v0.4.0 - TOML Writer Release πŸ”₯

mojo-toml now supports both reading and writing TOML files with full round-trip fidelity!

✨ New Features

TOML Writer: - to_toml() function - serialise Dict[String, TomlValue] to TOML string - Complete type support: strings, integers, floats, booleans, arrays, tables - String escaping, array formatting, table headers - Smart inline table heuristic (0-1 keys use inline format) - Full round-trip support: parse β†’ write β†’ parse preserves semantic equality

Example:

from toml import to_toml, TomlValue

var config = Dict[String, TomlValue]()
var app = Dict[String, TomlValue]()
app["name"] = TomlValue("MyApp")
app["version"] = TomlValue("1.0.0")
config["app"] = TomlValue(app^)

var toml_str = to_toml(config)
with open("config.toml", "w") as f:
    f.write(toml_str)

πŸ§ͺ Testing

  • 20 new basic type serialisation tests
  • 11 new table structure tests
  • 10 new round-trip fidelity tests
  • Critical: pixi.toml successfully round-trips
  • Total: 137 tests (96 parser + 41 writer)

πŸ“š Documentation

  • Updated README with read & write quickstart examples
  • Created docs/TOML_WRITER_DESIGN.md - implementation architecture
  • Updated WARP.md, TEST_ORGANIZATION.md, CHANGELOG.md
  • New examples/roundtrip.mojo demonstrating parse/modify/write workflow
  • Updated examples/quickstart.mojo with both reading and writing

πŸ”§ Technical Details

Writer Architecture: - 390-line src/toml/writer.mojo implementation - String escaping: \\, \", \n, \t, \r - Recursive nested table serialisation - Conservative inline table heuristic for readable output

Files Added: - src/toml/writer.mojo - tests/test_writer_basic.mojo - tests/test_writer_tables.mojo - tests/test_writer_roundtrip.mojo - examples/roundtrip.mojo - docs/TOML_WRITER_DESIGN.md - benchmarks/PLAN.md

πŸ“¦ Installation

Git submodule:

git submodule add https://github.com/databooth/mojo-toml vendor/mojo-toml
mojo -I vendor/mojo-toml/src your_app.mojo

Direct copy:

git clone https://github.com/databooth/mojo-toml
cp -r mojo-toml/src/toml your-project/lib/toml
mojo -I your-project/lib your_app.mojo

πŸ—ΊοΈ What’s Next

v0.5.0: TOML 1.0 completion - array of tables [[section]], hex/octal/binary integers
v0.6.0: Comparative Python benchmarks, memory profiling
Future: Separate mojo-ini package for INI file support

Full Changelog: https://github.com/DataBooth/mojo-toml/blob/main/CHANGELOG.md

Zero Python dependencies. Pure Mojo. MIT licensed.