From 0d7584ffdd20e120ba29232d0f11b85f637c6e22 Mon Sep 17 00:00:00 2001
From: Albert Meltzer <ameltzer@liftoff.io>
Date: Sat, 17 Feb 2024 10:48:06 -0800
Subject: [PATCH] FormatTests: improve idempotency and other errors

---
 .../test/scala/org/scalafmt/FormatTests.scala | 67 ++++++++++++-------
 1 file changed, 41 insertions(+), 26 deletions(-)

diff --git a/scalafmt-tests/src/test/scala/org/scalafmt/FormatTests.scala b/scalafmt-tests/src/test/scala/org/scalafmt/FormatTests.scala
index 5a7170940e..f025c00742 100644
--- a/scalafmt-tests/src/test/scala/org/scalafmt/FormatTests.scala
+++ b/scalafmt-tests/src/test/scala/org/scalafmt/FormatTests.scala
@@ -3,6 +3,9 @@ package org.scalafmt
 import java.io.File
 
 import munit.FunSuite
+import munit.internal.console.AnsiColors
+import munit.internal.difflib.Diff
+
 import org.scalafmt.Error.{Incomplete, SearchStateExploded}
 import org.scalafmt.rewrite.FormatTokensRewrite
 import org.scalafmt.sysops.FileOps
@@ -45,19 +48,22 @@ class FormatTests extends FunSuite with CanRunTests with FormatAssertions {
       filename = t.filename
     )
     debug.printTest()
-    val obtained = result.formatted match {
-      case Formatted.Failure(e)
-          if t.style.onTestFailure.nonEmpty &&
-            e.getMessage.contains(t.style.onTestFailure) =>
-        t.expected
-      case Formatted.Failure(e: Incomplete) => e.formattedCode
-      case Formatted.Failure(e: SearchStateExploded) =>
-        logger.elem(e)
-        e.partialOutput
-      case Formatted.Failure(e) => throw FormatException(e, t.original)
-      case Formatted.Success(code) => code
+    val resultEither = result.formatted.toEither
+    val err = t.style.onTestFailure
+    val obtained = resultEither match {
+      case Left(e) if err.nonEmpty && e.getMessage.contains(err) => t.expected
+      case Left(e: Incomplete) => e.formattedCode
+      case Left(e: SearchStateExploded) => logger.elem(e); e.partialOutput
+      case Left(e) => throw FormatException(e, t.original)
+      case Right(code) => code
     }
+    def assertObtained(implicit loc: munit.Location) =
+      assertEquals(obtained, t.expected)
     debugResults += saveResult(t, obtained, debug)
+    if (resultEither.isLeft) {
+      assertObtained
+      return
+    }
     val debug2 = new Debug(onlyOne)
     val result2 = Scalafmt.formatCode(
       obtained,
@@ -66,21 +72,30 @@ class FormatTests extends FunSuite with CanRunTests with FormatAssertions {
     )
     debug2.printTest()
     val result2Either = result2.formatted.toEither
-    def getFormattedAgain(failOK: Boolean) = result2Either match {
-      case Left(e: ParseException) if !failOK =>
-        "test does not parse: " + parseException2Message(e, obtained)
+    result2Either match {
+      case Left(e: ParseException) if !onlyManual =>
+        assertEquals(
+          "test does not parse: " + parseException2Message(e, obtained),
+          t.expected
+        )
       case Left(e) => throw FormatException(e, obtained)
-      case Right(code) => code
-    }
-    val formattedAgain = getFormattedAgain(onlyManual)
-    if (onlyManual)
-      assertEquals(formattedAgain, obtained, "Idempotency violated")
-    else {
-      assertEquals(
-        if (formattedAgain == obtained || result2Either.isLeft) formattedAgain
-        else "Idempotency violated\n" + formattedAgain,
-        t.expected
-      )
+      case Right(code) =>
+        if (onlyManual) {
+          assertEquals(code, obtained, "Idempotency violated")
+          assertObtained
+        } else if (code == obtained)
+          assertObtained
+        else {
+          val diff = new Diff(code, obtained)
+          if (diff.isEmpty) assertObtained
+          else {
+            val report = AnsiColors.filterAnsi(diff.createDiffOnlyReport())
+            val eol = if (report.last == '\n') "" else "\n"
+            val error = "Idempotency violated\n" + report + eol
+            if (error != t.expected)
+              failComparison(error, code, obtained)
+          }
+        }
     }
     if (
       result2Either.isRight &&
@@ -88,7 +103,7 @@ class FormatTests extends FunSuite with CanRunTests with FormatAssertions {
       FormatTokensRewrite.getEnabledFactories(t.style).isEmpty &&
       !t.style.assumeStandardLibraryStripMargin &&
       !FileOps.isMarkdown(t.filename) &&
-      t.style.onTestFailure.isEmpty
+      err.isEmpty
     )
       assertFormatPreservesAst(
         t.filename,