Error calling / running Model via OMShell & OMPython - OpenModelica - modelica

Question

I am using the Dimensions model for placing parameters of the system that I use in many different models and call them by using extend, instead of declaring them again for each model. This is a simple example, but in reality, I have the way more of them.
A simple model with the structure I have:
package Main
model Dimensions
final parameter Modelica.SIunits.Length x = 10;
final parameter Modelica.SIunits.Length y = 5;
end Dimensions;
package Test_env
extends Main.Dimensions;
model Test_model
Real z;
equation
z = x + y;
end Test_model;
end Test_env;
end Main;
If I run this example in OMEdit it works without any problem. However, if I run it in OMShell or OMPython / OMCSessionZMQ it doesn't work.
Q - maybe I am using the extends clause incorrectly? If so, what would be the alternative of declaring parameters once and reusing them in other models?
This is what I get in OMShell:
>> loadFile("D:/1.Modelica/Simulations/Main.mo")
true
>> getClassNames()
{Main}
>> getClassNames(Main)
{Dimensions,Test_env}
>> getClassNames(Main.Test_env)
{Test_model}
>> simulate(Main.Test_env.Test_model, startTime=0, stopTime=1, numberOfIntervals=500, tolerance=1e-4, method="dassl", outputFormat="mat"); getErrorString()
record SimulationResult
resultFile = "",
simulationOptions = "startTime = 0.0, stopTime = 1.0, numberOfIntervals = 500, tolerance = 0.0001, method = 'dassl', fileNamePrefix = 'Main.Test_env.Test_model', options = '', outputFormat = 'mat', variableFilter = '.*', cflags = '', simflags = ''",
messages = "Failed to build model: Main.Test_env.Test_model",
timeFrontend = 0.0110966,
timeBackend = 0.0,
timeSimCode = 0.0,
timeTemplates = 0.0,
timeCompile = 0.0,
timeSimulation = 0.0,
timeTotal = 0.0111225
end SimulationResult;
"[D:/1.Modelica/Simulations/Main.mo:3:5-3:45:writable] Error: Class Modelica.SIunits.Length not found in scope Main.Dimensions.
[D:/1.Modelica/Simulations/Main.mo:1:1-18:9:writable] Error: Class Test_env.Test_model not found in scope Main.
Error: Class Main.Test_env.Test_model not found in scope .
Error: Error occurred while flattening model Main.Test_env.Test_model
"
And this is from OMPython / OMCSessionZMQ:
omc.sendExpression('simulate(Main.Test_env.Test_model, stopTime=1.0)')
---------------------------------------------------------------------------
{'resultFile': '',
'simulationOptions': "startTime = 0.0, stopTime = 1.0, numberOfIntervals = 500, tolerance = 1e-006, method = 'dassl', fileNamePrefix = 'Main.Test_env.Test_model', options = '', outputFormat = 'mat', variableFilter = '.*', cflags = '', simflags = ''",
'messages': 'Failed to build model: Main.Test_env.Test_model',
'timeFrontend': 0.0018766,
'timeBackend': 0.0,
'timeSimCode': 0.0,
'timeTemplates': 0.0,
'timeCompile': 0.0,
'timeSimulation': 0.0,
'timeTotal': 0.0018919}

Answer 1

To summarise the answers given via comments:
Use extends inside your model which will be extended.
package Test_env
model Test_model
Real z;
extends Main.Dimensions;
equation
z = x + y;
end Test_model;
end Test_env;
If all your models need the same fixed parameters it is still a good practise to add the extend to every model, so everybody knows where the variables come from.
Also compare with Modelica.Constants to see how the Modelica Standard Library defines constants. I used this to create the completed example:
package Main
model Dimensions
final constant Modelica.SIunits.Length x = 10;
final constant Modelica.SIunits.Length y = 5;
end Dimensions;
package Test_env
import Dim = Main.Dimensions;
model Test_model
Real z;
equation
z = Dim.x + Dim.y;
end Test_model;
end Test_env;
end Main;
And if you use something from a different package (here Modelica.SIunits.Length) you need to load the package. That's what your errors say with
Error: Class Modelica.SIunits.Length not found in scope Main.Dimensions.
In OpenModelica Modelica is already loaded on startup, so use loadModel(Modelica) or loadFile(...) in OMShell.
>> loadModel(Modelica)
true
>> loadFile("Path/To/Main.mo")
true
>> simulate(Main.Test_env.Test_model, startTime=0, stopTime=1, numberOfIntervals=500, tolerance=1e-4, method="dassl", outputFormat="mat")
record SimulationResult
resultFile = "C:/Users/USERNAME/AppData/Local/Temp/OpenModelica/Main.Test_env.Test_model_res.mat",
simulationOptions = "startTime = 0.0, stopTime = 1.0, numberOfIntervals = 500, tolerance = 0.0001, method = 'dassl', fileNamePrefix = 'Main.Test_env.Test_model', options = '', outputFormat = 'mat', variableFilter = '.*', cflags = '', simflags = ''",
messages = "LOG_SUCCESS | info | The initialization finished successfully without homotopy method.
LOG_SUCCESS | info | The simulation finished successfully.
",
timeFrontend = 0.3193980510936645,
timeBackend = 0.00467019998960375,
timeSimCode = 0.001078686094233897,
timeTemplates = 0.02625684206983937,
timeCompile = 9.15578961474681,
timeSimulation = 0.2440117147112652,
timeTotal = 9.751522705140404
end SimulationResult;
>>