From c88f6ed0e068bbae54ea84b166963ce44293a6fc Mon Sep 17 00:00:00 2001
From: Chen Zhang <zhangc@ornl.gov>
Date: Thu, 3 Oct 2024 18:16:40 -0400
Subject: [PATCH] Merge pull request #38144 from
 mantidproject/patch-add-direction-to-propwithval

Add optional direction to `PropertyWithValue` binding
---
 .../core/PropertyWithValueExporter.h          |  3 +-
 .../mantid/kernel/PropertyWithValueTest.py    | 33 +++++++++++++++++++
 .../Framework/Python/New_features/38144.rst   |  1 +
 3 files changed, 36 insertions(+), 1 deletion(-)
 create mode 100644 docs/source/release/v6.12.0/Framework/Python/New_features/38144.rst

diff --git a/Framework/PythonInterface/core/inc/MantidPythonInterface/core/PropertyWithValueExporter.h b/Framework/PythonInterface/core/inc/MantidPythonInterface/core/PropertyWithValueExporter.h
index 60594e269025..59f48596c61d 100644
--- a/Framework/PythonInterface/core/inc/MantidPythonInterface/core/PropertyWithValueExporter.h
+++ b/Framework/PythonInterface/core/inc/MantidPythonInterface/core/PropertyWithValueExporter.h
@@ -43,7 +43,8 @@ struct PropertyWithValueExporter {
     using namespace Mantid::Kernel;
 
     class_<PropertyWithValue<HeldType>, bases<Property>, boost::noncopyable>(
-        pythonClassName, init<std::string, HeldType>((arg("self"), arg("name"), arg("value"))))
+        pythonClassName, init<std::string, HeldType, unsigned int>(
+                             (arg("self"), arg("name"), arg("value"), arg("direction") = Direction::Input)))
         .add_property("value",
                       make_function(&PropertyWithValue<HeldType>::operator(), return_value_policy<ValueReturnPolicy>()))
         .def("dtype", &dtype<HeldType>, arg("self"));
diff --git a/Framework/PythonInterface/test/python/mantid/kernel/PropertyWithValueTest.py b/Framework/PythonInterface/test/python/mantid/kernel/PropertyWithValueTest.py
index 3badfe438b0e..04adc6a468dd 100644
--- a/Framework/PythonInterface/test/python/mantid/kernel/PropertyWithValueTest.py
+++ b/Framework/PythonInterface/test/python/mantid/kernel/PropertyWithValueTest.py
@@ -201,6 +201,39 @@ def test_set_property_of_vector_int_succeeds_with_numpy_array_of_int_type(self):
     def test_set_property_of_vector_int_succeeds_with_numpy_array_of_int_type(self):
         self._do_vector_int_numpy_test("WorkspaceIndexList")
 
+    def test_property_as_output(self):
+        """
+        Test that PropertyWithValue can be declared as an output property of an algorithm,
+        and that it will be returned as the output when called using the python API function approach
+        """
+        from mantid.api import AlgorithmFactory, PythonAlgorithm
+        from mantid.kernel import Direction, IntPropertyWithValue, ULongLongPropertyWithValue
+        from mantid.simpleapi import _create_algorithm_function
+        # a large number than cannot fit in a C++ int, requiring u_int64
+        BIGINT: int = 125824461545280
+        # create an algorithm that returns a ULongLongPropertyWithValue as the output
+        # then register it so that it can be called as a function
+        class MyAlgorithm(PythonAlgorithm):
+            def PyInit(self):
+                self.declareProperty(IntPropertyWithValue("InputInt", 0))
+                self.declareProperty(ULongLongPropertyWithValue("MyProperty", 0, direction=Direction.Output))
+            def PyExec(self):
+                self.setProperty("MyProperty", BIGINT)
+        AlgorithmFactory.subscribe(MyAlgorithm)
+        algo = MyAlgorithm()
+        algo.initialize()
+        myAlgorithmName = "MyAlgorithm"
+        _create_algorithm_function(myAlgorithmName, 1, algo)
+        from mantid.simpleapi import MyAlgorithm as MyAlgorithmInMantid
+        # call the algorithm, ensure the output is the large integer expected
+        ret = MyAlgorithmInMantid(1)
+        assert ret == BIGINT
+        # clean up the the algorithm manager and verify
+        AlgorithmFactory.unsubscribe(myAlgorithmName, 1)
+        with self.assertRaises(RuntimeError) as cm:
+            MyAlgorithmInMantid(2)
+        assert f"not registered {myAlgorithmName}" in str(cm.exception)
+
 
 if __name__ == "__main__":
     unittest.main()
diff --git a/docs/source/release/v6.12.0/Framework/Python/New_features/38144.rst b/docs/source/release/v6.12.0/Framework/Python/New_features/38144.rst
new file mode 100644
index 000000000000..5f8f0388d2b5
--- /dev/null
+++ b/docs/source/release/v6.12.0/Framework/Python/New_features/38144.rst
@@ -0,0 +1 @@
+- allows for declaring the many :class:`PropertyWithValue <mantid.kernel.FloatPropertyWithValue>` types as output properties from the python API.
\ No newline at end of file