Fix handling of pos node attribute in to_agraph (#6474)

Make sure the `"pos"` node attribute is properly formatted for pygraphviz,
if present.

2 files changed, 19 insertions, 0 deletions

diff --git a/networkx/drawing/nx_agraph.py b/networkx/drawing/nx_agraph.py
index 2ffa21fd..9a29fab5 100644
--- a/networkx/drawing/nx_agraph.py
+++ b/networkx/drawing/nx_agraph.py
@@ -137,6 +137,13 @@ def to_agraph(N):
         ) from err
     directed = N.is_directed()
     strict = nx.number_of_selfloops(N) == 0 and not N.is_multigraph()
+
+    for node in N:
+        if "pos" in N.nodes[node]:
+            N.nodes[node]["pos"] = "{},{}!".format(
+                N.nodes[node]["pos"][0], N.nodes[node]["pos"][1]
+            )
+
     A = pygraphviz.AGraph(name=N.name, strict=strict, directed=directed)
 
     # default graph attributes
diff --git a/networkx/drawing/tests/test_agraph.py b/networkx/drawing/tests/test_agraph.py
index c99d29fb..1ade719b 100644
--- a/networkx/drawing/tests/test_agraph.py
+++ b/networkx/drawing/tests/test_agraph.py
@@ -240,3 +240,15 @@ class TestAGraph:
         pos = list(pos.values())
         assert len(pos) == 5
         assert len(pos[0]) == 3
+
+    def test_no_warnings_raised(self):
+        # Test that no warnings are raised when Networkx graph
+        # is converted to Pygraphviz graph and 'pos'
+        # attribute is given
+        G = nx.Graph()
+        G.add_node(0, pos=(0, 0))
+        G.add_node(1, pos=(1, 1))
+        A = nx.nx_agraph.to_agraph(G)
+        with pytest.warns(None) as record:
+            A.layout()
+        assert len(record) == 0