Scalafix 0.4.0

This release represents a significant milestone for Scalafix. Scalafix no longer runs as a compiler plugin as it did in previous releases. Instead, Scalafix runs now independently from the compiler, and uses the Scalameta Semantic API to query information from the compiler.

New features

• New rule RemoveUnusedImports, by @olafurpg.
• New rule RemoveXmlLiterals, by @allanrenucci.
• New rule NoAutoTupling, by @gabro.
• New rule ExplicitUnit, by @gabro.
• New rule NoValInForComprehension, by @gabro.
• New github: protocol for loading rules, by @gabro.
• Improved scalafix-testkit, by @olafurpg.
• Simplified Rule API. The public API has shrunk down to four types: Rule, Patch, ScalafixConfig and RuleCtx. The type parameters on Rule and RuleCtx have been removed. A single import scalafix._ is enough get started with rules.
• See the Scalameta Semantic API.

Breaking changes

• The scalafix-nsc compiler plugin has been removed in favor of the Scalameta Semantic DB, that is emitted by the Scalameta semanticdb-scalac compiler plugin. This change enables Scalafix rules to run separately from compilation. This means that running scalafix will be much faster, since it no longer requires creating a custom instance of the Scala compiler and re-typechecking an entire project. Scalafix reads all of its inputs from .semanticdb files that are created by the semanticdb-scalac compiler plugin during regular compilation.

• The signature of Rule.rule has been simplified

  // before
  def rule[T](ctx: RuleCtx[T]): Seq[Patch]
  // after
  def rule(ctx: RuleCtx): Patch
  
  // a Seq[Patch] can be converted into Patch with .asPatch
  Seq[Patch]().asPatch: Patch
  

• RuleCtx.mirror has been removed. To write semantic rules, accept SemanticCtx as a constructor parameter instead

  // before
  case object MySemanticRule extends Rule {
    def rule[T](ctx: RuleCtx[T]): Seq[Patch]
  }
  // after
  case class MySemanticRule(index: SemanticdbIndex) extends SemanticRule(index) {
    def rule(ctx: RuleCtx): Patch
  }
  

• scalafix.patch.TreePatch.{AddGlobalImport, RemoveGlobalImport, Replace, ...} have been made private[scalafix]. Instead, use the provided operations on ctx: RuleCtx.

  // before
  TokenPatch.AddGlobalImport(importer"scala.meta._")
  
  // after
  ctx.addGlobalImport(importer"scala.meta._")
  

  The motivation for this change was to statically enforce that a SemanticCtx is in scope during Patch creation. For the full available API of patch operations, see SemanticPatchOps

• The following configuration options have been removed

  imports.removeUnusedImports // replaced by RemoveUnusedImports rule.
  
  // These were wishful thinking, too eagerly merged.
  imports.organizeImports
  imports.expandRelative
  imports.groupByPrefix
  

• scalafix-cli now enabled the --in-place (-i) flag by default. Use --stdout to print to standard output.

• scalafix-testkit no longer reads tests from .source files. Instead, tests are written in regular .scala files that are compiled through sbt or another build tool. See scalafix-testkit for how to use it.

git shortlog -sn --no-merges v0.3.0..v0.4.0 tells us that 4 people contributed to this release:

• Ólafur Páll Geirsson
• Gabriele Petronella
• Allan Renucci
• Matthias Langer