Preserve relative indentation in <pre>{@code ...} blocks lacking leading *.

In classic Javadoc, lines inside `<pre>` blocks that omit the `*` margin prefix
previously had all leading whitespace stripped via `line.stripLeading()`,
destroying relative indentation in code samples.

Instead, strip only up to the comment's base indentation column so that
`JavadocLexer.deindentPreCodeBlocks` can preserve the relative indentation of
the sample.

PiperOrigin-RevId: 994305827

Author: cushon

core/src/main/java/com/google/googlejavaformat/java/javadoc/JavadocFormatter.java

@@ -236,15 +236,29 @@ private static String classicCommentText(String input) {
     // The end result should not strip the `*` from `* foo`.
     List<String> processedLines = new ArrayList<>();
     processedLines.add(lines.get(0));
-    for (String line : lines.subList(1, lines.size())) {
+    List<String> continuations = lines.subList(1, lines.size());
+    int starPrefixLength =
+        continuations.stream()
+            .map(CLASSIC_PREFIX_PATTERN::matcher)
+            .filter(Matcher::find)
+            .mapToInt(Matcher::end)
+            .min()
+            .orElse(0);
+    int nonStarMinLeading =
+        continuations.stream()
+            .filter(line -> !CLASSIC_PREFIX_PATTERN.matcher(line).find())
+            .filter(line -> NOT_SPACE_OR_TAB.matchesAnyOf(line))
+            .mapToInt(NOT_SPACE_OR_TAB::indexIn)
+            .min()
+            .orElse(0);
+    int nonStarStripCount = Math.min(starPrefixLength, nonStarMinLeading);
+    for (String line : continuations) {
       Matcher m = CLASSIC_PREFIX_PATTERN.matcher(line);
       if (m.find()) {
         processedLines.add(m.replaceFirst(""));
       } else {
-        // Input line did not have leading `*`. In that case, it's hard to know what is supposed to
-        // be indentation of the comment as a whole and what is supposed to be indentation of the
-        // content. We just strip all leading whitespace.
-        processedLines.add(line.stripLeading());
+        processedLines.add(
+            line.length() >= nonStarStripCount ? line.substring(nonStarStripCount) : "");
       }
     }
     // Unlike Markdown comments, stripping common leading whitespace is not mandated by any

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

@@ -2534,6 +2534,43 @@ class Test {}
     doFormatTest(input, expected);
   }
 
+  @Test
+  public void preCodeWithoutLeadingStarPreservesIndent() {
+    String input =
+        """
+        /**
+         * <pre>{@code
+        class Demo {
+          // Comment
+          static final int X = 1;
+
+          public static void example() {
+            int y = 2;
+          }
+        }
+         * }</pre>
+         */
+        class Test {}
+        """;
+    String expected =
+        """
+        /**
+         * <pre>{@code
+         * class Demo {
+         *   // Comment
+         *   static final int X = 1;
+         *
+         *   public static void example() {
+         *     int y = 2;
+         *   }
+         * }
+         * }</pre>
+         */
+        class Test {}
+        """;
+    doFormatTest(input, expected);
+  }
+
   // TODO: b/346668798 - Test the following Markdown constructs, and make the tests work as needed.
   // We can assume that the CommonMark parser correctly handles Markdown, so the question is whether
   // they are subsequently mishandled by our formatting logic. So for example the CommonMark parser