Default tags on tag-less webhook operations to avoid NPE

Webhook operations normally omit `tags`, but createOperation requires
one (Objects.requireNonNull), so a realistic tag-less webhook crashed
with a NullPointerException in the default by-url grouping mode - and
was silently skipped in tag-grouping mode. The prior test masked this
by giving the webhook explicit tags.

mergeWebhooksIntoPaths now defaults each webhook operation's tags to the
webhook name when absent/empty, and skips blank keys (guards the
pathUrl.split()[1] grouping). The testWebhooks fixture is updated to the
realistic tag-less shape to cover this.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: joseegarcia

multiapi-engine/src/main/java/com/sngular/api/generator/plugin/openapi/utils/OpenApiUtil.java

@@ -110,14 +110,35 @@ public static void mergeWebhooksIntoPaths(final JsonNode openApi) {
           ? (ObjectNode) root.get(PATHS)
           : root.putObject(PATHS);
       webhooks.fields().forEachRemaining(webhook -> {
-        final String pathKey = webhook.getKey().startsWith("/") ? webhook.getKey() : "/" + webhook.getKey();
-        if (!paths.has(pathKey)) {
+        final String webhookName = webhook.getKey();
+        final String pathKey = webhookName.startsWith("/") ? webhookName : "/" + webhookName;
+        // A leading-slash-only key would break the by-url grouping (pathUrl.split("/")[1]).
+        if (StringUtils.isNotBlank(StringUtils.strip(webhookName, "/")) && !paths.has(pathKey)) {
+          defaultOperationTags(webhook.getValue(), StringUtils.strip(webhookName, "/"));
           paths.set(pathKey, webhook.getValue());
         }
       });
     }
   }
 
+  /**
+   * Ensures every operation of a webhook-derived Path Item carries a {@code tags} entry. Webhook
+   * operations normally omit {@code tags}, but the path pipeline requires one; a missing/empty
+   * {@code tags} is defaulted to the webhook name so generation works in both grouping modes.
+   */
+  private static void defaultOperationTags(final JsonNode pathItem, final String defaultTag) {
+    if (pathItem instanceof ObjectNode) {
+      pathItem.fields().forEachRemaining(field -> {
+        if (REST_VERB_SET.contains(field.getKey()) && field.getValue() instanceof ObjectNode) {
+          final ObjectNode operation = (ObjectNode) field.getValue();
+          if (!ApiTool.hasNode(operation, "tags") || !operation.get("tags").isArray() || operation.get("tags").isEmpty()) {
+            operation.putArray("tags").add(defaultTag);
+          }
+        }
+      });
+    }
+  }
+
   public static Map<String, JsonNode> processPaths(final JsonNode openApi, final Map<String, JsonNode> schemaMap, SpecFile specFile) {
     final var basicJsonNodeMap = new HashMap<>(schemaMap);
 

multiapi-engine/src/test/resources/openapigenerator/testWebhooks/api-test.yml

@@ -18,8 +18,8 @@ webhooks:
     post:
       summary: New pet notification
       operationId: newPetWebhook
-      tags:
-        - webhook
+      # No `tags`: webhook operations normally omit them. The merge defaults the tag
+      # to the webhook name so generation works in the default (by-url) grouping mode.
       requestBody:
         content:
           application/json:

multiapi-engine/src/test/resources/openapigenerator/testWebhooks/assets/NewPetApi.java

@@ -29,7 +29,7 @@ public interface NewPetApi {
   @Operation(
     operationId = "newPetWebhook",
     summary = "New pet notification",
-    tags = {"webhook"},
+    tags = {"newPet"},
     responses = {
       @ApiResponse(responseCode = "200", description = "Notification acknowledged")
     }