Stop breaking line comments at a no-break space

JavaCommentsHelper wraps a line comment that is too long at the last
whitespace before the limit, and CharMatcher.whitespace() counts the
no-break space U+00A0 as whitespace. The continuation line then starts
with "//" and that no-break space. LINE_COMMENT_MISSING_SPACE_PREFIX,
whose \s does not match it, takes that for a comment with no space after
the slashes, so the next run pads it, breaks at the no-break space again
and leaves the padding behind as an empty "//" line. Every run adds one,
and the file never settles (#38, from google/google-java-format#562).

Line comments now break only at breaking whitespace, which leaves out
U+00A0, U+2007 and U+202F: a no-break space is by definition not a place
to break a line. A number grouped with no-break spaces now moves to the
next line whole instead of being cut inside.

The new golden covers both shapes. The 15,747 files of the JDK 21
sources format exactly as before; none of them contains a no-break
space.

Author: abashev

open-java-format/src/main/java/com/palantir/javaformat/java/JavaCommentsHelper.java

@@ -139,8 +139,11 @@ private List<String> wrapLineComments(List<String> lines, int column0) {
             String prefix = lineCommentPrefix(line);
             while (line.length() + column0 > options.maxLineLength()) {
                 int idx = options.maxLineLength() - column0;
-                // only break on whitespace characters, and ignore the leading `// `
-                while (idx >= prefix.length() && !CharMatcher.whitespace().matches(line.charAt(idx))) {
+                // only break on whitespace characters, and ignore the leading `// `. Not on a no-break space
+                // such as U+00A0: the new line would start with `//` and that space, which the next run takes
+                // for a missing space and pads, and then the comment never settles.
+                while (idx >= prefix.length()
+                        && !CharMatcher.breakingWhitespace().matches(line.charAt(idx))) {
                     idx--;
                 }
                 if (idx <= prefix.length()) {

open-java-format/src/test/resources/com/palantir/javaformat/java/testdata/ojf-issue-38-nbsp-line-comment.input

@@ -0,0 +1,7 @@
+class NbspLineComment {
+    // Batches are capped: the importer rejects any upstream export file whose total row count is at or above 1 000 000 000 rows, so split larger files first.
+    int rows;
+
+    //String testString = " thisisnotaHYPERLINKandsoitshouldntbetruncatedinsteaditshouldbedroppedthisisnotaHYPERLINKandsoit \"http://www.example.com/\""
+    String url;
+}

open-java-format/src/test/resources/com/palantir/javaformat/java/testdata/ojf-issue-38-nbsp-line-comment.output

@@ -0,0 +1,10 @@
+class NbspLineComment {
+    // Batches are capped: the importer rejects any upstream export file whose total row count is at or above
+    // 1 000 000 000 rows, so split larger files first.
+    int rows;
+
+    // String testString =
+    // " thisisnotaHYPERLINKandsoitshouldntbetruncatedinsteaditshouldbedroppedthisisnotaHYPERLINKandsoit
+    // \"http://www.example.com/\""
+    String url;
+}