And some more tests

Author: shmuelhanoch

docs/reference/query-languages/esql/_snippets/functions/types/to_string.md

@@ -78,6 +78,7 @@
 import org.elasticsearch.xpack.esql.expression.function.scalar.convert.ToCartesianShape;
 import org.elasticsearch.xpack.esql.expression.function.scalar.convert.ToDateNanos;
 import org.elasticsearch.xpack.esql.expression.function.scalar.convert.ToDatePeriod;
+import org.elasticsearch.xpack.esql.expression.function.scalar.convert.ToDateRange;
 import org.elasticsearch.xpack.esql.expression.function.scalar.convert.ToDatetime;
 import org.elasticsearch.xpack.esql.expression.function.scalar.convert.ToDegrees;
 import org.elasticsearch.xpack.esql.expression.function.scalar.convert.ToDenseVector;
@@ -470,6 +471,7 @@ private static FunctionDefinition[][] functions() {
                 def(ToDatePeriod.class, ToDatePeriod::new, "to_dateperiod"),
                 def(ToDatetime.class, ToDatetime::new, "to_datetime", "to_dt"),
                 def(ToDateNanos.class, ToDateNanos::new, "to_date_nanos", "to_datenanos"),
+                def(ToDateRange.class, ToDateRange::new, "to_date_range", "to_daterange"),
                 def(ToDegrees.class, ToDegrees::new, "to_degrees"),
                 def(ToDenseVector.class, ToDenseVector::new, "to_dense_vector"),
                 def(ToDouble.class, ToDouble::new, "to_double", "to_dbl"),

docs/reference/query-languages/esql/kibana/definition/functions/to_string.json

@@ -113,7 +113,8 @@ public ToString(
                 "long",
                 "text",
                 "unsigned_long",
-                "version" },
+                "version",
+                "date_range" },
             description = "Input value. The input can be a single- or multi-valued column or an expression."
         ) Expression v
     ) {

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/expression/function/EsqlFunctionRegistry.java

@@ -1641,8 +1641,9 @@ public void testRegexOnInt() {
 
     public void testUnsupportedTypesWithToString() {
         // DATE_PERIOD and TIME_DURATION types have been added, but not really patched through the engine; i.e. supported.
-        final String supportedTypes = "aggregate_metric_double or boolean or cartesian_point or cartesian_shape or date_nanos or datetime "
-            + "or dense_vector or geo_point or geo_shape or geohash or geohex or geotile or ip or numeric or string or version";
+        final String supportedTypes =
+            "aggregate_metric_double or boolean or cartesian_point or cartesian_shape or date_nanos or date_range or datetime "
+                + "or dense_vector or geo_point or geo_shape or geohash or geohex or geotile or ip or numeric or string or version";
         verifyUnsupported(
             "row period = 1 year | eval to_string(period)",
             "line 1:28: argument of [to_string(period)] must be [" + supportedTypes + "], found value [period] type [date_period]"

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/expression/function/scalar/convert/ToString.java

@@ -38,8 +38,8 @@ protected Matcher<String> expectedTypeErrorMatcher(List<Set<DataType>> validPerP
                 "first argument of ["
                     + sourceForSignature(signature)
                     + "] must be [any type except counter types, dense_vector,"
-                    + " aggregate_metric_double, dense_vector or date_range], found value [] type ["
-                    + signature.getFirst()
+                    + " aggregate_metric_double or date_range], found value [] type ["
+                    + signature.getFirst().esType()
                     + "]"
             );
         }