LUCENE-8787: DateRangePrefixTree now parses milliseconds when num digits != 3

lucene/CHANGES.txt

@@ -139,6 +139,10 @@ Improvements
   of codec internals. This enables a per reader configuration if FSTs are on- or off-heap on a
   per field basis (Simon Willnauer)
 
+* LUCENE-8787: spatial-extras DateRangePrefixTree used to only parse ISO-8601 timestamps with 0 or 3
+  digits of milliseconds precision but now parses other lengths (although > 3 not used).
+  (Thomas Lemmé via David Smiley)
+
 Changes in Runtime Behavior
 
 * LUCENE-8671: Load FST off-heap also for ID-like fields if reader is not opened

lucene/spatial-extras/src/java/org/apache/lucene/spatial/prefix/tree/DateRangePrefixTree.java

@@ -504,16 +504,16 @@ public class DateRangePrefixTree extends NumberRangePrefixTree {
       checkDelimeter(str, offset-1, '.');
       //ms:
 
-      cal.set(Calendar.MILLISECOND, Integer.parseInt(str.substring(offset, offset+3)));
+      int maxOffset = lastOffset - offset; // assume remaining is all digits to compute milliseconds
-      offset += 3;//last one, move to next char
+      // we truncate off > millisecond precision (3 digits only)
-      if (lastOffset == offset)
+      int millis = (int) (Integer.parseInt(str.substring(offset, offset + maxOffset)) / Math.pow(10, maxOffset - 3));
-        return cal;
+      cal.set(Calendar.MILLISECOND, millis);
+      return cal;
     } catch (Exception e) {
       ParseException pe = new ParseException("Improperly formatted datetime: "+str, offset);
       pe.initCause(e);
       throw pe;
     }
-    throw new ParseException("Improperly formatted datetime: "+str, offset);
   }
 
   private  void checkDelimeter(String str, int offset, char delim) {

lucene/spatial-extras/src/test/org/apache/lucene/spatial/prefix/tree/DateRangePrefixTreeTest.java

@@ -17,8 +17,11 @@
 package org.apache.lucene.spatial.prefix.tree;
 
 import java.text.ParseException;
+import java.time.Instant;
+import java.time.OffsetDateTime;
 import java.time.ZoneOffset;
 import java.time.ZonedDateTime;
+import java.time.temporal.ChronoField;
 import java.util.Arrays;
 import java.util.Calendar;
 import java.util.GregorianCalendar;
@@ -30,6 +33,8 @@ import org.apache.lucene.util.LuceneTestCase;
 import org.locationtech.spatial4j.shape.Shape;
 import org.locationtech.spatial4j.shape.SpatialRelation;
 
+import static java.time.format.DateTimeFormatter.ISO_DATE_TIME;
+
 public class DateRangePrefixTreeTest extends LuceneTestCase {
 
   @ParametersFactory(argumentFormatting = "calendar=%s")
@@ -113,6 +118,29 @@ public class DateRangePrefixTreeTest extends LuceneTestCase {
     assertEquals(cal, tree.parseCalendar(expectedISO8601));
   }
 
+  public void testParseCalendar() throws ParseException {
+    Instant expected = OffsetDateTime.of(1984, 12, 18, 12, 34, 56, 100000000, ZoneOffset.UTC).toInstant();
+
+    assertEquals(expected, tree.parseCalendar("1984-12-18T12:34:56.1Z").toInstant());
+    assertEquals(expected.with(ChronoField.MILLI_OF_SECOND, 10), tree.parseCalendar("1984-12-18T12:34:56.01Z").toInstant());
+    assertEquals(expected.with(ChronoField.MILLI_OF_SECOND, 1), tree.parseCalendar("1984-12-18T12:34:56.001Z").toInstant());
+    assertEquals(expected, tree.parseCalendar("1984-12-18T12:34:56.1000Z").toInstant());
+    assertEquals(expected, tree.parseCalendar("1984-12-18T12:34:56.100000000Z").toInstant());
+    assertEquals(expected.with(ChronoField.NANO_OF_SECOND, 0), tree.parseCalendar("1984-12-18T12:34:56Z").toInstant());
+    // decimal places are simply cut off as rounding may affect the "seconds" part of the calender which was set before
+    assertEquals(expected.with(ChronoField.MILLI_OF_SECOND, 999), tree.parseCalendar("1984-12-18T12:34:56.9999Z").toInstant());
+
+    assertEquals(expected, tree.parseCalendar("1984-12-18T12:34:56.1").toInstant());
+    assertEquals(expected.with(ChronoField.MILLI_OF_SECOND, 10), tree.parseCalendar("1984-12-18T12:34:56.01").toInstant());
+    assertEquals(expected.with(ChronoField.MILLI_OF_SECOND, 1), tree.parseCalendar("1984-12-18T12:34:56.001").toInstant());
+    assertEquals(expected, tree.parseCalendar("1984-12-18T12:34:56.1000").toInstant());
+    assertEquals(expected, tree.parseCalendar("1984-12-18T12:34:56.100000000").toInstant());
+    assertEquals(expected.with(ChronoField.NANO_OF_SECOND, 0), tree.parseCalendar("1984-12-18T12:34:56").toInstant());
+    assertEquals(expected.with(ChronoField.MILLI_OF_SECOND, 999), tree.parseCalendar("1984-12-18T12:34:56.9999").toInstant());
+    
+    assertEquals(OffsetDateTime.parse("1984-12-18T12:34:56.01Z", ISO_DATE_TIME).get(ChronoField.MILLI_OF_SECOND), 10);
+  }
+
   //copies from DateRangePrefixTree
   private static final int[] CAL_FIELDS = {
       Calendar.YEAR, Calendar.MONTH, Calendar.DAY_OF_MONTH,