era indices

Author: robertbastian

components/calendar/src/any_calendar.rs

@@ -1584,14 +1584,14 @@ mod tests {
     fn japanese() {
         let japanese = AnyCalendar::new(AnyCalendarKind::Japanese);
         let japanese = Ref(&japanese);
-        single_test_roundtrip(japanese, Some(("reiwa", None)), 3, Month::new(3), 1);
-        single_test_roundtrip(japanese, Some(("heisei", None)), 6, Month::new(12), 1);
-        single_test_roundtrip(japanese, Some(("meiji", None)), 10, Month::new(3), 1);
-        single_test_roundtrip(japanese, Some(("ce", None)), 1000, Month::new(3), 1);
+        single_test_roundtrip(japanese, Some(("reiwa", Some(6))), 3, Month::new(3), 1);
+        single_test_roundtrip(japanese, Some(("heisei", Some(5))), 6, Month::new(12), 1);
+        single_test_roundtrip(japanese, Some(("meiji", Some(2))), 10, Month::new(3), 1);
+        single_test_roundtrip(japanese, Some(("ce", Some(1))), 1000, Month::new(3), 1);
         single_test_roundtrip(japanese, None, 1000, Month::new(3), 1);
         single_test_roundtrip(japanese, None, -100, Month::new(3), 1);
         single_test_roundtrip(japanese, None, 2024, Month::new(3), 1);
-        single_test_roundtrip(japanese, Some(("bce", None)), 10, Month::new(3), 1);
+        single_test_roundtrip(japanese, Some(("bce", Some(0))), 10, Month::new(3), 1);
         // Since #6910, the era range is not enforced in try_from_codes
         /*
         single_test_error(

components/calendar/src/cal/japanese.rs

@@ -200,24 +200,27 @@ impl GregorianYears for &'_ Japanese {
     fn era_year_from_extended(&self, year: i32, month: u8, day: u8) -> types::EraYear {
         let date: EraStartDate = EraStartDate { year, month, day };
 
-        if let Some((start, era)) = [self.last_era.expand(), REIWA, HEISEI, SHOWA, TAISHO, MEIJI]
-            .into_iter()
-            .find(|&(start, _)| date >= start && year >= 1873)
+        if let Some((idx, (start, era))) = [
+            (7, self.last_era.expand()),
+            (6, REIWA),
+            (5, HEISEI),
+            (4, SHOWA),
+            (3, TAISHO),
+            (2, MEIJI),
+        ]
+        .into_iter()
+        .skip((self.last_era.year == 0) as usize)
+        .find(|&(_, (start, _))| date >= start && year >= 1873)
         {
             types::EraYear {
                 era,
-                // TODO: return era indices?
-                era_index: None,
+                era_index: Some(idx),
                 year: year - start.year + 1,
                 extended_year: year,
                 ambiguity: types::YearAmbiguity::CenturyRequired,
             }
         } else {
-            types::EraYear {
-                // TODO: return era indices?
-                era_index: None,
-                ..CeBce.era_year_from_extended(year, month, day)
-            }
+            CeBce.era_year_from_extended(year, month, day)
         }
     }