Fix Node Wrangler issues with texturecan texture imports

Before this change, if you tried to "Add Principled Setup" for some
texturecan.com materials, Node Wrangler used e.g.
`metal_0010_normal_directx_1k.png` for the normal map.

However Blender wants OpenGL style normal maps. With this change it
now correctly picks `metal_0010_normal_opengl_1k.png`.

Additionally, this change adds a (very) short README with instructions
for how to run the Node Wrangler tests.

Pull Request #104445

node_wrangler/README.md

@@ -0,0 +1,5 @@
+# Running Tests
+
+```
+./util_test.py
+```

node_wrangler/util.py

@@ -153,10 +153,13 @@ def match_files_to_socket_names(files, sockets):
 
     for sname in sockets:
         for name, tag_list in names_to_tag_lists.items():
-            if sname[0] == "Normal" and "dx" in tag_list:
+            if sname[0] == "Normal":
                 # Blender wants GL normals, not DX (DirectX) ones:
                 # https://www.reddit.com/r/blender/comments/rbuaua/texture_contains_normaldx_and_normalgl_files/
-                continue
+                if 'dx' in tag_list:
+                    continue
+                if 'directx' in tag_list:
+                    continue
 
             matches = set(sname[1]).intersection(set(tag_list))
             if matches:

node_wrangler/util_test.py

@@ -225,6 +225,34 @@ class TestPutFileNamesInSockets(unittest.TestCase):
             },
         )
 
+    def test_texturecan(self):
+        """Texture from: https://www.texturecan.com/details/67/"""
+
+        files = [
+            MockFile("metal_0010_ao_1k.jpg"),
+            MockFile("metal_0010_color_1k.jpg"),
+            MockFile("metal_0010_height_1k.png"),
+            MockFile("metal_0010_metallic_1k.jpg"),
+            MockFile("metal_0010_normal_directx_1k.png"),
+            MockFile("metal_0010_normal_opengl_1k.png"),
+            MockFile("metal_0010_roughness_1k.jpg"),
+        ]
+        sockets = sockets_fixture()
+        match_files_to_socket_names(files, sockets)
+
+        assert_sockets(
+            self,
+            sockets,
+            {
+                "Ambient Occlusion": "metal_0010_ao_1k.jpg",
+                "Base Color": "metal_0010_color_1k.jpg",
+                "Displacement": "metal_0010_height_1k.png",
+                "Metallic": "metal_0010_metallic_1k.jpg",
+                "Normal": "metal_0010_normal_opengl_1k.png",
+                "Roughness": "metal_0010_roughness_1k.jpg",
+            },
+        )
+
 
 if __name__ == "__main__":
     unittest.main(verbosity=2)