alhudz commented on code in PR #1800:
URL: https://github.com/apache/commons-lang/pull/1800#discussion_r4178006980
##########
src/main/java/org/apache/commons/lang3/time/FastDatePrinter.java:
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@@ -1285,6 +1288,35 @@ public StringBuffer format(final Object obj, final
StringBuffer toAppendTo, fina
throw new IllegalArgumentException("Unknown class: " +
ClassUtils.getName(obj, "<null>"));
}
+ /**
+ * Gets the era names for the calendar this printer formats with.
+ * <p>
+ * {@link DateFormatSymbols#getEras()} only knows the two Gregorian eras.
A locale whose default calendar is not Gregorian, like the Thai Buddhist or
+ * Japanese Imperial calendar, prints that calendar's year, so the era
names have to come from that calendar as well, as {@link SimpleDateFormat} and
+ * {@link FastDateParser} do. The Japanese Imperial calendar also has more
than two eras, so indexing the Gregorian names by its era value would throw an
+ * {@link ArrayIndexOutOfBoundsException}.
+ * </p>
+ *
+ * @param symbols the date format symbols for this printer's locale.
+ * @param style {@link Calendar#SHORT} or {@link Calendar#LONG}.
+ * @return the era names, indexed by the {@link Calendar#ERA} value.
+ */
+ private String[] getEras(final DateFormatSymbols symbols, final int style)
{
+ final Calendar calendar = newCalendar();
+ // The Buddhist calendar extends GregorianCalendar, so test the
calendar type rather than the class.
+ if ("gregory".equals(calendar.getCalendarType())) {
+ return symbols.getEras();
+ }
+ final Map<String, Integer> displayNames =
calendar.getDisplayNames(Calendar.ERA, style, locale);
+ if (displayNames == null) {
+ return symbols.getEras();
+ }
+ final String[] eras = new String[calendar.getMaximum(Calendar.ERA) +
1];
+ Arrays.fill(eras, StringUtils.EMPTY);
+ displayNames.forEach((name, era) -> eras[era] = name);
Review Comment:
Confirmed. The table was picked from the printer's locale alone, while
`format(Calendar)` keeps the caller's calendar.
Repro:
```java
final Calendar gregorian = Calendar.getInstance(TimeZones.GMT, Locale.US);
gregorian.clear();
gregorian.set(2024, Calendar.MAY, 1);
FastDateFormat.getInstance("G", TimeZones.GMT, new Locale("ja", "JP",
"JP")).format(gregorian);
```
Expected: `西暦`
Actual: `明治`; a `th_TH` printer gave `พ.ศ.` for the same calendar where it
should give `ค.ศ.`.
Fix: 3808d5d replaces the `TextField` era rule with an `EraField` rule that
picks the name by the type of the calendar being formatted. The locale's own
calendar still uses the prebuilt table, a Gregorian calendar keeps
`DateFormatSymbols.getEras()`, and a calendar of any other type is asked for
its own name through `Calendar.getDisplayName`, as `SimpleDateFormat` does. The
lookups are bounds checked, so a Japanese Imperial calendar on an `en_US`
printer prints `Reiwa` where it threw `ArrayIndexOutOfBoundsException` before.
`testEraMixedCalendarTypes` runs Gregorian, Buddhist and Japanese Imperial
calendars through `en_US`, `th_TH` and `ja_JP_JP` printers with
`SimpleDateFormat` as the reference. It fails on the previous commit with
`en_US buddhist G ==> expected: <BE> but was: <AD>`.
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