Fix logic for checking if text blocks are already deindented

core/src/main/java/com/google/googlejavaformat/java/StringWrapper.java

@@ -207,7 +207,8 @@ private void indentTextBlocks(
         String stripped = stripIndent(initialLines.stream().skip(1).collect(joining(separator)));
         ImmutableList<String> lines = stripped.lines().collect(toImmutableList());
         int deindent =
-            initialLines.get(1).stripTrailing().length() - lines.get(0).stripTrailing().length();
+            getLast(initialLines).stripTrailing().length()
+                - getLast(lines).stripTrailing().length();
 
         String prefix =
             (deindent == 0

core/src/test/java/com/google/googlejavaformat/java/StringWrapperTest.java

@@ -174,6 +174,33 @@ public void textBlockSpaceTabMix() throws Exception {
     assertThat(actual).isEqualTo(expected);
   }
 
+  @Test
+  public void leadingBlankLine() throws Exception {
+    assumeTrue(Runtime.version().feature() >= 15);
+    String input =
+        lines(
+            "public class T {",
+            "  String s =",
+            "      \"\"\"",
+            "",
+            "      lorem",
+            "      ipsum",
+            "      \"\"\";",
+            "}");
+    String expected =
+        lines(
+            "public class T {",
+            "  String s =",
+            "      \"\"\"",
+            "",
+            "      lorem",
+            "      ipsum",
+            "      \"\"\";",
+            "}");
+    String actual = StringWrapper.wrap(100, input, new Formatter());
+    assertThat(actual).isEqualTo(expected);
+  }
+
   private static String lines(String... line) {
     return Joiner.on('\n').join(line) + '\n';
   }