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jawn

A fast JSON parser for Scala.

Merino is a JSON parser, and nothing more. It provides just a single parse method that reads a stream of bytes and returns structured data.

• bare-bones JSON parsing
• provides a single parse method
• produces "raw" output, mostly as primitive types
• optimized for performance

Merino jawn has not yet been published. The medium-term plan is to build Merino jawn with Fury and to publish it as a source build on Vent. This will enable ordinary users to write and build software which depends on Merino jawn.

Subsequently, Merino jawn will also be made available as a binary in the Maven Central repository. This will enable users of other build tools to use it.

For the overeager, curious and impatient, see building.

Merino will parse a DataStream, that is, a LazyList[IArray[Byte]]. This makes it easy to parse any type which can be converted to a byte array or a lazy stream.

The JsonAst.parse method will parse the input and return a JsonAst, which is an opaque type alias for the union of the following types:

• Long, Double and BigDecimal, representing JSON number types,
• String for JSON strings,
• Boolean for JSON true and false values,
• Null for the null value,
• IArray[Any] representing a JSON array, and,
• (IArray[String], IArray[Any]) representing a JSON object

Note that which type of Long, Double or BigDecimal the parser chooses to represent a given number will be determined by whether the type can represent the number, as specified in the JSON source, precisely.

The types IArray[Any] and (IArray[String], IArray[Any]), representing arrays and objects, will only ever contain JsonAst-typed values, despite having type parameters of Any. But type aliases cannot refer to themselves, so Any is used instead.

Additionally, the type (IArray[String], IArray[Any]) was chosen as an alternative to IArray[(String, Any)] since the former requires 2n + 3 objects to be constructed for each field in the JSON object, as opposed to 3n + 1 in the latter case: for anything but an object of exactly one key, the former requires fewer objects to be created. Additionally, the types may be disambiguated reflectively by their erased types.

If parsing fails, a JsonParseError will be thrown, including the line and column in which the error occurs, and an enumeration value (of type JsonParseError.Issue) describing the error.

Merino jawn is classified as maturescent. For reference, Soundness projects are categorized into one of the following five stability levels:

• embryonic: for experimental or demonstrative purposes only, without any guarantees of longevity
• fledgling: of proven utility, seeking contributions, but liable to significant redesigns
• maturescent: major design decisions broady settled, seeking probatory adoption and refinement
• dependable: production-ready, subject to controlled ongoing maintenance and enhancement; tagged as version 1.0.0 or later
• adamantine: proven, reliable and production-ready, with no further breaking changes ever anticipated

Projects at any stability level, even embryonic projects, can still be used, as long as caution is taken to avoid a mismatch between the project's stability level and the required stability and maintainability of your own project.

Merino jawn is designed to be small. Its entire source code currently consists of 785 lines of code.

Merino jawn will ultimately be built by Fury, when it is published. In the meantime, two possibilities are offered, however they are acknowledged to be fragile, inadequately tested, and unsuitable for anything more than experimentation. They are provided only for the necessity of providing some answer to the question, "how can I try Merino jawn?".

1. Copy the sources into your own project

   Read the fury file in the repository root to understand Merino jawn's build structure, dependencies and source location; the file format should be short and quite intuitive. Copy the sources into a source directory in your own project, then repeat (recursively) for each of the dependencies.

   The sources are compiled against the latest nightly release of Scala 3. There should be no problem to compile the project together with all of its dependencies in a single compilation.

2. Build with Wrath

   Wrath is a bootstrapping script for building Merino jawn and other projects in the absence of a fully-featured build tool. It is designed to read the fury file in the project directory, and produce a collection of JAR files which can be added to a classpath, by compiling the project and all of its dependencies, including the Scala compiler itself.

   Download the latest version of wrath, make it executable, and add it to your path, for example by copying it to /usr/local/bin/.

   Clone this repository inside an empty directory, so that the build can safely make clones of repositories it depends on as peers of merino jawn. Run wrath -F in the repository root. This will download and compile the latest version of Scala, as well as all of Merino jawn's dependencies.

   If the build was successful, the compiled JAR files can be found in the .wrath/dist directory.

Contributors to Merino jawn are welcome and encouraged. New contributors may like to look for issues marked [beginner](https://github.com/propensive/merino jawn/labels/beginner).

We suggest that all contributors read the Contributing Guide to make the process of contributing to Merino jawn easier.

Please do not contact project maintainers privately with questions unless there is a good reason to keep them private. While it can be tempting to repsond to such questions, private answers cannot be shared with a wider audience, and it can result in duplication of effort.

Merino jawn was designed and developed by Jon Pretty, and commercial support and training on all aspects of Scala 3 is available from Propensive OÜ.

Merino is named after the variety of sheep known for the quality of their fleeces, in keeping with the trend for JSON libraries to allude to the story of Jason and the Argonauts.

In general, Soundness project names are always chosen with some rationale, however it is usually frivolous. Each name is chosen for more for its uniqueness and intrigue than its concision or catchiness, and there is no bias towards names with positive or "nice" meanings—since many of the libraries perform some quite unpleasant tasks.

Names should be English words, though many are obscure or archaic, and it should be noted how willingly English adopts foreign words. Names are generally of Greek or Latin origin, and have often arrived in English via a romance language.

The logo represents a ball of wool, potentially merino wool.

Merino jawn is copyright © 2024 Jon Pretty & Propensive OÜ, and is made available under the Apache 2.0 License.