Fix sbt output coloring

SBT puts a [info] prefix on the output of the tests framework which resets the color each line, therefore this commits ensures that every line in difflicious rendered string is recolored.

Fixes #6

Author: jatcwang

docs/docs/docs/LibraryIntegrations.md

@@ -34,7 +34,14 @@ Add this to your SBT build
 "com.github.jatcwang" %% "difflicious-scalatest" % "{{ site.version }}" % Test
 ```
 
-and then in your test suites you can call `assertNoDiff` on any `Differ`.
+Tests should be run with the `-oW` option to disable Scalatest from coloring test failures all red as it interferes with 
+difflicious color display.
+
+```
+testOnly -- -oW
+```
+
+Here's an example of what a test using difflicious looks like:
 
 ```scala mdoc:nest
 import org.scalatest.funsuite.AnyFunSuite

modules/core/src/main/scala/difflicious/DiffResultPrinter.scala

@@ -2,7 +2,7 @@ package difflicious
 
 import difflicious.DiffResult.MapResult.Entry
 import difflicious.DiffResult.ValueResult
-import fansi.{Str, Color}
+import fansi.{Color, EscapeAttr, Str}
 
 object DiffResultPrinter {
   private val colorObtained = Color.Red
@@ -29,9 +29,7 @@ object DiffResultPrinter {
         case r: DiffResult.ListResult => {
           val indentForFields = Str("\n" ++ indentLevel.asSpacesPlus1)
           val listStrs = r.items
-            .map { res =>
-              consoleOutput(res, indentLevel + 1) ++ ","
-            }
+            .map { res => consoleOutput(res, indentLevel + 1) ++ "," }
             .foldLeft(Str("")) { case (accum, next) => accum ++ indentForFields ++ next }
           val allStr = Str(s"${r.typeName.short}(") ++ listStrs ++ Str(s"\n${indentLevel.asSpaces})")
           colorOnMatchType(str = allStr, matchType = r.pairType)
@@ -98,14 +96,32 @@ object DiffResultPrinter {
       }
   }
 
+  private val dummyColoSeparator = Str(" ").overlay(Color.Reset)
   private def colorOnMatchType(
     str: Str,
     matchType: PairType,
   ): Str = {
+    // Because SBT (and maybe other tools) put their own logging prefix on each line (e.g. [info])
+    // they effectively resets the color of each line. Therefore we need to ensure every line is "recolored"
+    // Because we always indent with spaces, we do this by recoloring the first space we find on each line.
+    def recolorEachLine(orig: Str, color: EscapeAttr) = {
+      orig.plainText.linesIterator
+        .map { s =>
+          if (s.startsWith(" "))
+            dummyColoSeparator ++ Str(s.drop(1)).overlay(color)
+          else
+            Str(s).overlay(color)
+        }
+        .reduceLeft((accum, next) => accum ++ Str("\n") ++ next)
+    }
+
     matchType match {
-      case PairType.Both         => str
-      case PairType.ObtainedOnly => str.overlay(colorObtained)
-      case PairType.ExpectedOnly => str.overlay(colorExpected)
+      case PairType.Both => str
+      case PairType.ObtainedOnly => {
+        recolorEachLine(str, colorObtained)
+      }
+      case PairType.ExpectedOnly =>
+        recolorEachLine(str, colorExpected)
     }
   }
 

modules/core/src/main/scala/difflicious/differ/TransformedDiffer.scala

@@ -1,9 +1,9 @@
 package difflicious.differ
 
-import difflicious.{DiffResult, ConfigureOp, ConfigureError, ConfigurePath, DiffInput}
+import difflicious.{ConfigureError, ConfigureOp, ConfigurePath, DiffInput, DiffResult}
 
 /**
-  * A Differ that transforms any input of [[diff]] method and pass it to its underlying Differ.
+  * A Differ that transforms any input of diff method and pass it to its underlying Differ.
   * See [[ValueDiffer.contramap]]
   */
 class TransformedDiffer[T, U](underlyingDiffer: ValueDiffer[U], transformFunc: T => U) extends ValueDiffer[T] {

modules/coretest/src/test/scala/difflicious/testutils/package.scala

@@ -3,7 +3,7 @@ package difflicious
 import difflicious.DiffResultPrinter.consoleOutput
 import munit.Assertions.assertEquals
 import org.scalacheck.Prop.{forAll, propBoolean}
-import org.scalacheck.{Prop, Arbitrary}
+import org.scalacheck.{Arbitrary, Prop}
 import difflicious.internal.EitherGetSyntax._
 
 package object testutils {
@@ -51,7 +51,17 @@ package object testutils {
     res: DiffResult,
     expectedOutputStr: String,
   ): Unit = {
-    val obtainedOutputStr = consoleOutput(res, 0).render
+
+    // Reverse "recolor each line" difflicious.DiffResultPrinter.colorOnMatchType
+    // to make test expectations easier to read and write
+    def removeMultilineRecoloring(str: String): String = {
+      val k = s"$X\n $R"
+      val j = s"$X\n $G"
+      val replaced = str.replace(k, "\n ").replace(j, "\n ")
+      replaced
+    }
+
+    val obtainedOutputStr = removeMultilineRecoloring(consoleOutput(res, 0).render)
 
     if (obtainedOutputStr != expectedOutputStr) {
       println("=== Obtained Output === ")