Breaking Error if EditorMFunctionIndentType is originally blank

[Stephen M. Lee]

Summary

If 'EditorMFunctionIndentType' is unspecified for the first time using, then originalPreference = com.mathworks.services.Prefs.getStringPref('EditorMFunctionIndentType') will return an empty Java string. In this case, when the program tries to reset to original preferences, com.mathworks.services.Prefs.setStringPref('EditorMFunctionIndentType', originalPreference); will try to set an invalid setting in matlab.prf.

The fix is to check that length(originalPreference) > 0 before resetting to original preferences.

Environment

MATLAB 2019a

Minimum Example of Bug

>> originalPreference = java.lang.String(''); 
>> com.mathworks.services.Prefs.setStringPref('EditorMFunctionIndentType', originalPreference);
Java exception occurred:
java.lang.IllegalArgumentException: Unrecognized name:

	at com.mathworks.widgets.text.matlab.MatlabFunctionIndentingScheme.lookup(MatlabFunctionIndentingScheme.java:64)

	at com.mathworks.widgets.text.EditorPrefsAccessor.getMatlabIndentingScheme(EditorPrefsAccessor.java:257)

	at com.mathworks.widgets.STPPrefsManager$STPPrefsListener.prefChanged(STPPrefsManager.java:460)

	at com.mathworks.services.Prefs.notifyListeners(Prefs.java:1260)

	at com.mathworks.services.Prefs.setPrefValue(Prefs.java:1123)

	at com.mathworks.services.Prefs.setStringPref(Prefs.java:1021)

This will prevent MATLAB from opening properly in the future. To fix your settings you can either remove the preference or set to a valid option:

>> com.mathworks.services.Prefs.setStringPref('EditorMFunctionIndentType', 'MixedFunctionIndent');

Solution

The following code should prevent the above error

            ...

            originalPreference = com.mathworks.services.Prefs.getStringPref('EditorMFunctionIndentType');
            
            switch lower(indentationStrategy)
                case 'allfunctions'
                    com.mathworks.services.Prefs.setStringPref('EditorMFunctionIndentType', 'AllFunctionIndent');
                case 'nestedfunctions'
                    com.mathworks.services.Prefs.setStringPref('EditorMFunctionIndentType', 'MixedFunctionIndent');
                case 'noindent'
                    com.mathworks.services.Prefs.setStringPref('EditorMFunctionIndentType', 'ClassicFunctionIndent');
            end
            
            editorPage.smartIndentContents();

            % Restore original settings, if necessary
            if (length(originalPreference) > 0 && originalPreference ~= com.mathworks.services.Prefs.getStringPref('EditorMFunctionIndentType'))
                com.mathworks.services.Prefs.setStringPref('EditorMFunctionIndentType', originalPreference);
            end

            ...