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Rewrite the missing-space rule without a negative lookahead (google-java-format #1460) #104

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Merged
abashev merged 2 commits into from
Oct 4, 2026
Merged

Rewrite the missing-space rule without a negative lookahead (google-java-format #1460) #104

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fa9cdfb
Rewrite the missing-space rule without a negative lookahead
eamonnmcmanus Oct 3, 2026
369d3bb
Merge branch 'main' into gjf-1460-no-lookahead-regex
abashev Oct 3, 2026
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8 changes: 5 additions & 3 deletions open-java-format/src/main/java/com/palantir/javaformat/java/JavaCommentsHelper.java
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Original file line number Diff line number Diff line change
Expand Up @@ -167,10 +167,12 @@ private static boolean isJBangDirective(String text) {
return matcher.lookingAt() && (matcher.group(1) != null || JBANG_DIRECTIVE_NAMES.contains(matcher.group(2)));
}

private static final Pattern LINE_COMMENT_MISSING_SPACE_PREFIX = Pattern.compile("^(//+)[^\\s/]");

// Preserve special `//noinspection` and `//$NON-NLS-x$` comments used by IDEs, which cannot
// contain leading spaces.
private static final Pattern LINE_COMMENT_MISSING_SPACE_PREFIX =
Pattern.compile("^(//+)(?!noinspection|\\$NON-NLS-\\d+\\$)[^\\s/]");
private static final Pattern LINE_COMMENT_NO_SPACE_PREFIX =
Pattern.compile("^//+(noinspection|\\$NON-NLS-\\d+\\$)");

private static String lineCommentPrefix(String line) {
int prefixLength = 0;
Expand All @@ -191,7 +193,7 @@ private List<String> wrapLineComments(List<String> lines, int column0) {
line = CharMatcher.whitespace().trimLeadingFrom(line);
// Add missing leading spaces to line comments: `//foo` -> `// foo`.
Matcher matcher = LINE_COMMENT_MISSING_SPACE_PREFIX.matcher(line);
if (matcher.find()) {
if (matcher.find() && !LINE_COMMENT_NO_SPACE_PREFIX.matcher(line).find()) {
int length = matcher.group(1).length();
line = "/".repeat(length) + " " + line.substring(length);
}
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27 changes: 27 additions & 0 deletions open-java-format/src/test/java/com/palantir/javaformat/java/FormatterTest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -368,6 +368,33 @@ void onlyWrapLineCommentOnWhitespace_noLeadingWhitespace() throws Exception {
+ "}\n");
}

@Test
void lineCommentGetsItsMissingSpaceExceptIdeMarkers() throws Exception {
// `//foo` gets a space after any number of slashes, while the IDE markers `//noinspection` and `//$NON-NLS-n$`
// are recognised by their tools only without one and stay as written.
String input = "class T {\n"
+ " //noinspection unchecked\n"
+ " //$NON-NLS-1$ //$NON-NLS-2$\n"
+ " //$NON-NLS-12$ and more\n"
+ " //foo\n"
+ " ///foo\n"
+ " // bar\n"
+ " // two spaces\n"
+ " void m() {}\n"
+ "}\n";
String expected = "class T {\n"
+ " //noinspection unchecked\n"
+ " //$NON-NLS-1$ //$NON-NLS-2$\n"
+ " //$NON-NLS-12$ and more\n"
+ " // foo\n"
+ " /// foo\n"
+ " // bar\n"
+ " // two spaces\n"
+ " void m() {}\n"
+ "}\n";
assertThat(Formatter.create().formatSource(input)).isEqualTo(expected);
}

@Test
void throwsFormatterException() throws Exception {
assertThatThrownBy(() -> Formatter.create().formatSourceAndFixImports("package foo; public class {"))
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