Wrapping string in try/catch and adding test

Author: jonathan-buttner

x-pack/plugin/inference/src/main/java/org/elasticsearch/xpack/inference/services/custom/CustomResponseHandler.java

@@ -8,6 +8,7 @@
 package org.elasticsearch.xpack.inference.services.custom;
 
 import org.elasticsearch.ElasticsearchStatusException;
+import org.elasticsearch.common.Strings;
 import org.elasticsearch.inference.InferenceServiceResults;
 import org.elasticsearch.rest.RestStatus;
 import org.elasticsearch.xpack.inference.external.http.HttpResult;
@@ -24,9 +25,14 @@
  * Defines how to handle various response types returned from the custom integration.
  */
 public class CustomResponseHandler extends BaseResponseHandler {
-    private static final Function<HttpResult, ErrorResponse> ERROR_PARSER = (httpResult) -> new ErrorResponse(
-        new String(httpResult.body(), StandardCharsets.UTF_8)
-    );
+    // default for testing
+    static final Function<HttpResult, ErrorResponse> ERROR_PARSER = (httpResult) -> {
+        try {
+            return new ErrorResponse(new String(httpResult.body(), StandardCharsets.UTF_8));
+        } catch (Exception e) {
+            return new ErrorResponse(Strings.format("Failed to parse error response body: %s", e.getMessage()));
+        }
+    };
 
     public CustomResponseHandler(String requestType, ResponseParser parseFunction) {
         super(requestType, parseFunction, ERROR_PARSER);

x-pack/plugin/inference/src/test/java/org/elasticsearch/xpack/inference/services/custom/CustomResponseHandlerTests.java

@@ -0,0 +1,62 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License
+ * 2.0; you may not use this file except in compliance with the Elastic License
+ * 2.0.
+ */
+
+package org.elasticsearch.xpack.inference.services.custom;
+
+import org.apache.http.HttpResponse;
+import org.apache.http.StatusLine;
+import org.elasticsearch.common.Strings;
+import org.elasticsearch.common.xcontent.XContentHelper;
+import org.elasticsearch.test.ESTestCase;
+import org.elasticsearch.xpack.inference.external.http.HttpResult;
+import org.elasticsearch.xpack.inference.external.http.retry.ErrorResponse;
+
+import java.io.IOException;
+import java.nio.charset.StandardCharsets;
+
+import static org.elasticsearch.xpack.inference.services.custom.CustomResponseHandler.ERROR_PARSER;
+import static org.hamcrest.Matchers.is;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+public class CustomResponseHandlerTests extends ESTestCase {
+
+    public void testErrorBodyParser() throws IOException {
+        var expected = XContentHelper.stripWhitespace(Strings.format("""
+                {
+                    "error": {
+                        "message": "%s",
+                        "type": "content_too_large",
+                        "param": null,
+                        "code": null
+                    }
+                }
+            """, "message"));
+
+        assertThat(ERROR_PARSER.apply(createResult(400, "message")), is(new ErrorResponse(expected)));
+    }
+
+    private static HttpResult createResult(int statusCode, String message) throws IOException {
+        var statusLine = mock(StatusLine.class);
+        when(statusLine.getStatusCode()).thenReturn(statusCode);
+        var httpResponse = mock(HttpResponse.class);
+        when(httpResponse.getStatusLine()).thenReturn(statusLine);
+
+        String responseJson = XContentHelper.stripWhitespace(Strings.format("""
+                {
+                    "error": {
+                        "message": "%s",
+                        "type": "content_too_large",
+                        "param": null,
+                        "code": null
+                    }
+                }
+            """, message));
+
+        return new HttpResult(httpResponse, responseJson.getBytes(StandardCharsets.UTF_8));
+    }
+}