[Depends on #3701] Add tests for trivial constraints in pyomo/contrib/solver

pyomo/contrib/observer/__init__.py

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+#  ___________________________________________________________________________
+#
+#  Pyomo: Python Optimization Modeling Objects
+#  Copyright (c) 2008-2025
+#  National Technology and Engineering Solutions of Sandia, LLC
+#  Under the terms of Contract DE-NA0003525 with National Technology and
+#  Engineering Solutions of Sandia, LLC, the U.S. Government retains certain
+#  rights in this software.
+#  This software is distributed under the 3-clause BSD License.
+#  ___________________________________________________________________________

pyomo/contrib/observer/component_collector.py

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+#  ___________________________________________________________________________
+#
+#  Pyomo: Python Optimization Modeling Objects
+#  Copyright (c) 2008-2025
+#  National Technology and Engineering Solutions of Sandia, LLC
+#  Under the terms of Contract DE-NA0003525 with National Technology and
+#  Engineering Solutions of Sandia, LLC, the U.S. Government retains certain
+#  rights in this software.
+#  This software is distributed under the 3-clause BSD License.
+#  ___________________________________________________________________________
+
+from pyomo.core.expr.visitor import StreamBasedExpressionVisitor
+from pyomo.core.expr.numeric_expr import (
+    ExternalFunctionExpression,
+    NPV_ExternalFunctionExpression,
+)
+from pyomo.core.base.var import VarData, ScalarVar
+from pyomo.core.base.param import ParamData, ScalarParam
+from pyomo.core.base.expression import ExpressionData, ScalarExpression
+
+
+def handle_var(node, collector):
+    collector.variables[id(node)] = node
+    return None
+
+
+def handle_param(node, collector):
+    collector.params[id(node)] = node
+    return None
+
+
+def handle_named_expression(node, collector):
+    collector.named_expressions[id(node)] = node
+    return None
+
+
+def handle_external_function(node, collector):
+    collector.external_functions[id(node)] = node
+    return None
+
+
+collector_handlers = {
+    VarData: handle_var,
+    ScalarVar: handle_var,
+    ParamData: handle_param,
+    ScalarParam: handle_param,
+    ExpressionData: handle_named_expression,
+    ScalarExpression: handle_named_expression,
+    ExternalFunctionExpression: handle_external_function,
+    NPV_ExternalFunctionExpression: handle_external_function,
+}
+
+
+class _ComponentFromExprCollector(StreamBasedExpressionVisitor):
+    def __init__(self, **kwds):
+        self.named_expressions = {}
+        self.variables = {}
+        self.params = {}
+        self.external_functions = {}
+        super().__init__(**kwds)
+
+    def exitNode(self, node, data):
+        nt = type(node)
+        if nt in collector_handlers:
+            return collector_handlers[nt](node, self)
+        else:
+            return None
+
+
+_visitor = _ComponentFromExprCollector()
+
+
+def collect_components_from_expr(expr):
+    _visitor.__init__()
+    _visitor.walk_expression(expr)
+    return (
+        list(_visitor.named_expressions.values()),
+        list(_visitor.variables.values()),
+        list(_visitor.params.values()),
+        list(_visitor.external_functions.values()),
+    )