Alan D. Snow

I should have explained what I was thinking better. I was thinking that the code could build the regex from the list of domain postfixes. For example: RIO_AWS_S3_DOMAINS=s3.acme.org,s3.foo.com Internal regex...

Probably a good idea to document this. How about here https://github.com/rasterio/rasterio/blob/main/docs/topics/vsi.rst?

@emmanuelmathot, thoughts about updating this PR to support `AWS_S3_ENDPOINT` instead?

@sgillies, your logic makes sense to me - thanks for working on this :+1:

@sgillies, thoughts about adding more tests? Could start by copying some from #2698. I am thinking it would be good to verify that the bounds/transform/data of the merged VRT are...

> A virtual dataset could be a thin wrapper around an XML bytestring. I like that idea.

@sgillies, I am thinking that it may make sense to move the `VirtualDataset` to a separate PR. I think that will help focus the discussion. Thoughts?

I had a thought that analogous to [pyproj CRS building](https://pyproj4.github.io/pyproj/stable/build_crs.html) there could potentially be sub-elements for a VRTDataset represented as classes that could be used to build a VRTDataset.

Schema reference: https://raw.githubusercontent.com/OSGeo/gdal/master/data/gdalvrt.xsd

I am thinking this is an OSX arm64 specific issue. I had no issues on Linux installing from pip. ```python from rasterio.crs import CRS from affine import Affine import rasterio...