Copilot commented on code in PR #1815:
URL: https://github.com/apache/commons-lang/pull/1815#discussion_r4272437038
##########
src/main/java/org/apache/commons/lang3/time/FastDatePrinter.java:
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@@ -1591,6 +1598,38 @@ protected List<Rule> parsePattern() {
return rules;
}
+ /**
+ * Tests whether the month is the only field in the pattern.
+ * <p>
+ * {@link SimpleDateFormat} formats the text month of such a pattern with
the standalone month names, which in some languages, like the Slavic and Baltic
+ * ones, are a different grammatical form from the names used next to a
day ("{@code MMMM}" alone prints Russian February as nominative
+ * "{@code февраль}" where "{@code d MMMM}" prints genitive "{@code
февраля}").
+ * </p>
+ *
+ * @return Whether the pattern contains exactly one field, the month.
+ */
+ private boolean isMonthOnlyPattern() {
+ final int[] indexRef = new int[1];
+ boolean monthField = false;
+ for (int i = 0; i < pattern.length(); i++) {
+ indexRef[0] = i;
+ final String token = parseToken(pattern, indexRef);
+ i = indexRef[0];
+ if (token.isEmpty()) {
+ break;
+ }
+ final char c = token.charAt(0);
+ if (c == '\'') {
+ continue;
+ }
+ if (c != 'M' || monthField) {
+ return false;
+ }
Review Comment:
`isMonthOnlyPattern()` currently treats any unquoted literal (e.g., space,
hyphen, comma) as “another field” and returns `false`, even though
`SimpleDateFormat` treats non-letter characters as literals and still considers
patterns like `MMMM-` or `MMMM ` to be month-only. To match date-pattern
semantics, ignore tokens that start with non-letter characters (similar to how
quoted literals are ignored) so that both quoted and unquoted literals are
permitted in a month-only pattern.
##########
src/test/java/org/apache/commons/lang3/time/FastDatePrinterTest.java:
##########
@@ -210,6 +214,36 @@ void testEraNonGregorianCalendar() {
}
}
+ /**
+ * Tests that a month-only pattern uses the standalone month names, like
SimpleDateFormat. In some languages, like the Slavic and Baltic ones, they are a
+ * different grammatical form from the names used next to a day: "MMMM"
alone prints Russian February as nominative "февраль" where "d MMMM" prints
+ * genitive "февраля".
+ */
+ @Test
+ void testStandaloneMonthForMonthOnlyPattern() throws ParseException {
+ // SimpleDateFormat forces the standalone form for a month-only
pattern only since Java 9 (JDK-8114833); Java 8 has no such rule.
+ assumeTrue(SystemUtils.isJavaVersionAtLeast(JavaVersion.JAVA_9));
+ final Locale[] locales = { Locale.US, Locale.GERMANY, new
Locale("ru"), new Locale("cs"), new Locale("pl"), new Locale("fi") };
+ // Month-only patterns, with or without literals, use the standalone
form; patterns with another field keep the format form.
+ final String[] patterns = { "MMM", "MMMM", "'m:'MMMM", "MMMM''", "d
MMMM", "MMMM yyyy", "MMM MMM" };
Review Comment:
The test claims month-only patterns “with or without literals” use the
standalone form, but all literal examples here are quoted. Add at least one
month-only pattern containing an unquoted literal (e.g., `MMMM `, `MMMM-`, or
`MMMM,`) to prevent regressions and to validate the intended behavior once
`isMonthOnlyPattern()` is updated to ignore non-letter literal tokens.
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