nirfsg- Fix ErrorMessage API (#2174)

Author: rahur-NI

CHANGELOG.md

@@ -1708,6 +1708,7 @@
   - `numpy` is now an install dependency
   - gRPC support, enabling remote session management via NI gRPC Device Server
 - Changed
+  - Fixed `error_message` method to return the error string as output
 - Removed
 
 #### [nirfsg] 1.0.1 - 2026-01-09

docs/nirfsg/class.rst

@@ -1163,7 +1163,7 @@ error_message
 
     .. py:currentmodule:: nirfsg.Session
 
-    .. py:method:: error_message(error_code, error_message)
+    .. py:method:: error_message(error_code)
 
             Converts an error code returned by an NI-RFSG method into a user-readable string.
 
@@ -1184,17 +1184,16 @@ error_message
 
 
             :type error_code: int
-            :param error_message:
 
+            :rtype: str
+            :return:
 
-                Returns the user-readable message string that corresponds to the status code you specify.
 
-                You must pass a ViChar array with at least 256 bytes to this parameter.
+                    Returns the user-readable message string that corresponds to the status code you specify.
 
-                
+                    
 
 
-            :type error_message: str
 
 get_all_named_waveform_names
 ----------------------------

generated/nirfsg/nirfsg/_grpc_stub_interpreter.py

@@ -241,11 +241,12 @@ def disable_start_trigger(self):  # noqa: N802
             grpc_types.DisableStartTriggerRequest(vi=self._vi),
         )
 
-    def error_message(self, error_code, error_message):  # noqa: N802
-        self._invoke(
+    def error_message(self, error_code):  # noqa: N802
+        response = self._invoke(
             self._client.ErrorMessage,
-            grpc_types.ErrorMessageRequest(vi=self._vi, error_code=error_code, error_message=error_message),
+            grpc_types.ErrorMessageRequest(vi=self._vi, error_code=error_code),
         )
+        return response.error_message
 
     def get_all_named_waveform_names(self):  # noqa: N802
         response = self._invoke(

generated/nirfsg/nirfsg/_library_interpreter.py

@@ -298,13 +298,13 @@ def disable_start_trigger(self):  # noqa: N802
         errors.handle_error(self, error_code, ignore_warnings=False, is_error_handling=False)
         return
 
-    def error_message(self, error_code, error_message):  # noqa: N802
+    def error_message(self, error_code):  # noqa: N802
         vi_ctype = _visatype.ViSession(self._vi)  # case S110
         error_code_ctype = _visatype.ViStatus(error_code)  # case S150
-        error_message_ctype = ctypes.create_string_buffer(error_message.encode(self._encoding))  # case C020
+        error_message_ctype = (_visatype.ViChar * 256)()  # case C070
         error_code = self._library.niRFSG_ErrorMessage(vi_ctype, error_code_ctype, error_message_ctype)
         errors.handle_error(self, error_code, ignore_warnings=False, is_error_handling=True)
-        return
+        return error_message_ctype.value.decode(self._encoding)
 
     def get_all_named_waveform_names(self):  # noqa: N802
         vi_ctype = _visatype.ViSession(self._vi)  # case S110

generated/nirfsg/nirfsg/session.py

@@ -4833,7 +4833,7 @@ def disable_script_trigger(self):
         '''
         self._interpreter.disable_script_trigger(self._repeated_capability)
 
-    def error_message(self, error_code, error_message):
+    def error_message(self, error_code):
         r'''error_message
 
         Converts an error code returned by an NI-RFSG method into a user-readable string.
@@ -4845,12 +4845,13 @@ def error_message(self, error_code, error_message):
 
                 **Default Value** : 0 (VI_SUCCESS)
 
-            error_message (str): Returns the user-readable message string that corresponds to the status code you specify.
 
-                You must pass a ViChar array with at least 256 bytes to this parameter.
+        Returns:
+            error_message (str): Returns the user-readable message string that corresponds to the status code you specify.
 
         '''
-        self._interpreter.error_message(error_code, error_message)
+        error_message = self._interpreter.error_message(error_code)
+        return error_message
 
     @ivi_synchronized
     def _get_attribute_vi_boolean(self, attribute):

generated/nirfsg/nirfsg/unit_tests/_mock_helper.py

@@ -75,6 +75,7 @@ def __init__(self):
         self._defaults['DisableStartTrigger']['return'] = 0
         self._defaults['ErrorMessage'] = {}
         self._defaults['ErrorMessage']['return'] = 0
+        self._defaults['ErrorMessage']['errorMessage'] = None
         self._defaults['GetAllNamedWaveformNames'] = {}
         self._defaults['GetAllNamedWaveformNames']['return'] = 0
         self._defaults['GetAllNamedWaveformNames']['actualBufferSize'] = None
@@ -393,6 +394,15 @@ def niRFSG_DisableStartTrigger(self, vi):  # noqa: N802
     def niRFSG_ErrorMessage(self, vi, error_code, error_message):  # noqa: N802
         if self._defaults['ErrorMessage']['return'] != 0:
             return self._defaults['ErrorMessage']['return']
+        # error_message
+        if self._defaults['ErrorMessage']['errorMessage'] is None:
+            raise MockFunctionCallError("niRFSG_ErrorMessage", param='errorMessage')
+        test_value = self._defaults['ErrorMessage']['errorMessage']
+        if type(test_value) is str:
+            test_value = test_value.encode('ascii')
+        assert len(error_message) >= len(test_value)
+        for i in range(len(test_value)):
+            error_message[i] = test_value[i]
         return self._defaults['ErrorMessage']['return']
 
     def niRFSG_GetAllNamedWaveformNames(self, vi, waveform_names, buffer_size, actual_buffer_size):  # noqa: N802

src/nirfsg/metadata/functions.py

@@ -1423,9 +1423,9 @@
                 'use_in_python_api': True
             },
             {
-                'direction': 'in',
+                'direction': 'out',
                 'documentation': {
-                    'description': 'Returns the user-readable message string that corresponds to the status code you specify.\n\nYou must pass a ViChar array with at least 256 bytes to this parameter.'
+                    'description': 'Returns the user-readable message string that corresponds to the status code you specify.'
                 },
                 'name': 'errorMessage',
                 'size': {