Join hyphenated words across Javadoc line breaks; no blank lines before a leading block tag

open-java-format/src/main/java/com/palantir/javaformat/java/javadoc/JavadocLexer.java

@@ -388,6 +388,16 @@ private static ImmutableList<Token> joinAdjacentLiteralsAndAdjacentWhitespace(Li
                 continue;
             }
 
+            if (seenWhitespace.indexOf("\n") >= 0
+                    && !hasMultipleNewlines(seenWhitespace.toString())
+                    && isHyphenatedWordEnd(accumulated)
+                    && tokens.peek().getType() == LITERAL
+                    && isWordStart(tokens.peek().getValue())
+                    && !isSuspendedHyphenConjunction(tokens.peek().getValue())) {
+                accumulated.append(tokens.next().getValue());
+                continue;
+            }
+
             output.add(new Token(LITERAL, accumulated.toString()));
             accumulated.setLength(0);
 
@@ -399,13 +409,26 @@ private static ImmutableList<Token> joinAdjacentLiteralsAndAdjacentWhitespace(Li
             // We have another token coming, possibly of type OTHER. Leave it for the next iteration.
         }
 
-        /*
-         * TODO(cpovirk): Another case where we could try to join tokens is if a line ends with
-         * /[^ -]-/, as in "non-\nblocking."
-         */
         return output.build();
     }
 
+    private static boolean isHyphenatedWordEnd(CharSequence cs) {
+        int length = cs.length();
+        return length >= 2 && cs.charAt(length - 1) == '-' && isWordChar(cs.charAt(length - 2));
+    }
+
+    private static boolean isWordChar(char c) {
+        return Character.isLetterOrDigit(c) || c == '_';
+    }
+
+    private static boolean isWordStart(String s) {
+        return !s.isEmpty() && isWordChar(s.charAt(0));
+    }
+
+    private static boolean isSuspendedHyphenConjunction(String s) {
+        return s.equals("and") || s.equals("or");
+    }
+
     /**
      * Where the input has two consecutive line breaks between literals, insert a {@code <p>} tag between the literals.
      *

open-java-format/src/main/java/com/palantir/javaformat/java/javadoc/JavadocWriter.java

@@ -114,9 +114,7 @@ void writeFooterJavadocTagStart(Token token) {
          */
         postWriteModifiedContinuingListCount.reset();
 
-        if (!wroteAnythingSignificant) {
-            // Javadoc consists solely of tags. This is frowned upon in general but OK for @Overrides.
-        } else if (!continuingFooterTag) {
+        if (!continuingFooterTag) {
             // First footer tag after a body tag.
             requestBlankLine();
         } else {
@@ -328,6 +326,12 @@ private void writeToken(Token token) {
             requestNewline();
         }
 
+        if (!wroteAnythingSignificant) {
+            // Nothing precedes the first token but the opening ∕✱✱ and its newline, so no requested
+            // whitespace (e.g., the blank line a <pre> or <ul> asks for) belongs before it.
+            requestedWhitespace = NONE;
+        }
+
         if (requestedWhitespace == BLANK_LINE
                 && (postWriteModifiedContinuingListCount.isPositive() || continuingFooterTag)) {
             /*

open-java-format/src/test/java/com/palantir/javaformat/java/JavadocFormattingTest.java

@@ -1625,4 +1625,90 @@ void preCodeMixedStarAndBareLinesKeepRelativeIndent() {
         };
         doFormatTest(input, expected);
     }
+
+    @Test
+    void hyphenatedLineBreakJoined() {
+        String[] input = {
+            "/**", //
+            " * This calculation requires an infinite-",
+            " * precision number.",
+            " */",
+            "class Test {}",
+        };
+        String[] expected = {
+            "/** This calculation requires an infinite-precision number. */", //
+            "class Test {}",
+        };
+        doFormatTest(input, expected);
+    }
+
+    @Test
+    void suspendedHyphenPreserved() {
+        String[] input = {
+            "/**", //
+            " * Both pre-",
+            " * and post-processing steps.",
+            " */",
+            "class Test {}",
+        };
+        String[] expected = {
+            "/** Both pre- and post-processing steps. */", //
+            "class Test {}",
+        };
+        doFormatTest(input, expected);
+    }
+
+    @Test
+    void hyphenBeforeParagraphBreakNotJoined() {
+        String[] input = {
+            "/**", //
+            " * Ends with a non-",
+            " *",
+            " * blocking paragraph.",
+            " */",
+            "class Test {}",
+        };
+        String[] expected = {
+            "/**", //
+            " * Ends with a non-",
+            " *",
+            " * <p>blocking paragraph.",
+            " */",
+            "class Test {}",
+        };
+        doFormatTest(input, expected);
+    }
+
+    @Test
+    void preBlockAsFirstContentGetsNoBlankLines() {
+        String[] input = {
+            "/**", //
+            " * <pre>{@code",
+            " * class Demo {",
+            " *   int x;",
+            " * }",
+            " * }</pre>",
+            " */",
+            "class Test {}",
+        };
+        doFormatTest(input, input);
+    }
+
+    @Test
+    void listAsFirstContentGetsNoBlankLines() {
+        String[] input = {
+            "/** <ul><li>one <li>two</ul> */", //
+            "class Test {}",
+        };
+        String[] expected = {
+            "/**", //
+            " * <ul>",
+            " *   <li>one",
+            " *   <li>two",
+            " * </ul>",
+            " */",
+            "class Test {}",
+        };
+        doFormatTest(input, expected);
+    }
 }