[java] TextBlockJoinLinesHandler: fix end offset when converting to a regular literal (IDEA-349062)

GitOrigin-RevId: 752ffd98eefb9d7634a0bd3f78f9a47cb51ba945

java/java-impl/src/com/intellij/codeInsight/editorActions/TextBlockJoinLinesHandler.java

@@ -56,16 +56,17 @@ public final class TextBlockJoinLinesHandler implements JoinRawLinesHandlerDeleg
     boolean fromStartTillEnd = atStartLine && tokenType.equals(JavaTokenType.TEXT_BLOCK_LITERAL) && 
                                doc.getLineNumber(tokenRange.getEndOffset()) == lineNumber + 1 &&
                                token.getText().endsWith("\"\"\"");
+    int endOffset = tokenRange.getEndOffset();
     if (singleSlash || atEmptyStartLine) {
       doc.deleteString(start, end);
-      end = start;
+      endOffset += start - end;
     } else {
       doc.replaceString(start, end, "\\n");
-      end = start + 2;
+      endOffset += start - end + 2;
     }
     if (fromStartTillEnd) {
-      doc.replaceString(tokenRange.getStartOffset(), end + 3, 
-                        convertToRegular(doc.getText().substring(tokenRange.getStartOffset(), end + 3)));
+      doc.replaceString(tokenRange.getStartOffset(), endOffset, 
+                        convertToRegular(doc.getText().substring(tokenRange.getStartOffset(), endOffset)));
     }
     return start;
   }

java/java-tests/testData/codeInsight/joinLines/JoinTextBlockAtStartLineComplete2.java

@@ -0,0 +1,7 @@
+class A {
+  void test() {
+    String s = <selection>"""
+      Line1
+      Line2"""</selection>;
+  }
+}

java/java-tests/testData/codeInsight/joinLines/JoinTextBlockAtStartLineComplete2_after.java

@@ -0,0 +1,5 @@
+class A {
+  void test() {
+    String s = "Line1\nLine2";
+  }
+}

java/java-tests/testSrc/com/intellij/java/codeInsight/JoinLinesTest.java

@@ -303,6 +303,7 @@ public class JoinLinesTest extends LightJavaCodeInsightTestCase {
   public void testJoinTextBlockAtStartLineNonEmpty() {doTest();}
   public void testJoinTextBlockAtStartLineFinalStep() {doTest();}
   public void testJoinTextBlockAtStartLineComplete() {doTest();}
+  public void testJoinTextBlockAtStartLineComplete2() {doTest();}
   public void testJoinTextBlockAtStartLineCompleteWithEscapes() {doTest();}
   public void testJoinTextBlockBackSlash() {doTest();}
   public void testJoinTextBlockBackSlash2() {doTest();}