From 80b86adb66e8159582694ed68896590f1eb8fcdc Mon Sep 17 00:00:00 2001
From: Rahul Savani <rahul.savani@gmail.com>
Date: Mon, 15 Dec 2025 10:19:38 +0000
Subject: [PATCH 1/2] UndefinedOperationError for
 game.player.{actions,infosets} on non-tree

---
 src/pygambit/player.pxi | 21 ++++++++++++++++++++-
 tests/test_strategic.py | 12 ++++++++++++
 2 files changed, 32 insertions(+), 1 deletion(-)

diff --git a/src/pygambit/player.pxi b/src/pygambit/player.pxi
index c68eeeb13..d6f026328 100644
--- a/src/pygambit/player.pxi
+++ b/src/pygambit/player.pxi
@@ -228,15 +228,34 @@ class Player:
            previously, information sets were (expensively) re-sorted after every change
            to the game tree.
 
+        Raises
+        ------
+        UndefinedOperationError
+            If the game does not have a tree representation.
+
         See also
         --------
         Game.sort_infosets
         """
+        if not self.game.is_tree:
+            raise UndefinedOperationError(
+                "Operation only defined for games with a tree representation"
+            )
         return PlayerInfosets.wrap(self.player)
 
     @property
     def actions(self) -> PlayerActions:
-        """Returns the set of actions available to the player at some information set."""
+        """Returns the set of actions available to the player at some information set.
+
+        Raises
+        ------
+        UndefinedOperationError
+            If the game does not have a tree representation.
+        """
+        if not self.game.is_tree:
+            raise UndefinedOperationError(
+                "Operation only defined for games with a tree representation"
+            )
         return PlayerActions.wrap(self)
 
     @property
diff --git a/tests/test_strategic.py b/tests/test_strategic.py
index f1c025509..bba1e0140 100644
--- a/tests/test_strategic.py
+++ b/tests/test_strategic.py
@@ -11,12 +11,24 @@ def test_strategic_game_actions():
         _ = game.actions
 
 
+def test_strategic_game_player_actions():
+    game = gbt.Game.new_table([2, 2])
+    with pytest.raises(gbt.UndefinedOperationError):
+        _ = game.players[0].actions
+
+
 def test_strategic_game_infosets():
     game = gbt.Game.new_table([2, 2])
     with pytest.raises(gbt.UndefinedOperationError):
         _ = game.infosets
 
 
+def test_strategic_game_player_infosets():
+    game = gbt.Game.new_table([2, 2])
+    with pytest.raises(gbt.UndefinedOperationError):
+        _ = game.players[0].infosets
+
+
 def test_strategic_game_root():
     game = gbt.Game.new_table([2, 2])
     with pytest.raises(gbt.UndefinedOperationError):

From 4d26eea51cd518724382ab4df124ae416f61d931 Mon Sep 17 00:00:00 2001
From: Rahul Savani <rahul.savani@gmail.com>
Date: Mon, 15 Dec 2025 15:46:30 +0000
Subject: [PATCH 2/2] UndefinedOperationError for calls to game.nodes and
 game.sort_infosets on non-trees

---
 src/pygambit/game.pxi   | 18 ++++++++++++++++++
 tests/test_strategic.py |  9 ++++++++-
 2 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/src/pygambit/game.pxi b/src/pygambit/game.pxi
index 69ca46587..9654658f7 100644
--- a/src/pygambit/game.pxi
+++ b/src/pygambit/game.pxi
@@ -742,7 +742,16 @@ class Game:
         .. versionchanged:: 16.4
            Changed from a method ``nodes()`` to a property.
 
+        Raises
+        ------
+        UndefinedOperationError
+            If the game does not have a tree representation.
         """
+        if not self.is_tree:
+            raise UndefinedOperationError(
+                "Operation only defined for games with a tree representation"
+            )
+
         return GameNodes.wrap(self.game)
 
     @property
@@ -1885,11 +1894,20 @@ class Game:
 
         .. versionadded:: 16.4.0
 
+        Raises
+        ------
+        UndefinedOperationError
+            If the game does not have a tree representation.
+
         See also
         --------
         Player.infosets
         Infoset.members
         """
+        if not self.is_tree:
+            raise UndefinedOperationError(
+                "Operation only defined for games with a tree representation"
+            )
         self.game.deref().SortInfosets()
 
     def add_player(self, label: str = "") -> Player:
diff --git a/tests/test_strategic.py b/tests/test_strategic.py
index bba1e0140..f6c87e60d 100644
--- a/tests/test_strategic.py
+++ b/tests/test_strategic.py
@@ -37,7 +37,14 @@ def test_strategic_game_root():
 
 def test_strategic_game_nodes():
     game = gbt.Game.new_table([2, 2])
-    assert list(game.nodes) == []
+    with pytest.raises(gbt.UndefinedOperationError):
+        _ = game.nodes
+
+
+def test_strategic_game_sort_infosets():
+    game = gbt.Game.new_table([2, 2])
+    with pytest.raises(gbt.UndefinedOperationError):
+        _ = game.sort_infosets()
 
 
 def test_game_behav_profile_error():