Potentially breaking change: Default decoded GeoJSON to SRID 4326 (WGS 84)

This aligns our GeoJSON decoding with the GeoJSON spec by making all decoded GeoJSON infer the WGS 84 datum (SRID 4326) by default. Whereas previously when you called Geo.JSON.decode/1 or decode!/1, we would return geometries with an :srid of nil, we now return srid: 4326. Likewise when encoding GeoJSON, we explicitly output a crs field indicating the datum.

This is unlikely to break real-world usage unless your implementation was assuming a different datum by default.

A couple examples of the changes:

Before:

iex> Geo.JSON.decode!(%{"type" => "Point", "coordinates" => [1.0, 2.0]})
%Geo.Point{
  coordinates: {1.0, 2.0},
  # Note the old default nil SRID!
  srid: nil
}

After

iex> Geo.JSON.decode!(%{"type" => "Point", "coordinates" => [1.0, 2.0]})
%Geo.Point{
  coordinates: {1.0, 2.0},
  # New explicit default of WGS 84
  srid: 4326
}

If you were to then encode this value again, you'd end up with a new crs field in the output GeoJSON:

iex> %{"type" => "Point", "coordinates" => [1.0, 2.0]}
...> |> Geo.JSON.decode!()
...> |> GeoJSON.encode!()
%{
  "type" => "Point",
  "coordinates" => [1.0, 2.0],
  # Note the new `crs` field which was not present in the input to Geo.JSON.decode!/1
  "crs" => %{"properties" => %{"name" => "EPSG:4326"}, "type" => "name"}
}

This last behavior is the most potentially troublesome. However, we don't have a good way of distinguishing a case where you explicitly had the crs set in the input to the decoding function (in which case you would probably also like to have it present in the re-encoded version) compared to one in which it's been inferred.

Thanks to @gworkman for reporting this issue (#129).

Potentially breaking change: Convert string coordinates to floats, or raise an error

This fixes an issue where we were silently accepting non-numeric coordinates in the GeoJSON decoder, such that you could wind up doing things like decoding a point like %Geo.Point{coordinates: {"100.0", "-10.0"}}. This would obviously not have gone well for you later in your processing pipeline, and it violates our typespecs.

The fix here, suggested by @LostKobrakai, is to convert those strings to numbers where we can do so unambiguously. While such inputs are clearly invalid, it's easy enough to handle them in the way that the user was hoping that we should probably just do it. In cases where there's any ambiguity at all, we raise an ArgumentError.

Other bug fixes in v4.0.0

• Support GeoJSON Feature object with nested GeometryCollection by new contributor @carstenpiepel (🎉)

Other changes in v4.0.0

• Fix typo in the README by @caspg
• Fix typo by new contributor @preciz (🎉)
• Optional dependency bump for jason to v1.4.4
• Dev dependency bumps for ex_doc, benchee, stream_data

Full Changelog: https://github.com/felt/geo/compare/v3.6.0...v4.0.0