Add a warning for when targeting attributes are truncated

src/main/java/org/prebid/server/auction/BidResponseCreator.java

@@ -1565,7 +1565,15 @@ private Bid toBid(BidInfo bidInfo,
             final String categoryDuration = bidInfo.getCategory();
             targetingKeywords = keywordsCreator != null
                     ? keywordsCreator.makeFor(
-                    bid, seat, isWinningBid, cacheId, bidType.getName(), videoCacheId, categoryDuration, account)
+                    bid,
+                    seat,
+                    isWinningBid,
+                    cacheId,
+                    bidType.getName(),
+                    videoCacheId,
+                    categoryDuration,
+                    account,
+                    bidWarnings)
                     : null;
         } else {
             targetingKeywords = null;

src/main/java/org/prebid/server/auction/TargetingKeywordsCreator.java

@@ -2,7 +2,9 @@
 
 import com.iab.openrtb.response.Bid;
 import org.apache.commons.lang3.StringUtils;
+import org.prebid.server.bidder.model.BidderError;
 import org.prebid.server.proto.openrtb.ext.request.ExtPriceGranularity;
+import org.prebid.server.proto.openrtb.ext.response.ExtBidderError;
 import org.prebid.server.settings.model.Account;
 
 import java.math.BigDecimal;
@@ -12,7 +14,6 @@
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
-import java.util.stream.Collectors;
 
 /**
  * Used throughout Prebid to create targeting keys as keys which can be used in an ad server like DFP.
@@ -154,7 +155,8 @@ Map<String, String> makeFor(Bid bid,
                                 String format,
                                 String vastCacheId,
                                 String categoryDuration,
-                                Account account) {
+                                Account account,
+                                Map<String, List<ExtBidderError>> bidWarnings) {
 
         final Map<String, String> keywords = makeFor(
                 bidder,
@@ -170,13 +172,13 @@ Map<String, String> makeFor(Bid bid,
                 account);
 
         if (resolver == null) {
-            return truncateKeys(keywords);
+            return truncateKeys(keywords, bidWarnings);
         }
 
         final Map<String, String> augmentedKeywords = new HashMap<>(keywords);
         augmentedKeywords.putAll(resolver.resolve(bid, bidder));
 
-        return truncateKeys(augmentedKeywords);
+        return truncateKeys(augmentedKeywords, bidWarnings);
     }
 
     /**
@@ -261,12 +263,33 @@ private static String sizeFrom(Integer width, Integer height) {
                 : null;
     }
 
-    private Map<String, String> truncateKeys(Map<String, String> keyValues) {
-        return truncateAttrChars > 0
-                ? keyValues.entrySet().stream()
-                .collect(Collectors
-                        .toMap(keyValue -> truncateKey(keyValue.getKey()), Map.Entry::getValue, (key1, key2) -> key1))
-                : keyValues;
+    private Map<String, String> truncateKeys(Map<String, String> keyValues,
+                                             Map<String, List<ExtBidderError>> bidWarnings) {
+
+        if (truncateAttrChars <= 0) {
+            return keyValues;
+        }
+
+        final Map<String, String> keys = new HashMap<>();
+        final List<String> truncatedKeys = new ArrayList<>();
+        for (Map.Entry<String, String> entry : keyValues.entrySet()) {
+            final String key = entry.getKey();
+            final String truncatedKey = truncateKey(key);
+            keys.putIfAbsent(truncatedKey, entry.getValue());
+
+            if (truncatedKey.length() != key.length()) {
+                truncatedKeys.add(key);
+            }
+        }
+
+        if (!truncatedKeys.isEmpty()) {
+            final String errorMessage = "The following keys have been truncated: %s"
+                    .formatted(String.join(", ", truncatedKeys));
+            bidWarnings.computeIfAbsent("targeting", ignored -> new ArrayList<>())
+                    .add(ExtBidderError.of(BidderError.Type.bad_input.getCode(), errorMessage));
+        }
+
+        return keys;
     }
 
     private String truncateKey(String key) {

src/test/groovy/org/prebid/server/functional/testcontainers/PbsConfig.groovy

@@ -145,5 +145,9 @@ LIMIT 1
          "currency-converter.external-rates.refresh-period-ms" : "900000"]
     }
 
+    static Map<String,String> getTargetingConfig() {
+        ["settings.targeting.truncate-attr-chars": '255']
+    }
+
     private PbsConfig() {}
 }

src/test/groovy/org/prebid/server/functional/testcontainers/container/PrebidServerContainer.groovy

@@ -42,6 +42,7 @@ class PrebidServerContainer extends GenericContainer<PrebidServerContainer> {
                 << PbsConfig.bidderAliasConfig
                 << PbsConfig.prebidCacheConfig
                 << PbsConfig.mySqlConfig
+                << PbsConfig.targetingConfig
         withConfig(commonConfig)
         withConfig(customConfig)
     }

src/test/groovy/org/prebid/server/functional/tests/CacheSpec.groovy

@@ -27,7 +27,6 @@ class CacheSpec extends BaseSpec {
     private static final String PBS_API_HEADER = 'x-pbc-api-key'
     private static final Integer MAX_DATACENTER_REGION_LENGTH = 4
     private static final Integer DEFAULT_UUID_LENGTH = 36
-    private static final Integer TARGETING_PARAM_NAME_MAX_LENGTH = 20
 
     private static final String XML_CREATIVE_SIZE_ACCOUNT_METRIC = "account.%s.prebid_cache.creative_size.xml"
     private static final String JSON_CREATIVE_SIZE_ACCOUNT_METRIC = "account.%s.prebid_cache.creative_size.json"
@@ -612,8 +611,8 @@ class CacheSpec extends BaseSpec {
             it.get("hb_cache_id_generic")
             it.get("hb_cache_path") == CACHE_PATH
             it.get("hb_cache_host") == CACHE_HOST
-            it.get("hb_cache_path_generic".substring(0, TARGETING_PARAM_NAME_MAX_LENGTH)) == CACHE_PATH
-            it.get("hb_cache_host_generic".substring(0, TARGETING_PARAM_NAME_MAX_LENGTH)) == CACHE_HOST
+            it.get("hb_cache_path_generic") == CACHE_PATH
+            it.get("hb_cache_host_generic") == CACHE_HOST
         }
 
         and: "Debug should contain http call"
@@ -648,8 +647,8 @@ class CacheSpec extends BaseSpec {
             it.get("hb_cache_id_generic")
             it.get("hb_cache_path") == INTERNAL_CACHE_PATH
             it.get("hb_cache_host") == networkServiceContainer.hostAndPort.toString()
-            it.get("hb_cache_path_generic".substring(0, TARGETING_PARAM_NAME_MAX_LENGTH)) == INTERNAL_CACHE_PATH
-            it.get("hb_cache_host_generic".substring(0, TARGETING_PARAM_NAME_MAX_LENGTH)) == networkServiceContainer.hostAndPort.toString()
+            it.get("hb_cache_path_generic") == INTERNAL_CACHE_PATH
+            it.get("hb_cache_host_generic") == networkServiceContainer.hostAndPort.toString()
         }
 
         and: "Debug should contain http call"