From aca180ae89c76dbf993e45eb2ab500e4fce976fc Mon Sep 17 00:00:00 2001
From: Erik Welch <erik.n.welch@gmail.com>
Date: Thu, 28 Jul 2022 06:54:42 -0500
Subject: [PATCH] Change default return type `PropertyGraph.extract_subgraph()
 -> cugraph.Graph(directed=True)` (#2460)

Fixes #2459

The tests already specify the use of directed graphs most places, so this required minimal changes.

Authors:
  - Erik Welch (https://github.com/eriknw)

Approvers:
  - Rick Ratzel (https://github.com/rlratzel)

URL: https://github.com/rapidsai/cugraph/pull/2460
---
 .../cugraph/dask/structure/mg_property_graph.py      | 12 +++++++++---
 python/cugraph/cugraph/structure/property_graph.py   | 11 ++++++++---
 python/cugraph/cugraph/tests/test_property_graph.py  |  1 +
 3 files changed, 18 insertions(+), 6 deletions(-)

diff --git a/python/cugraph/cugraph/dask/structure/mg_property_graph.py b/python/cugraph/cugraph/dask/structure/mg_property_graph.py
index 9a9438a018e..5b064a49c04 100644
--- a/python/cugraph/cugraph/dask/structure/mg_property_graph.py
+++ b/python/cugraph/cugraph/dask/structure/mg_property_graph.py
@@ -480,7 +480,7 @@ def select_edges(self, expr):
             edge_selection_series=selected_col)
 
     def extract_subgraph(self,
-                         create_using=cugraph.Graph,
+                         create_using=None,
                          selection=None,
                          edge_weight_property=None,
                          default_edge_weight=None,
@@ -494,12 +494,12 @@ def extract_subgraph(self,
 
         Parameters
         ----------
-        create_using : cugraph Graph type or instance
+        create_using : cugraph Graph type or instance, optional
             Creates a Graph to return using the type specified. If an instance
             is specified, the type of the instance is used to construct the
             return Graph, and all relevant attributes set on the instance are
             copied to the return Graph (eg. directed). If not specified the
-            returned Graph will be a cugraph.Graph instance.
+            returned Graph will be a directed cugraph.Graph instance.
         selection : PropertySelection
             A PropertySelection returned from one or more calls to
             select_vertices() and/or select_edges(), used for creating a Graph
@@ -576,6 +576,12 @@ def extract_subgraph(self,
         # values. Restore the original dtypes in the resulting edges df prior
         # to creating a Graph.
         self.__update_dataframe_dtypes(edges, self.__edge_prop_dtypes)
+
+        # Default create_using set here instead of function signature to
+        # prevent cugraph from running on import. This may help diagnose errors
+        if create_using is None:
+            create_using = cugraph.Graph(directed=True)
+
         return self.edge_props_to_graph(
             edges,
             create_using=create_using,
diff --git a/python/cugraph/cugraph/structure/property_graph.py b/python/cugraph/cugraph/structure/property_graph.py
index 59f66f44f93..f5d2cac8823 100644
--- a/python/cugraph/cugraph/structure/property_graph.py
+++ b/python/cugraph/cugraph/structure/property_graph.py
@@ -563,7 +563,7 @@ def select_edges(self, expr):
             edge_selection_series=selected_col)
 
     def extract_subgraph(self,
-                         create_using=cugraph.Graph,
+                         create_using=None,
                          selection=None,
                          edge_weight_property=None,
                          default_edge_weight=None,
@@ -577,12 +577,12 @@ def extract_subgraph(self,
 
         Parameters
         ----------
-        create_using : cugraph Graph type or instance
+        create_using : cugraph Graph type or instance, optional
             Creates a Graph to return using the type specified. If an instance
             is specified, the type of the instance is used to construct the
             return Graph, and all relevant attributes set on the instance are
             copied to the return Graph (eg. directed). If not specified the
-            returned Graph will be a cugraph.Graph instance.
+            returned Graph will be a directed cugraph.Graph instance.
         selection : PropertySelection
             A PropertySelection returned from one or more calls to
             select_vertices() and/or select_edges(), used for creating a Graph
@@ -661,6 +661,11 @@ def extract_subgraph(self,
         # to creating a Graph.
         edges = self.__update_dataframe_dtypes(edges, self.__edge_prop_dtypes)
 
+        # Default create_using set here instead of function signature to
+        # prevent cugraph from running on import. This may help diagnose errors
+        if create_using is None:
+            create_using = cugraph.Graph(directed=True)
+
         return self.edge_props_to_graph(
             edges,
             create_using=create_using,
diff --git a/python/cugraph/cugraph/tests/test_property_graph.py b/python/cugraph/cugraph/tests/test_property_graph.py
index 5a91d9d577f..a85f8df25fe 100644
--- a/python/cugraph/cugraph/tests/test_property_graph.py
+++ b/python/cugraph/cugraph/tests/test_property_graph.py
@@ -755,6 +755,7 @@ def test_extract_subgraph_no_edges(dataset1_PropertyGraph):
 
     selection = pG.select_vertices("(_TYPE_=='merchants') & (merchant_id==86)")
     G = pG.extract_subgraph(selection=selection)
+    assert G.is_directed()
 
     assert len(G.edgelist.edgelist_df) == 0