Enabling rasterio.vrt.WarpedVRT with xr.open_rasterio

[scottyhq]

This is not a bug, but rather a feature request and discussion opener for changes to the open_rasterio function

Currently open_rasterio (xarray version 0.11) only accepts filepath strings and does not work with In-memory rasterio.vrt.WarpedVRT objects. I have a solution (see pull request), but it's likely not the best one (Many context managers can feel odd), see example below:

# Lazy in-memory warping from UTM to WGS84 lat/lon
with env:
    with rasterio.open(url) as src:
        da = xr.open_rasterio(src)
        print(da.crs, da.sizes)
        with WarpedVRT(src, crs='epsg:4326') as vrt:
            with xr.open_rasterio(vrt) as da:
                print(da.crs, da.sizes)

#+init=epsg:32610 (1, 7531, 7751)
#+init=epsg:4326 +no_defs (1, 5981, 9183)

More detailed gist here:
https://gist.github.com/scottyhq/ae90084adaf25e3b361b096d555c45f1

Problem description

In-memory “virtual” reprojection is a key feature of rasterio (see https://gist.github.com/sgillies/7e5cd548110a5b4d45ac1a1d93cb17a3), and it would be fantastic if this worked w/ xarray and dask distributed. Many workflows require warping between WGS84 lat/lon, UTM, Google Mercator, and rasterio can handle most any other projection.

related to: #1575, #2042, #2288
dask/dask#3255
Seems like some synergy here with geoxarray and salem
@mrocklin, @fmaussion, @geoxarray