[formatter] fix CompositeWhiteSpaceFormattingStrategy::check

GitOrigin-RevId: cdd4b80c1b5b4dda5fc188b998627246b7a2851b

platform/code-style-impl/src/com/intellij/psi/formatter/CompositeWhiteSpaceFormattingStrategy.java

@@ -57,7 +57,7 @@ public class CompositeWhiteSpaceFormattingStrategy implements WhiteSpaceFormatti
         }
       }
       if (offset == oldOffset) {
-        return start;
+        return offset;
       }
     }
     return offset;

platform/platform-tests/testSrc/com/intellij/psi/formatter/CompositeWhiteSpaceFormattingStrategyTest.kt

@@ -0,0 +1,43 @@
+// Copyright 2000-2022 JetBrains s.r.o. and contributors. Use of this source code is governed by the Apache 2.0 license.
+package com.intellij.psi.formatter
+
+import org.junit.Assert
+import org.junit.Before
+import org.junit.Test
+
+class CompositeWhiteSpaceStrategyTest {
+
+  private lateinit var myStrategy: CompositeWhiteSpaceFormattingStrategy
+
+  @Before
+  fun setUp() {
+    myStrategy = CompositeWhiteSpaceFormattingStrategy(listOf(
+      StaticSymbolWhiteSpaceDefinitionStrategy('a', 'c'),
+      StaticSymbolWhiteSpaceDefinitionStrategy('a', 'b')
+    ))
+  }
+
+  @Test
+  fun failOnTheFirstSymbol() {
+    Assert.assertSame(0, myStrategy.check("daaaaa", 0, 2))
+    Assert.assertSame(1, myStrategy.check("adaaaa", 1, 2))
+  }
+
+  @Test
+  fun failInTheMiddle() {
+    Assert.assertSame(1, myStrategy.check("adbc", 0, 3))
+    Assert.assertSame(4, myStrategy.check("cabcdcb", 1, 5))
+  }
+
+  @Test
+  fun failOnTheLastSymbol() {
+    Assert.assertSame(2, myStrategy.check("aad", 0, 3))
+    Assert.assertSame(3, myStrategy.check("caadabd", 1, 4))
+  }
+
+  @Test
+  fun successfulMatch() {
+    Assert.assertSame(3, myStrategy.check("aca", 0, 3))
+    Assert.assertSame(4, myStrategy.check("babcbda", 1, 4))
+  }
+}