Extract diff module

build.sbt

@@ -214,7 +214,7 @@ lazy val munit = crossProject(JSPlatform, JVMPlatform, NativePlatform)
   .settings(
     sharedSettings,
     Compile / unmanagedSourceDirectories ++=
-      crossBuildingDirectories("munit", "main").value,
+      crossBuildingDirectories("scala-diff", "main").value,
     libraryDependencies ++= List(
       "org.scala-lang" % "scala-reflect" % {
         if (isScala3Setting.value) scala213
@@ -246,6 +246,8 @@ lazy val munit = crossProject(JSPlatform, JVMPlatform, NativePlatform)
     )
   )
   .jvmConfigure(_.dependsOn(junit))
+  .dependsOn(munitDiff)
+
 lazy val munitJVM = munit.jvm
 lazy val munitJS = munit.js
 lazy val munitNative = munit.native
@@ -270,6 +272,28 @@ lazy val plugin = project
   )
   .disablePlugins(MimaPlugin)
 
+lazy val munitDiff = crossProject(JSPlatform, JVMPlatform, NativePlatform)
+  .in(file("scala-diff"))
+  .settings(
+    moduleName := "scala-diff",
+    sharedSettings,
+    libraryDependencies ++= List(
+      "org.scala-lang" % "scala-reflect" % {
+        if (isScala3Setting.value) scala213
+        else scalaVersion.value
+      } % Provided
+    )
+  )
+  .jvmSettings(
+    sharedJVMSettings
+  )
+  .nativeConfigure(sharedNativeConfigure)
+  .nativeSettings(
+    sharedNativeSettings
+  )
+  .jsConfigure(sharedJSConfigure)
+  .jsSettings(sharedJSSettings)
+
 lazy val tests = crossProject(JSPlatform, JVMPlatform, NativePlatform)
   .dependsOn(munit)
   .enablePlugins(BuildInfoPlugin)

munit/js-native/src/main/scala/munit/internal/junitinterface/JUnitReporter.scala

@@ -4,7 +4,7 @@
 
 package munit.internal.junitinterface
 
-import munit.internal.console.AnsiColors
+import munit.diff.console.AnsiColors
 import sbt.testing._
 import munit.internal.PlatformCompat
 

munit/shared/src/main/scala/munit/Assertions.scala

@@ -1,13 +1,16 @@
 package munit
 
-import munit.internal.console.{Lines, Printers, StackTraces}
-import munit.internal.difflib.ComparisonFailExceptionHandler
-import munit.internal.difflib.Diffs
+import munit.internal.console.{Lines, StackTraces}
+import munit.internal.console.Printers
+import munit.diff.Printer
+import munit.Clue
+import munit.Clues
+import munit.diff.EmptyPrinter
 
 import scala.reflect.ClassTag
 import scala.util.control.NonFatal
 import scala.collection.mutable
-import munit.internal.console.AnsiColors
+import munit.diff.console.AnsiColors
 import org.junit.AssumptionViolatedException
 import munit.internal.MacroCompat
 
@@ -54,7 +57,7 @@ trait Assertions extends MacroCompat.CompileErrorMacro {
       Diffs.assertNoDiff(
         obtained,
         expected,
-        ComparisonFailExceptionHandler.fromAssertions(this, Clues.empty),
+        exceptionHandlerFromAssertions(this, Clues.empty),
         munitPrint(clue),
         printObtainedAsStripMargin = true
       )
@@ -291,6 +294,21 @@ trait Assertions extends MacroCompat.CompileErrorMacro {
     )
   }
 
+  private def exceptionHandlerFromAssertions(
+      assertions: Assertions,
+      clues: => Clues
+  ): ComparisonFailExceptionHandler =
+    new ComparisonFailExceptionHandler {
+      def handle(
+          message: String,
+          obtained: String,
+          expected: String,
+          loc: Location
+      ): Nothing = {
+        assertions.failComparison(message, obtained, expected, clues)(loc)
+      }
+    }
+
   private val munitCapturedClues: mutable.ListBuffer[Clue[_]] =
     mutable.ListBuffer.empty
   def munitCaptureClues[T](thunk: => T): (T, Clues) =

munit/shared/src/main/scala/munit/Clue.scala

@@ -12,5 +12,6 @@ class Clue[+T](
 object Clue extends MacroCompat.ClueMacro {
   @deprecated("use fromValue instead", "1.0.0")
   def empty[T](value: T): Clue[T] = fromValue(value)
-  def fromValue[T](value: T): Clue[T] = new Clue("", value, "")
+  def fromValue[T](value: T): Clue[T] =
+    new Clue("", value, "")
 }

munit/shared/src/main/scala/munit/Compare.scala

@@ -1,7 +1,5 @@
 package munit
 
-import munit.internal.difflib.Diffs
-import munit.internal.difflib.ComparisonFailExceptionHandler
 import scala.annotation.implicitNotFound
 
 /**

munit/shared/src/main/scala/munit/ComparisonFailExceptionHandler.scala

@@ -0,0 +1,10 @@
+package munit
+
+trait ComparisonFailExceptionHandler {
+  def handle(
+      message: String,
+      obtained: String,
+      expected: String,
+      location: Location
+  ): Nothing
+}

munit/shared/src/main/scala/munit/Diffs.scala

@@ -0,0 +1,33 @@
+package munit
+
+import munit.diff.Diff
+
+object Diffs {
+
+  def assertNoDiff(
+      obtained: String,
+      expected: String,
+      handler: ComparisonFailExceptionHandler,
+      title: String,
+      printObtainedAsStripMargin: Boolean
+  )(implicit loc: Location): Boolean = {
+    if (obtained.isEmpty && !expected.isEmpty) {
+      val msg =
+        s"""|Obtained empty output!
+            |=> Expected:
+            |$expected""".stripMargin
+      handler.handle(msg, obtained, expected, loc)
+    }
+    val diff = new Diff(obtained, expected)
+    if (diff.isEmpty) true
+    else {
+      handler.handle(
+        diff.createReport(title, printObtainedAsStripMargin),
+        obtained,
+        expected,
+        loc
+      )
+    }
+  }
+
+}

munit/shared/src/main/scala/munit/internal/console/Lines.scala

@@ -44,10 +44,16 @@ class Lines extends Serializable {
           .append(format(location.line - 1))
           .append(slice(0))
           .append('\n')
-          .append(AnsiColors.use(AnsiColors.Reversed))
+          .append(
+            munit.diff.console.AnsiColors
+              .use(munit.diff.console.AnsiColors.Reversed)
+          )
           .append(format(location.line))
           .append(slice(1))
-          .append(AnsiColors.use(AnsiColors.Reset))
+          .append(
+            munit.diff.console.AnsiColors
+              .use(munit.diff.console.AnsiColors.Reset)
+          )
         if (slice.length >= 3)
           out
             .append('\n')

munit/shared/src/main/scala/munit/internal/console/Printers.scala

@@ -1,13 +1,18 @@
 // Adaptation of https://github.com/lihaoyi/PPrint/blob/e6a918c259ed7ae1998bbf58c360334a3f0157ca/pprint/src/pprint/Walker.scala
 package munit.internal.console
 
-import munit.internal.Compat
-import munit.{EmptyPrinter, Location, Printable, Printer}
-
-import scala.annotation.switch
+import munit.Location
+import munit.diff.Printer
+import munit.diff.EmptyPrinter
+import munit.diff.console.{Printers => DiffPrinters}
 import munit.Clues
+import munit.Printable
+import munit.internal.Compat
 
 object Printers {
+
+  import DiffPrinters._
+
   def log(any: Any, printer: Printer = EmptyPrinter)(implicit
       loc: Location
   ): Unit = {
@@ -123,7 +128,7 @@ object Printers {
       }
     }
     loop(any, indent = 0)
-    AnsiColors.filterAnsi(out.toString())
+    munit.diff.console.AnsiColors.filterAnsi(out.toString())
   }
 
   private def printApply[T](
@@ -163,31 +168,6 @@ object Printers {
     }
   }
 
-  private def printString(
-      string: String,
-      out: StringBuilder,
-      printer: Printer
-  ): Unit = {
-    val isMultiline = printer.isMultiline(string)
-    if (isMultiline) {
-      out.append('"')
-      out.append('"')
-      out.append('"')
-      out.append(string)
-      out.append('"')
-      out.append('"')
-      out.append('"')
-    } else {
-      out.append('"')
-      var i = 0
-      while (i < string.length()) {
-        printChar(string.charAt(i), out)
-        i += 1
-      }
-      out.append('"')
-    }
-  }
-
   /**
    * Pretty-prints this string with non-visible characters escaped.
    *
@@ -216,24 +196,4 @@ object Printers {
     out.toString()
   }
 
-  private def printChar(
-      c: Char,
-      sb: StringBuilder,
-      isEscapeUnicode: Boolean = true
-  ): Unit =
-    (c: @switch) match {
-      case '"'  => sb.append("\\\"")
-      case '\\' => sb.append("\\\\")
-      case '\b' => sb.append("\\b")
-      case '\f' => sb.append("\\f")
-      case '\n' => sb.append("\\n")
-      case '\r' => sb.append("\\r")
-      case '\t' => sb.append("\\t")
-      case c =>
-        val isNonReadableAscii = c < ' ' || (c > '~' && isEscapeUnicode)
-        if (isNonReadableAscii && !Character.isLetter(c))
-          sb.append("\\u%04x".format(c.toInt))
-        else sb.append(c)
-    }
-
 }

munit/shared/src/main/scala/munit/internal/difflib/Chunk.scala → scala-diff/shared/src/main/scala/munit/diff/Chunk.scala

@@ -1,4 +1,4 @@
-package munit.internal.difflib
+package munit.diff
 
 import java.util