Core: Deprecate use of scientific notation in epoch time parsing (#36691)

The joda epoch parsing code currently supports passing epoch time as a
number in scientific notation. However, no systems appear to exist which
output timestamps in scientific notation. In java time, it is
particularly complex to implement scientific notation timestamp parsing
within a DateTimeFormatter. This commit adds a deprecation warning when
the epoch time parsers in joda parse scientific notation, so that it can
be removed when switching to java time.
joda are passed a time in scientific notation.

Author: rjernst

server/src/main/java/org/elasticsearch/common/joda/Joda.java

@@ -47,6 +47,7 @@
 import java.io.Writer;
 import java.math.BigDecimal;
 import java.util.Locale;
+import java.util.regex.Pattern;
 
 public class Joda {
 
@@ -321,6 +322,8 @@ public DateTimeField getField(Chronology chronology) {
 
     public static class EpochTimeParser implements DateTimeParser {
 
+        private static final Pattern scientificNotation = Pattern.compile("[Ee]");
+
         private final boolean hasMilliSecondPrecision;
 
         public EpochTimeParser(boolean hasMilliSecondPrecision) {
@@ -348,6 +351,11 @@ public int parseInto(DateTimeParserBucket bucket, String text, int position) {
             int factor = hasMilliSecondPrecision ? 1 : 1000;
             try {
                 long millis = new BigDecimal(text).longValue() * factor;
+                // check for deprecation, but after it has parsed correctly so the "e" isn't from something else
+                if (scientificNotation.matcher(text).find()) {
+                    deprecationLogger.deprecatedAndMaybeLog("epoch-scientific-notation", "Use of scientific notation" +
+                        "in epoch time formats is deprecated and will not be supported in the next major version of Elasticsearch.");
+                }
                 DateTime dt = new DateTime(millis, DateTimeZone.UTC);
                 bucket.saveField(DateTimeFieldType.year(), dt.getYear());
                 bucket.saveField(DateTimeFieldType.monthOfYear(), dt.getMonthOfYear());

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

@@ -77,13 +77,11 @@ public void testDuellingFormatsValidParsing() {
         assertSameDate("1", "epoch_second");
         assertSameDate("-1", "epoch_second");
         assertSameDate("-1522332219", "epoch_second");
-        assertSameDate("1.0e3", "epoch_second");
         assertSameDate("1522332219321", "epoch_millis");
         assertSameDate("0", "epoch_millis");
         assertSameDate("1", "epoch_millis");
         assertSameDate("-1", "epoch_millis");
         assertSameDate("-1522332219321", "epoch_millis");
-        assertSameDate("1.0e3", "epoch_millis");
 
         assertSameDate("20181126", "basic_date");
         assertSameDate("20181126T121212.123Z", "basic_date_time");

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

@@ -753,6 +753,15 @@ public void testDeprecatedFormatSpecifiers() {
             " next major version of Elasticsearch. Prefix your date format with '8' to use the new specifier.");
     }
 
+    public void testDeprecatedScientificNotation() {
+        assertValidDateFormatParsing("epoch_second", "1.234e5", "123400");
+        assertWarnings("Use of scientific notation" +
+            "in epoch time formats is deprecated and will not be supported in the next major version of Elasticsearch.");
+        assertValidDateFormatParsing("epoch_millis", "1.234e5", "123400");
+        assertWarnings("Use of scientific notation" +
+            "in epoch time formats is deprecated and will not be supported in the next major version of Elasticsearch.");
+    }
+
     private void assertValidDateFormatParsing(String pattern, String dateToParse) {
         assertValidDateFormatParsing(pattern, dateToParse, dateToParse);
     }