throw error when variable not found

[Mathadon]

The line

ExternData/ExternData/Resources/C-Sources/ED_JSONFile.c

Line 136 in 2fb7395

ModelicaFormatMessage("Cannot find numeric value \"%s\" in file \"%s\"\n",

throws a message when a double cannot be found in a json file. It seems that the function then returns 0 as a default for that variable. When this message is overlooked by the user, it can result in completely wrong results that may go unnoticed. I would suggest to use ModelicaFormatError instead of ModelicaFormatMessage, or at least provide this as an optional flag. Note that for arrays an error is already thrown:

ExternData/ExternData/Resources/C-Sources/ED_JSONFile.c

Line 356 in 2fb7395

ModelicaFormatError("Cannot find array value \"%s\" in file \"%s\"\n",

[tbeu]

That was changed to ModelicaFormatMessage by purpose for #21 in the lack of any better ideas, see especially #21 (comment). There is a Boolean output argument signaling if a scalar variable is found or not.

[tbeu]

Reading my old commit message of bde9869 again I might change the message to ModelicaFormatWarning though.

[Mathadon]

In ExternData.Functions.JSON.getReal there could be an optional input generateError with default false? And based on that value you could decide whether to throw an error or a message (preferably warning, indeed).

[tbeu]

You can workaround this use case by checking the output argument exist of function ExternData.Functions.JSON.getReal and call Modelica.Utilities.Streams.error if it is set to false.

[Mathadon]

That indeed seems to be a valid workaround, but it is not that elegant (requires multiple lines of Modelica code). Is there something wrong with my suggestion?

[tbeu]

No, nothing wrong, except that I'd make it an enumertaion argument with values "No message", "Debug message", "Warning message" and "Error message". The other point is that it will require quite some time to do it in a consistent way for all functions provided by ExternData.

[Mathadon]

Let's see if I can help out.. If you can make a prototype implementation then I can replicate it for all JSON functions?

[tbeu]

It is not only JSON, but let me think about it.

[Mathadon]

I figured, but I rather not spend 10h on it either 😅 If the JSON ends up not being too much work then I might do all of them, but no promises there.

[Mathadon]

Any update on this? :)

[tbeu]

I am surprised that the proposed workaround did not work out for you. Nevertheless, the diagnostic behaviour for missing data is a configuration parameter now.

[Mathadon]

This works great, thanks a lot!