1 BCE returned as 0 CE in the Japanese calendar

[anba]

Test case:

use icu::calendar::{Calendar, Ref};
use icu::calendar::japanese::Japanese;
use icu::calendar::types::{Era, MonthCode};

use std::str::FromStr;

fn main() {
  let cal = Japanese::new();

  let era = Era::from_str("bce").unwrap(); 
  let monthCode = MonthCode::from_str("M01").unwrap();

  let bce1 = cal.date_from_codes(era, 1, monthCode, 1).unwrap();
  let bce2 = cal.date_from_codes(era, 2, monthCode, 1).unwrap();

  let bce1_year = cal.year(&bce1);
  let bce1_year_era = bce1_year.era;
  println!("BCE 1: {} [{}]", bce1_year.number, format!("{bce1_year_era:?}"));

  let bce2_year = cal.year(&bce2);
  let bce2_year_era = bce2_year.era;
  println!("BCE 2: {} [{}]", bce2_year.number, format!("{bce2_year_era:?}"));

  println!("\n\n");
  dbg!(bce1);
  dbg!(bce2);
}

Prints:

BCE 1: 0 [Era("ce")]
BCE 2: 2 [Era("bce")]

But expected is BCE 1: 1 [Era("bce")].

[anba]

This is possibly caused by this line:

icu4x/components/calendar/src/japanese.rs

Line 668 in 7449b83

if date.year < 0 {

Changing the condition to date.year <= 0 may be sufficient to fix this.

[sffc]

Yes I think the one-liner change is probably correct. Thanks for spotting this!

[sffc]

icu_calendar version 1.5.1 has been released with this fix