Track variables marked as global in static analysis. This is needed in an upcoming CL.

PiperOrigin-RevId: 288736389
Change-Id: I2c8854d301adeb45e1ca7422b00c455f60d8f7cc

tensorflow/python/autograph/pyct/static_analysis/activity.py

@@ -63,20 +63,18 @@ class Scope(object):
     bound: Set[qual_names.QN], names that are bound to this scope. See
       https://docs.python.org/3/reference/executionmodel.html#binding-of-names
       for a precise definition.
-    free: Set[qual_names.QN], names that are free variables in the context of
-      this scpe. This property only matches Python's notion of free variables
-      for isolated scopes. For example, the scope tracking the body of an if
-      statement will count a variable that it used but not bound as free,
-      even if it's actually bound elsewhere in the enclosing function.
+    globals: Set[qual_names.QN], names that are explicitly marked as global in
+      this scope. Note that this doesn't include free read-only vars bound to
+      global symbols.
+    free_vars: Set[qual_names.QN], the free variables in this scope. See
+      https://docs.python.org/3/reference/executionmodel.html for a precise
+      definition.
     params: WeakValueDictionary[qual_names.QN, ast.Node], function arguments
       visible in this scope, mapped to the function node that defines them.
     enclosing_scope: Scope, the innermost isolated scope that is a transitive
       parent of this scope. May be the scope itself.
     referenced: Set[qual_names.QN], the totality of the symbols used by this
       scope and its parents.
-    free_vars: Set[qual_names.QN], the free variables in this scope. See
-      https://docs.python.org/3/reference/executionmodel.html for a precise
-      definition.
     is_final: bool, whether the scope is frozen or not.
 
   Note - simple statements may never delete and modify a symbol at the same
@@ -106,6 +104,7 @@ class Scope(object):
     self.deleted = set()
 
     self.bound = set()
+    self.globals = set()
 
     self.params = weakref.WeakValueDictionary()
 
@@ -174,6 +173,7 @@ class Scope(object):
         self.parent.read.update(self.read)
         self.parent.modified.update(self.modified)
         self.parent.bound.update(self.bound)
+        self.parent.globals.update(self.globals)
       else:
         # TODO(mdan): This is not accurate.
         self.parent.read.update(self.read - self.bound)
@@ -305,6 +305,11 @@ class ActivityAnalyzer(transformer.Base):
     self._exit_and_record_scope(node)
     return node
 
+  def visit_Global(self, node):
+    for name in node.names:
+      self.scope.globals.add(qual_names.QN(name))
+    return node
+
   def visit_Expr(self, node):
     return self._process_statement(node)
 

tensorflow/python/autograph/pyct/static_analysis/activity_test.py

@@ -541,6 +541,8 @@ class ActivityAnalyzerTest(ActivityAnalyzerTestBase):
     fn_node = node
     body_scope = anno.getanno(fn_node, NodeAnno.BODY_SCOPE)
     self.assertScopeIs(body_scope, ('global_b', 'c'), ('global_a',))
+    self.assertSetEqual(body_scope.globals, set(
+        (QN('global_a'), QN('global_b'))))
 
   def test_class_definition_basic(self):