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Fix the python session to return correct error message when invalid session for MI drivers #2181

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Fix the python session to return correct error message when invalid session for MI drivers #2181

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82373f8
Added self.set_session_handle()
zoechanzy Jun 29, 2026
ab14a93
Add unit test
zoechanzy Jun 29, 2026
5788750
Use comment instead of docstring
zoechanzy Jul 2, 2026
4b16c37
Update get_error_description
zoechanzy Jul 2, 2026
d239d81
Save session before next try block
zoechanzy Jul 2, 2026
dfb69f2
Update comments
zoechanzy Jul 2, 2026
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25 changes: 20 additions & 5 deletions build/templates/_library_interpreter.py/_get_error_description.py.mako
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Original file line number Diff line number Diff line change
Expand Up @@ -21,14 +21,29 @@
% if 'error_message' in config['functions']:

try:
'''
It is expected for get_error to raise when the session is invalid
(IVI spec requires GetError to fail).
Use error_message instead. It doesn't require a session.
'''
# get_error reads the session's error queue, which may have been overwritten,
# causing it to return a mismatched error code. error_message takes the error
# code directly as a parameter and looks up its description without reading the
# queue, it will return the description for the specific error code.
# Use error_message in current session before the handle reset in the next block.

error_string = self.error_message(error_code)
return error_string
except errors.Error:
pass

save_vi = self.get_session_handle()
try:
# It is expected for get_error to raise when the session is invalid
# (IVI spec requires GetError to fail).
# Use error_message instead. It doesn't require a session.

self.set_session_handle()
error_string = self.error_message(error_code)
return error_string
except errors.Error:
pass
finally:
self.set_session_handle(save_vi)
% endif
return "Failed to retrieve error description."
25 changes: 20 additions & 5 deletions generated/nidcpower/nidcpower/_library_interpreter.py
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Original file line number Diff line number Diff line change
Expand Up @@ -104,15 +104,30 @@ def get_error_description(self, error_code):
pass

try:
'''
It is expected for get_error to raise when the session is invalid
(IVI spec requires GetError to fail).
Use error_message instead. It doesn't require a session.
'''
# get_error reads the session's error queue, which may have been overwritten,
# causing it to return a mismatched error code. error_message takes the error
# code directly as a parameter and looks up its description without reading the
# queue, it will return the description for the specific error code.
# Use error_message in current session before the handle reset in the next block.

error_string = self.error_message(error_code)
return error_string
except errors.Error:
pass
Comment on lines +113 to +116

@ni-jfitzger ni-jfitzger Jun 29, 2026

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It is possible that the session is valid but the returned_error_code unequal to error_code

If this happens, then something likely went wrong retrieving the error message. I'm not sure calling error_message instead of get_error_description is going to change anything in that case.

@zoechanzy zoechanzy Jun 30, 2026

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Calling get_error_description again might cause infinite loop.

@ni-jfitzger ni-jfitzger Jun 30, 2026 •
edited
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No, I wasn't suggesting that we call get_error_description again. I'm merely trying to think about what behavior we'll see if this new section of code executes.

Oh, i see. Sorry, I meant get_error, not get_error_description.

@jfan-1995 jfan-1995 Jul 2, 2026 •
edited
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I also find this comment a bit confusing....

What I understand is get_error reads what is currently in the session, if it is overwritten or cleared it could still successfully run but will return mismatched error code.

So this try block is to check the error_message in the current session first before proceed to the set_session_handle in the next try block.

@jfan-1995 jfan-1995 Jul 2, 2026 •
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How about wording the comment to be like this?

# get_error reads the session's error queue, which may have been overwritten,
# causing it to return a mismatched error code. error_message takes the error
# code directly as a parameter and looks up its description without reading the
# queue, so it will just return the description for the specific error code.
# Try it here with the current session before the handle reset in the next block.


save_vi = self.get_session_handle()
try:
# It is expected for get_error to raise when the session is invalid
# (IVI spec requires GetError to fail).
# Use error_message instead. It doesn't require a session.

self.set_session_handle()
error_string = self.error_message(error_code)
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return error_string
except errors.Error:
pass
finally:
self.set_session_handle(save_vi)
return "Failed to retrieve error description."

def abort(self, channel_name): # noqa: N802
Expand Down
25 changes: 20 additions & 5 deletions generated/nidigital/nidigital/_library_interpreter.py
View file
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Original file line number Diff line number Diff line change
Expand Up @@ -102,15 +102,30 @@ def get_error_description(self, error_code):
pass

try:
'''
It is expected for get_error to raise when the session is invalid
(IVI spec requires GetError to fail).
Use error_message instead. It doesn't require a session.
'''
# get_error reads the session's error queue, which may have been overwritten,
# causing it to return a mismatched error code. error_message takes the error
# code directly as a parameter and looks up its description without reading the
# queue, it will return the description for the specific error code.
# Use error_message in current session before the handle reset in the next block.

error_string = self.error_message(error_code)
return error_string
except errors.Error:
pass

save_vi = self.get_session_handle()
try:
# It is expected for get_error to raise when the session is invalid
# (IVI spec requires GetError to fail).
# Use error_message instead. It doesn't require a session.

self.set_session_handle()
error_string = self.error_message(error_code)
return error_string
except errors.Error:
pass
finally:
self.set_session_handle(save_vi)
return "Failed to retrieve error description."

def abort(self): # noqa: N802
Expand Down
25 changes: 20 additions & 5 deletions generated/nidmm/nidmm/_library_interpreter.py
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Original file line number Diff line number Diff line change
Expand Up @@ -100,15 +100,30 @@ def get_error_description(self, error_code):
pass

try:
'''
It is expected for get_error to raise when the session is invalid
(IVI spec requires GetError to fail).
Use error_message instead. It doesn't require a session.
'''
# get_error reads the session's error queue, which may have been overwritten,
# causing it to return a mismatched error code. error_message takes the error
# code directly as a parameter and looks up its description without reading the
# queue, it will return the description for the specific error code.
# Use error_message in current session before the handle reset in the next block.

error_string = self.error_message(error_code)
return error_string
except errors.Error:
pass

save_vi = self.get_session_handle()
try:
# It is expected for get_error to raise when the session is invalid
# (IVI spec requires GetError to fail).
# Use error_message instead. It doesn't require a session.

self.set_session_handle()
error_string = self.error_message(error_code)
return error_string
except errors.Error:
pass
finally:
self.set_session_handle(save_vi)
return "Failed to retrieve error description."

def abort(self): # noqa: N802
Expand Down
25 changes: 20 additions & 5 deletions generated/nifake/nifake/_library_interpreter.py
View file
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Original file line number Diff line number Diff line change
Expand Up @@ -116,15 +116,30 @@ def get_error_description(self, error_code):
pass

try:
'''
It is expected for get_error to raise when the session is invalid
(IVI spec requires GetError to fail).
Use error_message instead. It doesn't require a session.
'''
# get_error reads the session's error queue, which may have been overwritten,
# causing it to return a mismatched error code. error_message takes the error
# code directly as a parameter and looks up its description without reading the
# queue, it will return the description for the specific error code.
# Use error_message in current session before the handle reset in the next block.

error_string = self.error_message(error_code)
return error_string
except errors.Error:
pass

save_vi = self.get_session_handle()
try:
# It is expected for get_error to raise when the session is invalid
# (IVI spec requires GetError to fail).
# Use error_message instead. It doesn't require a session.

self.set_session_handle()
error_string = self.error_message(error_code)
return error_string
except errors.Error:
pass
finally:
self.set_session_handle(save_vi)
return "Failed to retrieve error description."

def abort(self): # noqa: N802
Expand Down
30 changes: 30 additions & 0 deletions generated/nifake/nifake/unit_tests/test_library_interpreter.py
View file
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Original file line number Diff line number Diff line change
Expand Up @@ -716,6 +716,36 @@ def test_get_error_description_error_message_error(self):
assert e.description == test_error_desc
self.patched_library.niFake_error_message.assert_called_once_with(_matchers.ViSessionMatcher(SESSION_NUM_FOR_TEST), _matchers.ViInt32Matcher(test_error_code), _matchers.ViCharBufferMatcher(256))

def test_get_error_description_error_message_after_session_reset(self):
test_error_code = -42
test_error_desc = "The answer to the ultimate question"
self.patched_library.niFake_PoorlyNamedSimpleFunction.side_effect = self.side_effects_helper.niFake_PoorlyNamedSimpleFunction
self.side_effects_helper['PoorlyNamedSimpleFunction']['return'] = test_error_code
self.patched_library.niFake_GetError.side_effect = self.side_effects_helper.niFake_GetError
self.side_effects_helper['GetError']['errorCode'] = -1
self.side_effects_helper['GetError']['description'] = "Shouldn't get this"
self.side_effects_helper['GetError']['return'] = -2
self.side_effects_helper['error_message']['errorMessage'] = test_error_desc

def error_message_side_effect(vi, error_code, error_message_buf):
if vi.value == SESSION_NUM_FOR_TEST:
return -3
return self.side_effects_helper.niFake_error_message(vi, error_code, error_message_buf)

self.patched_library.niFake_error_message.side_effect = error_message_side_effect
interpreter = self.get_initialized_library_interpreter()
try:
interpreter.simple_function()
assert False
except nifake.Error as e:
assert e.code == test_error_code
assert e.description == test_error_desc
assert self.patched_library.niFake_error_message.call_count == 2
self.patched_library.niFake_error_message.assert_has_calls([
call(_matchers.ViSessionMatcher(SESSION_NUM_FOR_TEST), _matchers.ViInt32Matcher(test_error_code), _matchers.ViCharBufferMatcher(256)),
call(_matchers.ViSessionMatcher(0), _matchers.ViInt32Matcher(test_error_code), _matchers.ViCharBufferMatcher(256)),
])

# Custom types

def test_set_custom_type(self):
Expand Down
25 changes: 20 additions & 5 deletions generated/nifgen/nifgen/_library_interpreter.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -100,15 +100,30 @@ def get_error_description(self, error_code):
pass

try:
'''
It is expected for get_error to raise when the session is invalid
(IVI spec requires GetError to fail).
Use error_message instead. It doesn't require a session.
'''
# get_error reads the session's error queue, which may have been overwritten,
# causing it to return a mismatched error code. error_message takes the error
# code directly as a parameter and looks up its description without reading the
# queue, it will return the description for the specific error code.
# Use error_message in current session before the handle reset in the next block.

error_string = self.error_message(error_code)
return error_string
except errors.Error:
pass

save_vi = self.get_session_handle()
try:
# It is expected for get_error to raise when the session is invalid
# (IVI spec requires GetError to fail).
# Use error_message instead. It doesn't require a session.

self.set_session_handle()
error_string = self.error_message(error_code)
return error_string
except errors.Error:
pass
finally:
self.set_session_handle(save_vi)
return "Failed to retrieve error description."

def abort(self): # noqa: N802
Expand Down
25 changes: 20 additions & 5 deletions generated/niscope/niscope/_library_interpreter.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -104,15 +104,30 @@ def get_error_description(self, error_code):
pass

try:
'''
It is expected for get_error to raise when the session is invalid
(IVI spec requires GetError to fail).
Use error_message instead. It doesn't require a session.
'''
# get_error reads the session's error queue, which may have been overwritten,
# causing it to return a mismatched error code. error_message takes the error
# code directly as a parameter and looks up its description without reading the
# queue, it will return the description for the specific error code.
# Use error_message in current session before the handle reset in the next block.

error_string = self.error_message(error_code)
return error_string
except errors.Error:
pass

save_vi = self.get_session_handle()
try:
# It is expected for get_error to raise when the session is invalid
# (IVI spec requires GetError to fail).
# Use error_message instead. It doesn't require a session.

self.set_session_handle()
error_string = self.error_message(error_code)
return error_string
except errors.Error:
pass
finally:
self.set_session_handle(save_vi)
return "Failed to retrieve error description."

def abort(self): # noqa: N802
Expand Down
25 changes: 20 additions & 5 deletions generated/niswitch/niswitch/_library_interpreter.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -100,15 +100,30 @@ def get_error_description(self, error_code):
pass

try:
'''
It is expected for get_error to raise when the session is invalid
(IVI spec requires GetError to fail).
Use error_message instead. It doesn't require a session.
'''
# get_error reads the session's error queue, which may have been overwritten,
# causing it to return a mismatched error code. error_message takes the error
# code directly as a parameter and looks up its description without reading the
# queue, it will return the description for the specific error code.
# Use error_message in current session before the handle reset in the next block.

error_string = self.error_message(error_code)
return error_string
except errors.Error:
pass

save_vi = self.get_session_handle()
try:
# It is expected for get_error to raise when the session is invalid
# (IVI spec requires GetError to fail).
# Use error_message instead. It doesn't require a session.

self.set_session_handle()
error_string = self.error_message(error_code)
return error_string
except errors.Error:
pass
finally:
self.set_session_handle(save_vi)
return "Failed to retrieve error description."

def abort(self): # noqa: N802
Expand Down
30 changes: 30 additions & 0 deletions src/nifake/unit_tests/test_library_interpreter.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -716,6 +716,36 @@ def test_get_error_description_error_message_error(self):
assert e.description == test_error_desc
self.patched_library.niFake_error_message.assert_called_once_with(_matchers.ViSessionMatcher(SESSION_NUM_FOR_TEST), _matchers.ViInt32Matcher(test_error_code), _matchers.ViCharBufferMatcher(256))

def test_get_error_description_error_message_after_session_reset(self):
test_error_code = -42
test_error_desc = "The answer to the ultimate question"
self.patched_library.niFake_PoorlyNamedSimpleFunction.side_effect = self.side_effects_helper.niFake_PoorlyNamedSimpleFunction
self.side_effects_helper['PoorlyNamedSimpleFunction']['return'] = test_error_code
self.patched_library.niFake_GetError.side_effect = self.side_effects_helper.niFake_GetError
self.side_effects_helper['GetError']['errorCode'] = -1
self.side_effects_helper['GetError']['description'] = "Shouldn't get this"
self.side_effects_helper['GetError']['return'] = -2
self.side_effects_helper['error_message']['errorMessage'] = test_error_desc

def error_message_side_effect(vi, error_code, error_message_buf):
if vi.value == SESSION_NUM_FOR_TEST:
return -3
return self.side_effects_helper.niFake_error_message(vi, error_code, error_message_buf)

self.patched_library.niFake_error_message.side_effect = error_message_side_effect
interpreter = self.get_initialized_library_interpreter()
try:
interpreter.simple_function()
assert False
except nifake.Error as e:
assert e.code == test_error_code
assert e.description == test_error_desc
assert self.patched_library.niFake_error_message.call_count == 2
self.patched_library.niFake_error_message.assert_has_calls([
call(_matchers.ViSessionMatcher(SESSION_NUM_FOR_TEST), _matchers.ViInt32Matcher(test_error_code), _matchers.ViCharBufferMatcher(256)),
call(_matchers.ViSessionMatcher(0), _matchers.ViInt32Matcher(test_error_code), _matchers.ViCharBufferMatcher(256)),
])

# Custom types

def test_set_custom_type(self):
Expand Down
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