Why sbt runs dependency resolution every time after clean?

Question

SBT runs dependency resolution every time after clean even if project dependency management configuration hasn\'t changed. This is time consuming when running o

Answer 1

You can prevent clean from deleting certain files with this setting:

// path should be adapted for newer sbt versions
cleanKeepFiles <+= cacheDirectory / "update"

Answer 2

This works for me on 0.13.1.

cleanKeepFiles ++= Seq("resolution-cache", "streams").map(target.value / _)

Answer 3

Because of directory target/resolution-cache that contains Ivy reports. It is obviously that you remove all target content while clean operation.

IMHO You must point it in your project to somewhere out from target if you want to preserve resolution state.

Updated.

vs SBT.0.12.4.RC1

1. Find where resolution-cache is used - in IvyConfiguration

2. Inspect where IvyConfiguration located - in project scope

   > inspect ivy-configuration
   [info] Task: sbt.IvyConfiguration
   [info] Description:
   [info]  General dependency management (Ivy) settings, such as the resolvers and paths to use.
   [info] Provided by:
   [info]  {file:/home/ezh/projects/sbt/}xsbt/*:ivy-configuration
   [info] Dependencies:
   [info]  xsbt/*:offline
   

3. Fix it in build.sbt.

   ivyConfiguration <<= (ivyConfiguration, baseDirectory) map {
     case (c: InlineIvyConfiguration, b) => import c._
       new InlineIvyConfiguration(paths, resolvers, otherResolvers, moduleConfigurations,
        localOnly, lock, checksums, resolutionCacheDir.map(_ => b / "123"), log)
     case (other, _) => other // something unknown
   }
   

4 Test... Ups... resolution is still active... Investigate. ->

target/scala-2.10/cache/default-920e5d/global/update/output cache contain pointers to resolution-cache :)

1. Fix it.

   cacheDirectory <<= baseDirectory / "234"
   

Test. Got it. Resolution is skipped.

Summary changes for required configuration:

ivyConfiguration <<= (ivyConfiguration, baseDirectory) map {
  case (c: InlineIvyConfiguration, b) => import c._
    new InlineIvyConfiguration(paths, resolvers, otherResolvers, moduleConfigurations,
     localOnly, lock, checksums, resolutionCacheDir.map(_ => b / "123"), log)
  case (other, _) => other // something unknown
}
cacheDirectory <<= baseDirectory / "234"

---

vs SBT.0.13.x

@deprecated("Use the cacheDirectory provided by streams.", "0.13.0")

https://github.com/sbt/sbt/issues/1208

Answer 4

Might be that you have SNAPSHOT dependencies. They are subject to change anytime so must be resolved on every run. You can suppress this with

    offline := true