sparsetech / toml-scala

TOML parser with codec derivation for the Scala platform

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toml-scala

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toml-scala is a feature-complete implementation of TOML for the Scala platform. It can parse TOML content into an AST or map it onto case class hierarchies. Furthermore, it can generate TOML back from an AST.

Features

  • Standard-compliant
  • AST parsing
  • Codec derivation
    • Optional values
    • Custom codecs
  • Generating TOML from ASTs
  • Error handling
  • Property-based unit tests

Compatibility

Back end Scala versions Date support Tests
JVM 2.11, 2.12, 2.13 Yes Yes
JavaScript 2.11, 2.12, 2.13 No (1) Yes
LLVM 2.11 No (1) Partially (2)
  • (1) JavaScript and LLVM have insufficient support for the JDK8's java.time. Parsing of dates and times is presently only possible under the JVM.
  • (2) Presently, Scala Native does not support running ScalaCheck test suites.

Dependencies

libraryDependencies += "tech.sparse" %%  "toml-scala" % "<version>"  // JVM
libraryDependencies += "tech.sparse" %%% "toml-scala" % "<version>"  // JavaScript, LLVM

Examples

AST parsing

toml.Toml.parse("a = 1")  // Right(Tbl(Map(a -> Num(1))))

Codec derivation

The following import is needed:

import toml.Codecs._

Tables

case class Table(b: Int)
case class Root(a: Int, table: Table)

val table =
  """
    |a = 1
    |[table]
    |b = 2
  """.stripMargin

Toml.parseAs[Root](table)  // Right(Root(1, Table(2)))

Table lists

val tableList =
  """
    |points = [ { x = 1, y = 2, z = 3 },
    |           { x = 7, y = 8, z = 9 },
    |           { x = 2, y = 4, z = 8 } ]
  """.stripMargin

case class Point(x: Int, y: Int, z: Int)
case class Root(points: List[Point])

Toml.parseAs[Root](tableList)
// Right(Root(List(
//   Point(1, 2, 3),
//   Point(7, 8, 9),
//   Point(2, 4, 8))))

Lists can be mapped onto case classes as a shorter alternative. Therefore, the following notation would yield the same result:

points = [ [ 1, 2, 3 ],
           [ 7, 8, 9 ],
           [ 2, 4, 8 ] ]

Optional values

case class Table(b: Int)
case class Root(a: Int, table: Option[Table])

Toml.parseAs[Root]("a = 1")  // Right(Root(1, None))

Define custom codecs

case class Currency(name: String)
implicit val currencyCodec: Codec[Currency] = Codec {
  case (Value.Str(value), _, _) =>
    value match {
      case "EUR" => Right(Currency("EUR"))
      case "BTC" => Right(Currency("BTC"))
      case _     => Left((List(), s"Invalid currency: $value"))
    }

  case (value, _, _) => Left((List(), s"Currency expected, $value provided"))
}

case class Root(currency: Currency)
Toml.parseAs[Root]("""currency = "BTC"""")  // Right(Root(Currency(BTC)))

Generate TOML

val root = Root(List(Pair("scalaDeps", Arr(List(
  Arr(List(Str("io.monix"), Str("minitest"), Str("2.2.2"))),
  Arr(List(Str("org.scalacheck"), Str("scalacheck"), Str("1.14.0"))),
  Arr(List(Str("org.scalatest"), Str("scalatest"), Str("3.2.0-SNAP10")))
)))))

Toml.generate(root)

Returns:

scalaDeps = [
  ["io.monix", "minitest", "2.2.2"],
  ["org.scalacheck", "scalacheck", "1.14.0"],
  ["org.scalatest", "scalatest", "3.2.0-SNAP10"]
]

Language Extensions

toml-scala supports the following language extensions which are disabled by default:

To enable them, pass in a set of extensions to the parse() or parseAs() function as a second argument:

toml.Toml.parse("""key = {
  a = 23,
  b = 42,
}""", Set(toml.Extension.MultiLineInlineTables))

Links

Licence

toml-scala is licensed under the terms of the Mozilla Public Licence v2.0.

Credits

The rules and their respective tests were derived from stoml by Jorge Vicente Cantero.

toml-scala is based on top of FastParse for defining the language rules. ScalaCheck allows us to test synthetic examples of TOML files. The codec derivation was implemented using Shapeless.

Contributors

  • Tim Nieradzik