feather 0.4.0

This release updates feather to depend on the arrow package, which is where Feather format development has moved. This resolves many bug reports and missing features from the previous implementation of Feather in R, and it brings the R package in line with the Python feather package, which has depended on pyarrow since 2017.

For compatibility, feather::write_feather() uses V1 of the Feather specification: it is a wrapper around arrow::write_feather(version = 1). Feather V2 is just the Arrow format on disk and has support for a much richer set of data types. To switch to V2, we recommend just using arrow::write_feather().

With these changes, most of feather's APIs are preserved in spirit, but there are some noteworthy changes:

• The feather class, which allowed for accessing data in a Feather file without reading it all into R, has been replaced by an arrow::Table backed by the memory-mapped Feather file. This should preserve the intent of the original implementation but with much richer functionality. One behavior change that results though is that slicing/extracting from the Table results in another arrow Table, so the data aren't pulled into a data.frame until you as.data.frame() them.

• feather_metadata also now does the same.