[QGIS-Developer] How important are rule ids (keys) in QGIS project files?

[Andreas Neumann]

Hi again, 

During our tests and investigations around rendering problems in QGIS we
found the following issue, which is really easy to reproduce: 

1. Create a layer (any vector source) 

2. Create a rule based symbology (e.g. by going through a
classification) 

3. Save qgs file 

4. Export style file of first layer 

5. Load the same layer as above in the project, so that the same layer
is loaded twice 

6. import the style from from point 4 and assign it to the second layer 

7. save qgis project file 

8. open the project file in text editor --> all rule keys now exist
twice. 

Now my question: will we run into problems because of these duplicated
rule keys? If this is a problem - why is QGIS not taking care about
making the rule ids unique by generating new uuid keys on importing the
qml style file? Is this a bug in QGIS? Or are all of these rule keys
totally irrelevant? If they are irrelevant, why do they exist in the
project? 

Thanks for the discussion, 

Andreas
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