Fix #142828: broken socket usage inference for some nodes

The issue was an oversight in f7f18cd0c7.

This patch also adds some unit tests that would have caught this error.

Pull Request: https://projects.blender.org/blender/blender/pulls/143026

tests/python/bl_node_socket_usage_inference.py

@@ -0,0 +1,84 @@
+# SPDX-FileCopyrightText: 2025 Blender Authors
+#
+# SPDX-License-Identifier: GPL-2.0-or-later
+
+import pathlib
+import sys
+import tempfile
+import bpy
+import unittest
+
+args = None
+
+
+class StructureTypeInferenceTest(unittest.TestCase):
+    @classmethod
+    def setUpClass(cls):
+        cls.testdir = args.testdir
+
+    def setUp(self):
+        self.assertTrue(self.testdir.exists(),
+                        "Test dir {0} should exist".format(self.testdir))
+
+    def load_testfile(self):
+        bpy.ops.wm.open_mainfile(filepath=str(self.testdir / "socket_usage_inference.blend"))
+
+    def assertUsed(self, socket):
+        self.assertTrue(socket.is_icon_visible)
+        self.assertFalse(socket.is_inactive)
+
+    def assertGrayedOut(self, socket):
+        self.assertTrue(socket.is_icon_visible)
+        self.assertTrue(socket.is_inactive)
+
+    def assertHidden(self, socket):
+        self.assertFalse(socket.is_icon_visible)
+
+    def test_geometry_nodes(self):
+        self.load_testfile()
+        tree = bpy.data.node_groups["Geometry Nodes"]
+
+        node = tree.nodes["Math Group"]
+        self.assertUsed(node.inputs["A"])
+        self.assertUsed(node.inputs["B"])
+
+        node = tree.nodes["Menu Switch Group"]
+        self.assertUsed(node.inputs["Menu"])
+        self.assertUsed(node.inputs["A"])
+        self.assertHidden(node.inputs["B"])
+
+        node = tree.nodes["Transform Matrix"]
+        self.assertUsed(node.inputs["Mode"])
+        self.assertUsed(node.inputs["Geometry"])
+        self.assertUsed(node.inputs["Transform"])
+        self.assertHidden(node.inputs["Translation"])
+        self.assertHidden(node.inputs["Rotation"])
+        self.assertHidden(node.inputs["Scale"])
+
+        node = tree.nodes["Transform Components"]
+        self.assertUsed(node.inputs["Mode"])
+        self.assertUsed(node.inputs["Geometry"])
+        self.assertUsed(node.inputs["Translation"])
+        self.assertUsed(node.inputs["Rotation"])
+        self.assertUsed(node.inputs["Scale"])
+        self.assertHidden(node.inputs["Transform"])
+
+
+def main():
+    global args
+    import argparse
+
+    if '--' in sys.argv:
+        argv = [sys.argv[0]] + sys.argv[sys.argv.index('--') + 1:]
+    else:
+        argv = sys.argv
+
+    parser = argparse.ArgumentParser()
+    parser.add_argument('--testdir', required=True, type=pathlib.Path)
+    args, remaining = parser.parse_known_args(argv)
+
+    unittest.main(argv=remaining)
+
+
+if __name__ == "__main__":
+    main()