1.1.0-M13

March 5, 2019

coursier 1.1.0-M13 was just released.

The most notable changes of this milestone happened in the new high level API, that is nearing completion. A notion of "rules" or constraints is also being added to coursier, and should be described in more detail in a later post.

High level API

This API aims at being as simple to use as the CLI of coursier, while retaining the purity of the former low level API - without all its traps.

For example, one can fetch a few dependencies with

import coursier._

val files = Fetch()
  .addDependencies(
    dep"org.http4s:http4s-dsl_2.12:0.18.22",
    dep"org.tpolecat:doobie-core_2.12:0.6.0"
  )
  .run()

// files: Seq[java.io.File]

It relies on a "builder pattern", not unlike sttp. Numerous parameters can be adjusted by calling other methods before run, such as addRepositories, withResolutionParams, withCache, etc.

run() runs resolutions and downloads artifacts synchronously, but can be substituted by future() or io to run things in the background, via a Future or the IO monad of your choice.

More details can be found in the documentation.

The CLI and the sbt plugins of coursier already rely on this API. In the future, this should ensure that more advanced features, added in the CLI or the sbt plugin of coursier, are available to API users straightaway. It's also easier to evolve this API while retaining binary compatibility.

Rules

Motivated by SCP-20, support for enforcing some "rules" or constraints is being added to coursier. These are a bit similar to those of the Maven enforcer plugin, and allow to emulate the strict conflict manager of Ivy in particular.

While details are still being ironed out, the CLI already accepts rules.

For example, one can require all the jackson modules to have the same version with

$ coursier resolve org.apache.spark:spark-sql_2.12:2.4.0 \
    --rules 'SameVersion(com.fasterxml.jackson.*:jackson-*)'
…
com.fasterxml.jackson.core:jackson-annotations:2.7.9:default
com.fasterxml.jackson.core:jackson-core:2.7.9:default
com.fasterxml.jackson.core:jackson-databind:2.7.9:default
com.fasterxml.jackson.module:jackson-module-paranamer:2.7.9:default
com.fasterxml.jackson.module:jackson-module-scala_2.12:2.7.9:default
…

By default, if a rule doesn't pass, it can try to address the underlying issue. One can instead require resolution to fail, with

$ coursier resolve org.apache.spark:spark-sql_2.12:2.4.0 \
    --rules 'fail:SameVersion(com.fasterxml.jackson.*:jackson-*)'
Resolution error: Unsatisfiable rule …

An upcoming post should describe rules and future plans in more detail.

Coursier

2.1.21

1.1.0-M13

High level API

Rules