Read, Write, and Modify TOML files in R

Simple toolkit for parsing and generating TOML text. Based on toml_edit which allows for modifying toml while preserving order, comments, and whitespace.

We currently use a WebAssembly build of toml_edit such that we do not have to deal with Rust code in R and everything works without compilation on any platform, including WebR. When Rust becomes better supported on CRAN and WebR, we could consider binding to Rust directly, although it does not make too much of a difference.

Installation requires no compilation:

install.packages("toml")

The edit_toml function simply takes a TOML string and returns the modified TOML string:

# Read some TOML dadta
toml <- readLines('https://raw.githubusercontent.com/posit-dev/air/refs/heads/main/Cargo.toml')

# Modify some fields
toml <- edit_toml(toml, 'workspace.package.rust-version', '1.84')
toml <- edit_toml(toml, 'workspace.dependencies.bla', list(path = "./yolo", rev = "123"))
print(toml)

You can also parse the toml into an R list:

parse_toml(toml)