use new variable visitor in get_vars_from_components rather than iden…

…tify_variables_in_expressions

pyomo/core/expr/visitor.py

@@ -1433,40 +1433,6 @@ def acceptChildResult(self, node, data, child_result, child_idx):
         return child_result.is_expression_type(), None
 
 
-def identify_variables_in_components(components, include_fixed=True):
-    visitor = _StreamVariableVisitor(
-        include_fixed=include_fixed, descend_into_named_expressions=False
-    )
-    all_variables = []
-    for comp in components:
-        all_variables.extend(visitor.walk_expressions(comp.expr))
-
-    named_expr_set = set()
-    unique_named_exprs = []
-    for expr in visitor.named_expressions:
-        if id(expr) in named_expr_set:
-            named_expr_set.add(id(expr))
-            unique_named_exprs.append(expr)
-
-    while unique_named_exprs:
-        expr = unique_named_exprs.pop()
-        visitor.named_expressions.clear()
-        all_variables.extend(visitor.walk_expression(expr.expr))
-
-        for new_expr in visitor.named_expressions:
-            if id(new_expr) not in named_expr_set:
-                named_expr_set.add(new_expr)
-                unique_named_exprs.append(new_expr)
-
-    unique_vars = []
-    var_set = set()
-    for var in all_variables:
-        if id(var) not in var_set:
-            var_set.add(id(var))
-            unique_vars.append(var)
-    return unique_vars
-
-
 def identify_variables(expr, include_fixed=True):
     """
     A generator that yields a sequence of variables

pyomo/util/vars_from_expressions.py

@@ -17,7 +17,7 @@
 actually in the subtree or not.
 """
 from pyomo.core import Block
-import pyomo.core.expr as EXPR
+from pyomo.core.expr.visitor import _StreamVariableVisitor
 
 
 def get_vars_from_components(
@@ -42,17 +42,32 @@ def get_vars_from_components(
         descend_into: Ctypes to descend into when finding Constraints
         descent_order: Traversal strategy for finding the objects of type ctype
     """
-    seen = set()
+    visitor = _StreamVariableVisitor(
+        include_fixed=include_fixed, descend_into_named_expressions=False
+    )
+    variables = []
     for constraint in block.component_data_objects(
         ctype,
         active=active,
         sort=sort,
         descend_into=descend_into,
         descent_order=descent_order,
     ):
-        for var in EXPR.identify_variables(
-            constraint.expr, include_fixed=include_fixed
-        ):
-            if id(var) not in seen:
-                seen.add(id(var))
-                yield var
+        variables.extend(visitor.walk_expression(constraint.expr))
+        seen_named_exprs = set()
+        named_expr_stack = list(visitor.named_expressions)
+        while named_expr_stack:
+            expr = named_expr_stack.pop()
+            # Clear visitor's named expression cache so we only identify new
+            # named expressions
+            visitor.named_expressions.clear()
+            variables.extend(visitor.walk_expression(expr.expr))
+            for new_expr in visitor.named_expressions:
+                if id(new_expr) not in seen_named_exprs:
+                    seen_named_exprs.add(id(new_expr))
+                    named_expr_stack.append(new_expr)
+    seen = set()
+    for var in variables:
+        if id(var) not in seen:
+            seen.add(id(var))
+            yield var