Adding mapInsert internal runtime function

checker/src/main/java/dev/cel/checker/CelStandardDeclarations.java

@@ -93,6 +93,8 @@ enum StandardFunction {
         Overload.Arithmetic.ADD_STRING,
         Overload.Arithmetic.ADD_BYTES,
         Overload.Arithmetic.ADD_LIST,
+        Overload.Arithmetic.MAP_INSERT_KEY_VALUE,
+        Overload.Arithmetic.MAP_INSERT_MAP,
         Overload.Arithmetic.ADD_TIMESTAMP_DURATION,
         Overload.Arithmetic.ADD_DURATION_TIMESTAMP,
         Overload.Arithmetic.ADD_DURATION_DURATION),
@@ -410,6 +412,12 @@ public enum Arithmetic implements StandardOverload {
         ADD_LIST(
             CelOverloadDecl.newGlobalOverload(
                 "add_list", "list concatenation", LIST_OF_A, LIST_OF_A, LIST_OF_A)),
+        MAP_INSERT_KEY_VALUE(
+            CelOverloadDecl.newGlobalOverload(
+                "mapInsert_map_key_value", "map insertion", MAP_OF_AB, MAP_OF_AB, TYPE_PARAM_A, TYPE_PARAM_B)),
+        MAP_INSERT_MAP(
+            CelOverloadDecl.newGlobalOverload(
+                "mapInsert_map_map", "map insertion", MAP_OF_AB, MAP_OF_AB, MAP_OF_AB)),
         ADD_TIMESTAMP_DURATION(
             CelOverloadDecl.newGlobalOverload(
                 "add_timestamp_duration",

runtime/src/main/java/dev/cel/runtime/CelStandardFunctions.java

@@ -17,6 +17,7 @@
 import static com.google.common.base.Preconditions.checkNotNull;
 
 import com.google.common.annotations.VisibleForTesting;
+import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableSet;
 import com.google.common.primitives.Ints;
 import com.google.common.primitives.UnsignedLong;
@@ -83,6 +84,8 @@ public enum StandardFunction {
         Arithmetic.ADD_STRING,
         Arithmetic.ADD_BYTES,
         Arithmetic.ADD_LIST,
+        Arithmetic.MAP_INSERT_MAP_MAP,
+        Arithmetic.MAP_INSERT_MAP_KEY_VALUE,
         Arithmetic.ADD_TIMESTAMP_DURATION,
         Arithmetic.ADD_DURATION_TIMESTAMP,
         Arithmetic.ADD_DURATION_DURATION),
@@ -373,6 +376,16 @@ public enum Arithmetic implements StandardOverload {
             (bindingHelper) ->
                 CelFunctionBinding.from(
                     "add_list", List.class, List.class, RuntimeHelpers::concat)),
+        MAP_INSERT_MAP_MAP(
+            (bindingHelper) ->
+                CelFunctionBinding.from(
+                    "mapInsert_map_map", Map.class, Map.class, RuntimeHelpers::mapInsert)),
+        MAP_INSERT_MAP_KEY_VALUE(
+            (bindingHelper) ->
+                CelFunctionBinding.from(
+                    "mapInsert_map_key_value",
+                    ImmutableList.of(Map.class, Object.class, Object.class),
+                    RuntimeHelpers::mapInsert)),
         SUBTRACT_INT64(
             (bindingHelper) ->
                 CelFunctionBinding.from(

runtime/src/main/java/dev/cel/runtime/RuntimeHelpers.java

@@ -30,7 +30,9 @@
 import dev.cel.common.internal.Converter;
 import java.time.format.DateTimeParseException;
 import java.util.ArrayList;
+import java.util.HashMap;
 import java.util.List;
+import java.util.Map;
 import java.util.Optional;
 import org.threeten.extra.AmountFormats;
 
@@ -96,6 +98,31 @@ static <E> List<E> concat(List<E> first, List<E> second) {
     return result;
   }
 
+  /** Concatenates two maps into a new map */
+  static Map<Object, Object> mapInsert(Map<Object, Object> first, Map<Object, Object> second) {
+    // TODO: return a mutable map instead of an actual copy.
+    Map<Object, Object> result = new HashMap<>(first.size() + second.size());
+    result.putAll(first);
+    result.putAll(second);
+    return result;
+  }
+
+  /** Add new key value pair to an existing map. */
+  static Map<Object, Object> mapInsert(Object[] args) {
+    Map<?, ?> map = (Map<?, ?>) args[0];
+    Object key = args[1];
+    Object value = args[2];
+    // TODO: return a mutable map instead of an actual copy.
+    if (map.containsKey(key)) {
+      throw new IllegalArgumentException(
+          String.format("insert failed: key %s already exists", key));
+    }
+    Map<Object, Object> result = new HashMap<>(map.size() + 1);
+    result.putAll(map);
+    result.put(key, value);
+    return result;
+  }
+
   // Collections
   // ===========