Fix date-time#359 (in embedded-in-jackson-3 date/time code) (#5399)

Author: cowtowncoder

release-notes/VERSION

@@ -10,6 +10,8 @@ Versions: 3.x (for earlier see VERSION-2.x)
 #5350: Add `DeserializationFeature.USE_NULL_FOR_MISSING_REFERENCE_VALUES` for
   selecting `null` vs "empty/absent" value when deserializing missing `Optional` value
 #5361: Fix Maven SBOM publishing (worked in 3.0.0-rc4 but not in rc5 or later)
+(date-time)#359: `InstantDeserializer` deserializes the nanosecond portion of
+  fractional negative timestamps incorrectly
 
 3.0.2 (07-Nov-2025)
 

src/main/java/tools/jackson/databind/ext/javatime/deser/InstantDeserializer.java

@@ -395,8 +395,9 @@ protected T _fromDecimal(DeserializationContext context, BigDecimal value)
     {
         FromDecimalArguments args =
             DecimalUtils.extractSecondsAndNanos(value, (s, ns) -> new FromDecimalArguments(s, ns, getZone(context)),
-                    // [modules-java8#337] since 2.19, only Instant needs negative adjustment
-                    true);
+                    // [modules-java8#359] since 2.21, Instant.ofEpochSecond() correctly handles
+                    // negative nanoseconds, so no adjustment needed
+                    false);
         return fromNanoseconds.apply(args);
     }
 

src/main/java/tools/jackson/databind/ext/javatime/util/DecimalUtils.java

@@ -81,6 +81,14 @@ public static String toDecimal(long seconds, int nanoseconds)
      */
     public static BigDecimal toBigDecimal(long seconds, int nanoseconds)
     {
+        // [modules-java8#359] For negative seconds with positive nanos (times before epoch),
+        // we need to compute the proper decimal value: seconds + (nanos / 1_000_000_000)
+        // Example: Instant{epochSecond=-1, nano=999000000} represents -0.001 seconds
+        if (seconds < 0 && nanoseconds > 0) {
+            return BigDecimal.valueOf(seconds)
+                .add(BigDecimal.valueOf(nanoseconds).scaleByPowerOfTen(-9));
+        }
+
         if (nanoseconds == 0L) {
             // 14-Mar-2015, tatu: Let's retain one zero to avoid interpretation
             //    as integral number

…/InstantDeserializerNegative359Test.java …/InstantDeserializerNegative359Test.javasrc/test/java/tools/jackson/databind/ext/javatime/tofix/InstantDeserializerNegative359Test.java renamed to src/test/java/tools/jackson/databind/ext/javatime/deser/InstantDeserializerNegative359Test.java src/test/java/tools/jackson/databind/ext/javatime/tofix/InstantDeserializerNegative359Test.java renamed to src/test/java/tools/jackson/databind/ext/javatime/deser/InstantDeserializerNegative359Test.java

@@ -1,12 +1,11 @@
-package tools.jackson.databind.ext.javatime.tofix;
+package tools.jackson.databind.ext.javatime.deser;
 
 import java.time.Instant;
 
 import org.junit.jupiter.api.Test;
 
 import tools.jackson.databind.ObjectReader;
 import tools.jackson.databind.ext.javatime.DateTimeTestBase;
-import tools.jackson.databind.testutil.failure.JacksonTestFailureExpected;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
 
@@ -18,7 +17,6 @@ public class InstantDeserializerNegative359Test
 {
     private final ObjectReader READER = newMapper().readerFor(Instant.class);
 
-    @JacksonTestFailureExpected
     @Test
     public void testDeserializationAsFloat04()
         throws Exception