Yawn

A YAML parser for Scala

Overview

Yawn is a YAML parser for Scala, built on SnakeYAML, heavily influenced by jawn.

Yawn provides only a parser and plugin interface for constructing an AST. The AST is pluggable, and at present we provide modules for several popular Scala JSON AST implementations:

• argonaut
• circe

Dependencies

Yawn supports Scala 2.10 and 2.11, add the core dependency to your project:

SBT

val yawnVersion = "1.0.0"
libraryDependencies += "com.datasift.yawn" %% "yawn-core" % yawnVersion

Maven

<dependency>
    <groupId>com.datasift.yawn</groupId>
    <artifactId>yawn-core</artifactId>
    <version>1.0.0</version>
</dependency>

To use Yawn with your favourite JSON AST, also add a dependency to its support module:

Argonaut

libraryDependencies += "com.datasift.yawn" %% "yawn-argonaut" % yawnVersion

Circe

libraryDependencies += "com.datasift.yawn" %% "yawn-circe" % yawnVersion

Usage

To parse a YAML document, you'll first need to choose an AST; see above.

Argonaut

Parsing YAML with Argonaut works similarly to parsing JSON. Define your codec (or derive it automatically with argonaut-shapeless):

import argonaut._, Argonaut._

case class Person(name: String, age: Int, things: List[String])

implicit def PersonCodec = casecodec3(Person.apply, Person.unapply)("name", "age", "things")

Then use YamlParse to parse your YAML from a String:

import com.datasift.yawn.argonaut.YamlParse

val yaml = Source.fromFile("person.yaml").mkString
YamlParse.decodeOption[Person](yaml)

Note: Currently, yawn doesn't provide methods directly on String to decode YAML as Argonaut does for JSON. This is because these methods would conflict, and Argonaut wouldn't know whether to parse the String as JSON or YAML.

Instead, you must explicitly use YamlParse to work with YAML. Hopefully this issue will be solved in the future.

Circe

Parsing YAML with Circe works similarly to parsing JSON. Define your codec (or derive it automatically with circe-generic):

import io.circe._, io.circe.generic.auto._

case class Person(name: String, age: Int, things: List[String])

Then use yawn to parse your YAML from a String:

import com.datasift.yawn.circe.yawn._

val yaml = Source.fromFile("person.yaml").mkString
decode[Person](yaml)

License and Copyright

All code is available to you under the MIT license, available at http://opensource.org/licenses/mit-license.php.

Copyright DataSift Inc. 2016