Json4s brings in scalap-2.10.0 dependencies regardless of scalaVersion setting

[mcamou]

With the following build.sbt:

val json4sVersion = "3.2.7"

name := "Json4sDependencies"

organization := "com.tecnoguru"

version := "1.0"

scalaVersion := "2.10.3"

libraryDependencies ++= Seq("org.json4s" %% "json4s-jackson" % json4sVersion,
                            "org.json4s" %% "json4s-ext" % json4sVersion)

I get the following inside SBT:

> show dependencyClasspath
[info] List(Attributed(/Users/mario/.ivy2/cache/org.scala-lang/scala-library/jars/scala-library-2.10.3.jar), Attributed(/Users/mario/.ivy2/cache/org.json4s/json4s-jackson_2.10/jars/json4s-jackson_2.10-3.2.7.jar), Attributed(/Users/mario/.ivy2/cache/org.json4s/json4s-core_2.10/jars/json4s-core_2.10-3.2.7.jar), Attributed(/Users/mario/.ivy2/cache/org.json4s/json4s-ast_2.10/jars/json4s-ast_2.10-3.2.7.jar), Attributed(/Users/mario/.ivy2/cache/com.thoughtworks.paranamer/paranamer/jars/paranamer-2.6.jar), Attributed(/Users/mario/.ivy2/cache/org.scala-lang/scalap/jars/scalap-2.10.0.jar), Attributed(/Users/mario/.ivy2/cache/org.scala-lang/scala-compiler/jars/scala-compiler-2.10.0.jar), Attributed(/Users/mario/.ivy2/cache/org.scala-lang/scala-reflect/jars/scala-reflect-2.10.0.jar), Attributed(/Users/mario/.ivy2/cache/com.fasterxml.jackson.core/jackson-databind/bundles/jackson-databind-2.3.1.jar), Attributed(/Users/mario/.ivy2/cache/com.fasterxml.jackson.core/jackson-annotations/bundles/jackson-annotations-2.3.0.jar), Attributed(/Users/mario/.ivy2/cache/com.fasterxml.jackson.core/jackson-core/bundles/jackson-core-2.3.1.jar), Attributed(/Users/mario/.ivy2/cache/org.json4s/json4s-ext_2.10/jars/json4s-ext_2.10-3.2.7.jar), Attributed(/Users/mario/.ivy2/cache/joda-time/joda-time/jars/joda-time-2.3.jar), Attributed(/Users/mario/.ivy2/cache/org.joda/joda-convert/jars/joda-convert-1.6.jar))
[success] Total time: 0 s, completed Mar 20, 2014 3:18:47 PM

Note the scalap-2.10.0, scala-compiler-2.10.0 and scala-reflect-2.10.0 dependencies. Using the sbt-dependency-graph plugin I've narrowed it down to the scalap dependency. You can work around this by adding an explicit dependency on "org.scala-lang" % "scalap" % scalaVersion.value in your build.sbt but this should really be fixed in Json4s

[casualjim]

You can override this by explicitly depending on scalap for your scala version.

If I want to be certain json4s behaves on all scala 2.10 versions then I need to compile it with 2.10.0 and leave the scala choice up to the user. or I have to publish a json4s version for each scala 2.10 version which is even less desirable I think.

[DavidPerezIngeniero]

I wonder why json4s does need a scala compiler as a runtime dependency.

[casualjim]

because we need to read the byte code to find out information about scala primitives. This is more necessary on 2.9 than it is on 2.10

[DavidPerezIngeniero]

Thanks for your answer.
I've made a question in stackoverflow:
http://stackoverflow.com/questions/24446832/why-does-json4s-need-a-scala-compiler-as-a-runtime-dependency/

[enlait]

This adds about ~18 MB worth of dependencies. 18Mb for working with json. Are you serious?

[casualjim]

I welcome a pull request that makes reflection work otherwise also for 2.9.

[enlait]

Does json4s build for scala 2.11 need reflection to work for 2.9?
I'm sure it's not an easy change, but such a huge dependency can be a show stopper.

[DavidPerezIngeniero]

This dependency is for the native version and also for the jackson version,
as it is included in json4s-core.
It can be seen here:

http://mvnrepository.com/artifact/org.json4s/json4s-core_2.10/3.2.10

2014-07-02 12:49 GMT+02:00 enlait notifications@github.com:

Does json4s build for scala 2.11 need reflection to work for 2.9?
I'm sure it's not an easy change, but such a huge dependency can be a show
stopper.

—
Reply to this email directly or view it on GitHub
#108 (comment).

[jongwook]

Apache Spark uses json4s and this issue broke my scala 2.11 project build.

I had to explicitly exclude scalap and scala-library like

libraryDependencies ++= Seq(
   // dependencies ... 
).map {
    _.exclude("org.scala-lang", "scalap").exclude("org.scala-lang", "scala-library")
}

otherwise sbt gets confused by the scala-library pulled by json4s, and IntelliJ won't even let me open the project.

Is it fixed in 3.3.0?

[seratch]

Is it fixed in 3.3.0?

Yes, it is. This issue doesn't happen in 3.3 because json4s 3.3 has its own scalap fork and doesn't depend on scala-lang's scalap.