Add tests and update doc

velox/docs/functions/spark/datetime.rst

@@ -282,3 +282,10 @@ These functions support TIMESTAMP and DATE input types.
 .. spark:function:: year(x) -> integer
 
     Returns the year from ``x``.
+
+.. spark:function:: year_of_week(x) -> integer
+
+    Returns the ISO week-numbering year that ``x`` falls in. For example, 2005-01-02 is
+    part of the 53rd week of year 2004, so the result is 2004. Only supports DATE type.
+
+        SELECT year_of_week('2005-01-02'); -- 2004

velox/functions/sparksql/tests/DateTimeFunctionsTest.cpp

@@ -968,5 +968,21 @@ TEST_F(DateTimeFunctionsTest, makeYMInterval) {
       fromYear(-178956971), "Integer overflow in make_ym_interval(-178956971)");
 }
 
+TEST_F(DateTimeFunctionsTest, yearOfWeek) {
+  const auto yearOfWeek = [&](std::optional<int32_t> date) {
+    return evaluateOnce<int64_t, int32_t>("year_of_week(c0)", {date}, {DATE()});
+  };
+  EXPECT_EQ(std::nullopt, yearOfWeek(std::nullopt));
+  EXPECT_EQ(1970, yearOfWeek(0));
+  EXPECT_EQ(1970, yearOfWeek(-1));
+  EXPECT_EQ(1969, yearOfWeek(-4));
+  EXPECT_EQ(1970, yearOfWeek(-3));
+  EXPECT_EQ(1970, yearOfWeek(365));
+  EXPECT_EQ(1970, yearOfWeek(367));
+  EXPECT_EQ(1971, yearOfWeek(368));
+  EXPECT_EQ(2005, yearOfWeek(parseDate("2006-01-01")));
+  EXPECT_EQ(2006, yearOfWeek(parseDate("2006-01-02")));
+}
+
 } // namespace
 } // namespace facebook::velox::functions::sparksql::test