Fix optionals to properly error on invalid qualification

conformance/src/test/java/dev/cel/conformance/BUILD.bazel

@@ -175,8 +175,6 @@ _TESTS_TO_SKIP_PLANNER = [
     "timestamps/timestamp_range/sub_time_duration_under",
 
     # Skip until fixed.
-    "optionals/optionals/map_null_entry_no_such_key",
-    "optionals/optionals/map_present_key_invalid_field",
     "parse/receiver_function_names",
     "proto2/extensions_get/package_scoped_test_all_types_ext",
     "proto2/extensions_get/package_scoped_repeated_test_all_types",

runtime/src/main/java/dev/cel/runtime/planner/StringQualifier.java

@@ -15,6 +15,7 @@
 package dev.cel.runtime.planner;
 
 import dev.cel.common.exceptions.CelAttributeNotFoundException;
+import dev.cel.common.values.OptionalValue;
 import dev.cel.common.values.SelectableValue;
 import java.util.Map;
 
@@ -31,21 +32,34 @@ public String value() {
   @Override
   @SuppressWarnings("unchecked") // Qualifications on maps/structs must be a string
   public Object qualify(Object obj) {
+    if (obj instanceof OptionalValue) {
+      OptionalValue<?, ?> opt = (OptionalValue<?, ?>) obj;
+      if (!opt.isZeroValue()) {
+        Object inner = opt.value();
+        if (!(inner instanceof SelectableValue) && !(inner instanceof Map)) {
+          throw CelAttributeNotFoundException.forFieldResolution(value);
+        }
+      }
+    }
+
     if (obj instanceof SelectableValue) {
       return ((SelectableValue<String>) obj).select(value);
-    } else if (obj instanceof Map) {
-      Map<String, Object> map = (Map<String, Object>) obj;
-      if (!map.containsKey(value)) {
-        throw CelAttributeNotFoundException.forMissingMapKey(value);
-      }
+    }
 
+    if (obj instanceof Map) {
+      Map<?, ?> map = (Map<?, ?>) obj;
       Object mapVal = map.get(value);
 
-      if (mapVal == null) {
-        throw CelAttributeNotFoundException.of(
-            String.format("Map value cannot be null for key: %s", value));
+      if (mapVal != null) {
+        return mapVal;
+      }
+
+      if (!map.containsKey(value)) {
+        throw CelAttributeNotFoundException.forMissingMapKey(value);
       }
-      return map.get(value);
+
+      throw CelAttributeNotFoundException.of(
+          String.format("Map value cannot be null for key: %s", value));
     }
 
     throw CelAttributeNotFoundException.forFieldResolution(value);