Add tests for format_datetime() with time zone offsets

Summary:
In the recent time zone support improvements, time zone offset support
was added to the same API used for regular time zones. Hence, functions based
on this API now also support offests. Adding unit tests to ensure
format_datetime() has the expected behavior.

Addresses facebookincubator#10101

Differential Revision: D60430532

velox/functions/prestosql/tests/DateTimeFunctionsTest.cpp

@@ -148,17 +148,6 @@ class DateTimeFunctionsTest : public functions::test::FunctionBaseTest {
     return resultVector->as<SimpleVector<StringView>>()->valueAt(0);
   }
 
-  std::optional<std::string> formatDatetime(
-      std::optional<Timestamp> timestamp,
-      const std::string& format) {
-    auto resultVector = evaluate(
-        "format_datetime(c0, c1)",
-        makeRowVector(
-            {makeNullableFlatVector<Timestamp>({timestamp}),
-             makeNullableFlatVector<std::string>({format})}));
-    return resultVector->as<SimpleVector<StringView>>()->valueAt(0);
-  }
-
   template <typename T>
   std::optional<T> evaluateWithTimestampWithTimezone(
       const std::string& expression,
@@ -2994,6 +2983,12 @@ TEST_F(DateTimeFunctionsTest, parseDatetime) {
 }
 
 TEST_F(DateTimeFunctionsTest, formatDateTime) {
+  const auto formatDatetime = [&](std::optional<Timestamp> timestamp,
+                                  std::optional<std::string> format) {
+    return evaluateOnce<std::string>(
+        "format_datetime(c0, c1)", timestamp, format);
+  };
+
   // era test cases - 'G'
   EXPECT_EQ("AD", formatDatetime(parseTimestamp("1970-01-01"), "G"));
   EXPECT_EQ("BC", formatDatetime(parseTimestamp("-100-01-01"), "G"));
@@ -3248,6 +3243,12 @@ TEST_F(DateTimeFunctionsTest, formatDateTime) {
           parseTimestamp("1970-01-01 02:33:11.5"),
           "G C Y e 'asdfghjklzxcvbnmqwertyuiop' E '' y D M d a K h H k m s S 1234567890\\\"!@#$%^&*()-+`~{}[];:,./ zzzz"));
 
+  disableAdjustTimestampToTimezone();
+  EXPECT_EQ(
+      "1970-01-01 00:00:00",
+      formatDatetime(
+          parseTimestamp("1970-01-01 00:00:00"), "YYYY-MM-dd HH:mm:ss"));
+
   // User format errors or unsupported errors
   EXPECT_THROW(
       formatDatetime(parseTimestamp("1970-01-01"), "x"), VeloxUserError);
@@ -3276,24 +3277,37 @@ TEST_F(DateTimeFunctionsTest, formatDateTimeTimezone) {
             format);
       };
 
-  const auto zeroTs = parseTimestamp("1970-01-01");
-
-  // No timezone set; default to GMT.
+  // UTC explicitly set.
   EXPECT_EQ(
-      "1970-01-01 00:00:00", formatDatetime(zeroTs, "YYYY-MM-dd HH:mm:ss"));
+      "1970-01-01 00:00:00",
+      formatDatetimeWithTimezone(
+          TimestampWithTimezone(0, "UTC"), "YYYY-MM-dd HH:mm:ss"));
 
   // Check that string is adjusted to the timezone set.
   EXPECT_EQ(
       "1970-01-01 05:30:00",
       formatDatetimeWithTimezone(
-          TimestampWithTimezone(zeroTs.toMillis(), "Asia/Kolkata"),
-          "YYYY-MM-dd HH:mm:ss"));
+          TimestampWithTimezone(0, "Asia/Kolkata"), "YYYY-MM-dd HH:mm:ss"));
 
   EXPECT_EQ(
       "1969-12-31 16:00:00",
       formatDatetimeWithTimezone(
-          TimestampWithTimezone(zeroTs.toMillis(), "America/Los_Angeles"),
+          TimestampWithTimezone(0, "America/Los_Angeles"),
           "YYYY-MM-dd HH:mm:ss"));
+
+  // Make sure format_datetime() works with timezone offsets.
+  EXPECT_EQ(
+      "1969-12-31 16:00:00",
+      formatDatetimeWithTimezone(
+          TimestampWithTimezone(0, "-08:00"), "YYYY-MM-dd HH:mm:ss"));
+  EXPECT_EQ(
+      "1969-12-31 23:45:00",
+      formatDatetimeWithTimezone(
+          TimestampWithTimezone(0, "-00:15"), "YYYY-MM-dd HH:mm:ss"));
+  EXPECT_EQ(
+      "1970-01-01 00:07:00",
+      formatDatetimeWithTimezone(
+          TimestampWithTimezone(0, "+00:07"), "YYYY-MM-dd HH:mm:ss"));
 }
 
 TEST_F(DateTimeFunctionsTest, dateFormat) {