[7.x] Allow partial parsing dates (#47872) backport(#46814)

Enable partial parsing of date part. This is making the behaviour in java.time implementation the same as with joda.
2018, 2018-01 and 2018-01-01 are all valid dates for date_optional_time or strict_date_optional_time
closes #45284
closes #47473

server/src/main/java/org/elasticsearch/common/time/DateFormatters.java

@@ -59,10 +59,14 @@ public class DateFormatters {
 
     private static final DateTimeFormatter STRICT_YEAR_MONTH_DAY_FORMATTER = new DateTimeFormatterBuilder()
         .appendValue(ChronoField.YEAR, 4, 10, SignStyle.EXCEEDS_PAD)
+        .optionalStart()
         .appendLiteral("-")
         .appendValue(MONTH_OF_YEAR, 2, 2, SignStyle.NOT_NEGATIVE)
+        .optionalStart()
         .appendLiteral('-')
         .appendValue(DAY_OF_MONTH, 2, 2, SignStyle.NOT_NEGATIVE)
+        .optionalEnd()
+        .optionalEnd()
         .toFormatter(Locale.ROOT);
 
     private static final DateTimeFormatter STRICT_HOUR_MINUTE_SECOND_FORMATTER = new DateTimeFormatterBuilder()
@@ -910,12 +914,14 @@ public class DateFormatters {
 
     private static final DateTimeFormatter DATE_FORMATTER = new DateTimeFormatterBuilder()
         .appendValue(ChronoField.YEAR, 1, 5, SignStyle.NORMAL)
+        .optionalStart()
         .appendLiteral('-')
         .appendValue(MONTH_OF_YEAR, 1, 2, SignStyle.NOT_NEGATIVE)
         .optionalStart()
         .appendLiteral('-')
         .appendValue(DAY_OF_MONTH, 1, 2, SignStyle.NOT_NEGATIVE)
         .optionalEnd()
+        .optionalEnd()
         .toFormatter(Locale.ROOT);
 
     private static final DateTimeFormatter HOUR_MINUTE_FORMATTER = new DateTimeFormatterBuilder()

server/src/test/java/org/elasticsearch/common/joda/JavaJodaTimeDuellingTests.java

@@ -38,10 +38,37 @@ import java.time.temporal.TemporalAccessor;
 import java.util.Locale;
 
 import static org.hamcrest.Matchers.containsString;
-import static org.hamcrest.Matchers.equalTo;
 import static org.hamcrest.Matchers.is;
+import static org.hamcrest.core.IsEqual.equalTo;
 
 public class JavaJodaTimeDuellingTests extends ESTestCase {
+    @Override
+    protected boolean enableWarningsCheck() {
+        return false;
+    }
+    // date_optional part of a parser names "strict_date_optional_time" or "date_optional"time
+    // means that date part can be partially parsed.
+    public void testPartialParsing() {
+        assertSameDateAs("2001", "strict_date_optional_time_nanos", "strict_date_optional_time");
+        assertSameDateAs("2001-01", "strict_date_optional_time_nanos", "strict_date_optional_time");
+        assertSameDateAs("2001-01-01", "strict_date_optional_time_nanos", "strict_date_optional_time");
+
+        assertSameDate("2001", "strict_date_optional_time");
+        assertSameDate("2001-01", "strict_date_optional_time");
+        assertSameDate("2001-01-01", "strict_date_optional_time");
+
+        assertSameDate("2001", "date_optional_time");
+        assertSameDate("2001-01", "date_optional_time");
+        assertSameDate("2001-01-01", "date_optional_time");
+
+
+        assertSameDateAs("2001", "iso8601", "strict_date_optional_time");
+        assertSameDateAs("2001-01", "iso8601", "strict_date_optional_time");
+        assertSameDateAs("2001-01-01", "iso8601", "strict_date_optional_time");
+
+        assertSameDate("9999","date_optional_time||epoch_second");
+    }
+
     public void testCompositeDateMathParsing(){
         //in all these examples the second pattern will be used
         assertDateMathEquals("2014-06-06T12:01:02.123", "yyyy-MM-dd'T'HH:mm:ss||yyyy-MM-dd'T'HH:mm:ss.SSS");
@@ -909,4 +936,10 @@ public class JavaJodaTimeDuellingTests extends ESTestCase {
 
         assertEquals(gotMillisJoda, gotMillisJava);
     }
+
+    private void assertSameDateAs(String input, String javaPattern, String jodaPattern) {
+        DateFormatter javaFormatter = DateFormatter.forPattern(javaPattern);
+        DateFormatter jodaFormatter = Joda.forPattern(jodaPattern);
+        assertSameDate(input, javaPattern, jodaFormatter, javaFormatter);
+    }
 }

server/src/test/java/org/elasticsearch/common/time/JavaDateMathParserTests.java

@@ -258,10 +258,11 @@ public class JavaDateMathParserTests extends ESTestCase {
         long datetime = parser.parse("1418248078", () -> 0).toEpochMilli();
         assertDateEquals(datetime, "1418248078", "2014-12-10T21:47:58.000");
 
-        // a timestamp before 10000 is a year
+        // a timestamp before 100000 is a year
-        assertDateMathEquals("9999", "1970-01-01T00:00:09.999Z");
+        assertDateMathEquals("9999", "9999-01-01T00:00:00.000");
-        // 10000 is also a year, breaking bwc, used to be a timestamp
+        assertDateMathEquals("10000", "10000-01-01T00:00:00.000");
-        assertDateMathEquals("10000", "1970-01-01T00:00:10.000Z");
+        assertDateMathEquals("100000", "1970-01-01T00:01:40.000");
+
         // but 10000 with T is still a date format
         assertDateMathEquals("10000-01-01T", "10000-01-01T00:00:00.000");
     }