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Cache Scalafix instances globally #206

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merged 4 commits into from
Oct 1, 2024
Merged

Cache Scalafix instances globally #206

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7d57735
Cache Scalafix instances globally
lolgab Sep 30, 2024
f959deb
Use ConcurrentHashMap for better thread safety
lolgab Sep 30, 2024
c8798c6
Use `compute` to avoid concurrent initialization of the same key
lolgab Sep 30, 2024
617f307
Cache also `withToolClasspath` using two-layered cache
lolgab Sep 30, 2024
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24 changes: 24 additions & 0 deletions mill-scalafix/src/com/goyeau/mill/scalafix/ScalafixCache.scala
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Original file line number Diff line number Diff line change
@@ -0,0 +1,24 @@
package com.goyeau.mill.scalafix

import com.goyeau.mill.scalafix.CoursierUtils
import coursier.core.Repository
import scalafix.interfaces.Scalafix

import java.util.concurrent.ConcurrentHashMap
import scala.jdk.CollectionConverters._
import scala.ref.SoftReference

private[scalafix] object ScalafixCache {

private val cache = new ConcurrentHashMap[(String, Seq[Repository]), SoftReference[Scalafix]]

def getOrElseCreate(scalaVersion: String, repositories: Seq[Repository]) =
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Since repositories is provided, should we have it in the cache key as well?

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We do, don't we?

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oops 🙈 my bad!

cache.get((scalaVersion, repositories)) match {
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Having a blocking method like computeIfAbsent would avoid getting several concurrent initialisations of the same instance on projects with many modules. This helped with sbt, not sure if the threading model is the same with mill.

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That's a great idea!
I used compute since I wanted to keep the SoftReference.

case SoftReference(value) => value
case _ =>
val newResult =
Scalafix.fetchAndClassloadInstance(scalaVersion, repositories.map(CoursierUtils.toApiRepository).asJava)
cache.put((scalaVersion, repositories), SoftReference(newResult))
newResult
}
}
5 changes: 2 additions & 3 deletions mill-scalafix/src/com/goyeau/mill/scalafix/ScalafixModule.scala
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Expand Up @@ -7,7 +7,6 @@ import mill.api.{Logger, PathRef, Result}
import mill.scalalib.{Dep, ScalaModule}
import mill.define.Command

import scalafix.interfaces.Scalafix
import scalafix.interfaces.ScalafixError.*

import scala.compat.java8.OptionConverters.*
Expand Down Expand Up @@ -77,8 +76,8 @@ object ScalafixModule {
wd: os.Path
): Result[Unit] =
if (sources.nonEmpty) {
val scalafix = Scalafix
.fetchAndClassloadInstance(scalaVersion, repositories.map(CoursierUtils.toApiRepository).asJava)
val scalafix = ScalafixCache
.getOrElseCreate(scalaVersion, repositories)
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Potential tweak even further: as I was mentioning no later than yesterday in the docs, only a major.minor version is required, so FWIW you could strip the patch version to maximize cache hit ratio (the instance will be the same for 3.3.3 and 3.3.4).

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That assumption is true now but it might become false in future versions of scalafix. Since it's very rare to use different patch versions in the same build, I wouldn't bother trying to be clever here.

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Totally fair. FTR, that assumption is based on Scala current semver semantics ensuring backward and forward source compatibility for patch releases, but it could indeed change in the future.

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Alternatively, we could use the full scalafix classpath (as PathRefs, either sorted or as Set) as cache key.

.newArguments()
.withParsedArguments(args.asJava)
.withWorkingDirectory(wd.toNIO)
Expand Down
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