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

[Martin Dobias]

Hi Andreas

On Wed, Jun 12, 2019 at 11:00 AM Andreas Neumann <a.neumann at carto.net> wrote:
>
> 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?

Rule key IDs are there to identify rules within a single layer. A rule
key being repeated in a different layer should do no harm. From what I
recall, the reason behind having rule keys is mainly to be able to
have unique identification for legend - e.g. if user enables or
disables a rule, we know which one it is based on the rule key
(otherwise we would need to use indexes of rules which are likely to
change when rules get added/removed/rearranged).

Hope that helps....

Cheers
Martin