Do not overwrite projections in the registry simply by using new ol.proj.Projection()

[ahocevar]

When proj4js is loaded, creating a projection with a SRS code that is already registered will cause the existing projection in the registry to be overwritten. This can become a problem e.g. when someone creates a projection object with a custom extent for use it in a specific context. That projection object with its custom extent would be set in the registry, causing it to be returned whenever ol.proj.get() is used with its SRS code.

[bartvde]

False alarm, I don't think I use such an override anymore, but it would be good to make a note in the release notes since this can potentially break people's apps?

[ahocevar]

In the snippet you linked, you use ol.proj.addProjection(). In this case whatever exists in the registry for that SRS code will still be overwritten.

My pull request only prevents that registry entries get overwritten by just creating a projection with new ol.proj.Projection(). If someone has been relying on this, then I would say they were relying on a buggy behavior, so no need to mention this in the release notes.

[bartvde]

Ah sorry then I misunderstood, I don't see a reason not to change the behaviour you point out.

[ahocevar]

@bartvde I updated the ticket title.

[bartvde]

LGTM @ahocevar

[elemoine]

Out of curiosity, can you still overwrite a projection in the registry if you want to?

[ahocevar]

Yes, using ol.proj.addProjection().

[elemoine]

Thanks.