names(mod_name: str) -> List[str]:
     return out
 
 
+def module_prefix(modules: Iterable[str], target: str) -> Optional[str]:
+    result = split_target(modules, target)
+    if result is None:
+        return None
+    return result[0]
+
+
+def split_target(modules: Iterable[str], target: str) -> Optional[Tuple[str, str]]:
+    remaining = []  # type: List[str]
+    while True:
+        if target in modules:
+            return target, '.'.join(remaining)
+        components = target.rsplit('.', 1)
+        if len(components) == 1:
+            return None
+        target = components[0]
+        remaining.insert(0, components[1])
+
+
 def short_type(obj: object) -> str:
     """Return the last component of the type name of an object.
 

test-data/unit/check-newsemanal.test

@@ -2407,3 +2407,42 @@ class C:
     def g(self) -> None: pass
 
 reveal_type(C.X)  # E: Revealed type is 'Any'
+
+[case testNewAnalyzerImportedNameUsedInClassBody]
+import m
+
+[file m.py]
+class C:
+    from mm import f
+    @dec(f)
+    def m(self): pass
+
+def dec(f): pass
+[file mm.py]
+# 1 padding to increase line number of 'f'
+# 2 padding
+# 3 padding
+# 4 padding
+# 5 padding
+# 6 padding
+def f(): pass
+
+
+[case testNewAnalyzerImportedNameUsedInClassBody2]
+import m
+
+[file m/__init__.py]
+class C:
+    from m.m import f
+    @dec(f)
+    def m(self): pass
+
+def dec(f): pass
+[file m/m.py]
+# 1 padding to increase line number of 'f'
+# 2 padding
+# 3 padding
+# 4 padding
+# 5 padding
+# 6 padding
+def f(): pass