Fix(#291): InstantDeserializer fails to parse negative numeric timest…

…amp strings for pre-1970 values (#362)

datetime/src/main/java/com/fasterxml/jackson/datatype/jsr310/deser/InstantDeserializer.java

@@ -44,6 +44,8 @@
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 
+import static com.fasterxml.jackson.core.json.JsonReadFeature.ALLOW_LEADING_PLUS_SIGN_FOR_NUMBERS;
+
 /**
  * Deserializer for Java 8 temporal {@link Instant}s, {@link OffsetDateTime},
  * and {@link ZonedDateTime}s.
@@ -380,11 +382,16 @@ protected boolean shouldReadTimestampsAsNanoseconds(DeserializationContext conte
     }
 
     // Helper method to find Strings of form "all digits" and "digits-comma-digits"
-    protected int _countPeriods(String str)
+    protected int _countPeriods(String str, boolean allowLeadingPlusSign)
     {
         int commas = 0;
-        for (int i = 0, end = str.length(); i < end; ++i) {
-            int ch = str.charAt(i);
+        int i = 0;
+        int ch = str.charAt(i);
+        if (ch == '-' || (ch == '+' && allowLeadingPlusSign)) {
+            ++i;
+        }
+        for (int end = str.length(); i < end; ++i) {
+            ch = str.charAt(i);
             if (ch < '0' || ch > '9') {
                 if (ch == '.') {
                     ++commas;
@@ -413,7 +420,7 @@ protected T _fromString(JsonParser p, DeserializationContext ctxt,
                 _formatter == DateTimeFormatter.ISO_ZONED_DATE_TIME
             ) {
             // 22-Jan-2016, [datatype-jsr310#16]: Allow quoted numbers too
-            int dots = _countPeriods(string);
+            int dots = _countPeriods(string, p.isEnabled(ALLOW_LEADING_PLUS_SIGN_FOR_NUMBERS.mappedFeature()));
             if (dots >= 0) { // negative if not simple number
                 try {
                     if (dots == 0) {

datetime/src/test/java/com/fasterxml/jackson/datatype/jsr310/deser/InstantDeser291Test.java

@@ -0,0 +1,77 @@
+package com.fasterxml.jackson.datatype.jsr310.deser;
+
+import java.time.Instant;
+import java.util.Locale;
+
+import org.junit.Test;
+
+import com.fasterxml.jackson.core.json.JsonReadFeature;
+import com.fasterxml.jackson.databind.ObjectReader;
+import com.fasterxml.jackson.databind.exc.InvalidFormatException;
+import com.fasterxml.jackson.databind.json.JsonMapper;
+import com.fasterxml.jackson.datatype.jsr310.JavaTimeFeature;
+import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;
+import com.fasterxml.jackson.datatype.jsr310.ModuleTestBase;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertThrows;
+
+// [modules-java8#291] InstantDeserializer fails to parse negative numeric timestamp strings for
+//   pre-1970 values.
+public class InstantDeser291Test 
+    extends ModuleTestBase
+{
+    private final JsonMapper MAPPER = JsonMapper.builder()
+        .defaultLocale(Locale.ENGLISH)
+        .addModule(new JavaTimeModule()
+            .enable(JavaTimeFeature.ALWAYS_ALLOW_STRINGIFIED_DATE_TIMESTAMPS))
+        .build();
+    private final ObjectReader READER = MAPPER.readerFor(Instant.class);
+    private final ObjectReader READER_ALLOW_LEADING_PLUS = READER
+        .withFeatures(JsonReadFeature.ALLOW_LEADING_PLUS_SIGN_FOR_NUMBERS);
+
+    private static final Instant INSTANT_3_SEC_AFTER_EPOC = Instant.ofEpochSecond(3);
+    private static final Instant INSTANT_3_SEC_BEFORE_EPOC = Instant.ofEpochSecond(-3);
+
+    private static final String STR_3_SEC = "\"3.000000000\"";
+    private static final String STR_POSITIVE_3 = "\"+3.000000000\"";
+    private static final String STR_NEGATIVE_3 = "\"-3.000000000\"";
+
+    /**
+     * Baseline that always succeeds, even before resolution of issue 291
+     * @throws Exception
+     */
+    @Test
+    public void testNormalNumericalString() throws Exception {
+        assertEquals(INSTANT_3_SEC_AFTER_EPOC, READER.readValue(STR_3_SEC));
+    }
+
+    /**
+     * Should succeed after issue 291 is resolved.
+     * @throws Exception
+     */
+    @Test
+    public void testNegativeNumericalString() throws Exception {
+        assertEquals(INSTANT_3_SEC_BEFORE_EPOC, READER.readValue(STR_NEGATIVE_3));
+    }
+
+    /**
+     * This should always fail since {@link JsonReadFeature#ALLOW_LEADING_PLUS_SIGN_FOR_NUMBERS} is
+     * not enabled
+     * @throws Exception
+     */
+    @Test
+    public void testPlusSignNumericalString() throws Exception {
+        assertThrows(InvalidFormatException.class, () -> READER.readValue(STR_POSITIVE_3));
+    }
+
+    /**
+     * Should succeed after issue 291 is resolved. Scenario where
+     * {@link JsonReadFeature#ALLOW_LEADING_PLUS_SIGN_FOR_NUMBERS} is enabled
+     * @throws Exception
+     */
+    @Test
+    public void testAllowedPlusSignNumericalString() throws Exception {
+        assertEquals(INSTANT_3_SEC_AFTER_EPOC, READER_ALLOW_LEADING_PLUS.readValue(STR_POSITIVE_3));
+    }
+}