local_reply_config : support content-type in SubstitutionFormatString

api/envoy/config/core/v3/substitution_format_string.proto

@@ -65,4 +65,14 @@ message SubstitutionFormatString {
   //   empty string, so that empty values are omitted entirely.
   // * for ``json_format`` the keys with null values are omitted in the output structure.
   bool omit_empty_values = 3;
+
+  // Specify a content_type for text_format. This will be ignored for json_format.
+  // Currently supported content-type value includes ``text/html; charset=UTF-8`` and ``text/plain``
+  // with default value being ``text/plain``.
+  //
+  // .. code-block::
+  //
+  //   content_type: "text/html; charset=UTF-8"
+  //
+  string content_type = 4;
 }

docs/root/configuration/http/http_conn_man/local_reply.rst

@@ -49,6 +49,8 @@ The response body content type can be customized. If not specified, the content
 
 Local reply format can be specified as :ref:`SubstitutionFormatString <envoy_v3_api_msg_config.core.v3.SubstitutionFormatString>`. It supports :ref:`text_format <envoy_v3_api_field_config.core.v3.SubstitutionFormatString.text_format>` and :ref:`json_format <envoy_v3_api_field_config.core.v3.SubstitutionFormatString.json_format>`.
 
+If local reply format is :ref:`text_format <envoy_v3_api_field_config.core.v3.SubstitutionFormatString.text_format>` then content-type can be modified further via :ref:`content_type <envoy_v3_api_field_config.core.v3.SubstitutionFormatString.content_type>`. Supported content-type values include `text/html; charset=UTF-8` and `text/plain` with default value being `text/plain`.
+
 Example of a LocalReplyConfig with `body_format` field.
 
 .. code-block::
@@ -63,7 +65,8 @@ Example of a LocalReplyConfig with `body_format` field.
             runtime_key: key_b
     status_code: 401
     body_format_override:
-      text_format: "%LOCAL_REPLY_BODY% %REQ(:path)%"
+      text_format: "<h1>%LOCAL_REPLY_BODY% %REQ(:path)%</h1>"
+      content_type: "text/html; charset=UTF-8"
   - filter:
       status_code_filter:
         comparison:

docs/root/version_history/current.rst

@@ -84,6 +84,7 @@ New Features
 * load balancer: added a :ref:`configuration<envoy_v3_api_msg_config.cluster.v3.Cluster.LeastRequestLbConfig>` option to specify the active request bias used by the least request load balancer.
 * load balancer: added an :ref:`option <envoy_v3_api_field_config.cluster.v3.Cluster.LbSubsetConfig.LbSubsetSelector.single_host_per_subset>` to optimize subset load balancing when there is only one host per subset.
 * load balancer: added support for bounded load per host for consistent hash load balancers via :ref:`hash_balance_factor <envoy_api_field_Cluster.CommonLbConfig.consistent_hashing_lb_config>`.
+* local_reply config: added :ref:`content_type<envoy_v3_api_field_config.core.v3.SubstitutionFormatString.content_type>` option to set content-type for textformat.
 * lua: added Lua APIs to access :ref:`SSL connection info <config_http_filters_lua_ssl_socket_info>` object.
 * lua: added Lua API for :ref:`base64 escaping a string <config_http_filters_lua_stream_handle_api_base64_escape>`.
 * lua: added new :ref:`source_code <envoy_v3_api_field_extensions.filters.http.lua.v3.LuaPerRoute.source_code>` field to support the dispatching of inline Lua code in per route configuration of Lua filter.

source/common/formatter/substitution_format_string.cc

@@ -1,6 +1,7 @@
 #include "common/formatter/substitution_format_string.h"
 
 #include "common/formatter/substitution_formatter.h"
+#include "common/http/headers.h"
 
 namespace Envoy {
 namespace Formatter {
@@ -25,5 +26,13 @@ FormatterPtr SubstitutionFormatStringUtils::fromProtoConfig(
   return nullptr;
 }
 
+absl::string_view SubstitutionFormatStringUtils::getContentType(
+    const envoy::config::core::v3::SubstitutionFormatString& config) {
+  if (config.content_type() == Http::Headers::get().ContentTypeValues.Html) {
+    return Http::Headers::get().ContentTypeValues.Html;
+  }
+  return Http::Headers::get().ContentTypeValues.Text;
+}
+
 } // namespace Formatter
 } // namespace Envoy

source/common/formatter/substitution_format_string.h

@@ -26,6 +26,12 @@ class SubstitutionFormatStringUtils {
    */
   static FormatterPtr createJsonFormatter(const ProtobufWkt::Struct& struct_format,
                                           bool preserve_types, bool omit_empty_values);
+
+  /**
+   * Returns content-type from config SubstitutionFormatString
+   */
+  static absl::string_view
+  getContentType(const envoy::config::core::v3::SubstitutionFormatString& config);
 };
 
 } // namespace Formatter

source/common/local_reply/local_reply.cc

@@ -26,7 +26,7 @@ class BodyFormatter {
             config.format_case() ==
                     envoy::config::core::v3::SubstitutionFormatString::FormatCase::kJsonFormat
                 ? Http::Headers::get().ContentTypeValues.Json
-                : Http::Headers::get().ContentTypeValues.Text) {}
+                : Formatter::SubstitutionFormatStringUtils::getContentType(config)) {}
 
   void format(const Http::RequestHeaderMap& request_headers,
               const Http::ResponseHeaderMap& response_headers,

test/common/formatter/substitution_format_string_test.cc

@@ -94,5 +94,15 @@ TEST_F(SubstitutionFormatStringUtilsTest, TestInvalidConfigs) {
   }
 }
 
+TEST_F(SubstitutionFormatStringUtilsTest, TestFromProtoConfigContentType) {
+  const std::string yaml = R"EOF(
+  text_format: "<h1>Sample html</h1>"
+  content_type: "text/html; charset=UTF-8"
+)EOF";
+  TestUtility::loadFromYaml(yaml, config_);
+  const absl::string_view contentType = SubstitutionFormatStringUtils::getContentType(config_);
+  EXPECT_EQ("text/html; charset=UTF-8", contentType);
+}
+
 } // namespace Formatter
 } // namespace Envoy

test/common/local_reply/local_reply_test.cc

@@ -336,5 +336,62 @@ TEST_F(LocalReplyTest, TestHeaderAddition) {
   ASSERT_EQ(out[1], "append-bar3");
 }
 
+TEST_F(LocalReplyTest, TestMapperWithContentType) {
+  // Match with response_code, and rewrite the code and body.
+  const std::string yaml = R"(
+    mappers:
+    - filter:
+        status_code_filter:
+          comparison:
+            op: EQ
+            value:
+              default_value: 400
+              runtime_key: key_b
+      status_code: 401
+      body:
+        inline_string: "401 body text"
+      body_format_override:
+        text_format: "<h1>%LOCAL_REPLY_BODY%</h1>"
+        content_type: "text/html; charset=UTF-8"
+    - filter:
+        status_code_filter:
+          comparison:
+            op: EQ
+            value:
+              default_value: 410
+              runtime_key: key_b
+      status_code: 411
+      body:
+        inline_string: "411 body text"
+    body_format:
+      text_format: "<h1>%LOCAL_REPLY_BODY%</h1> %RESPONSE_CODE% default formatter"
+      content_type: "text/html; charset=UTF-8"
+)";
+  TestUtility::loadFromYaml(yaml, config_);
+  auto local = Factory::create(config_, context_);
+
+  // code=400 matches the first filter; rewrite code and body
+  // has its own formatter.
+  resetData(400);
+  local->rewrite(&request_headers_, response_headers_, stream_info_, code_, body_, content_type_);
+  EXPECT_EQ(code_, static_cast<Http::Code>(401));
+  EXPECT_EQ(stream_info_.response_code_, 401U);
+  EXPECT_EQ(response_headers_.Status()->value().getStringView(), "401");
+  EXPECT_EQ(content_type_, "text/html; charset=UTF-8");
+
+  const std::string expected = R"(<h1>401 body text</h1>)";
+  EXPECT_EQ(body_, expected);
+
+  // code=410 matches the second filter; rewrite code and body
+  // but using default formatter.
+  resetData(410);
+  local->rewrite(&request_headers_, response_headers_, stream_info_, code_, body_, content_type_);
+  EXPECT_EQ(code_, static_cast<Http::Code>(411));
+  EXPECT_EQ(stream_info_.response_code_, 411U);
+  EXPECT_EQ(response_headers_.Status()->value().getStringView(), "411");
+  EXPECT_EQ(body_, "<h1>411 body text</h1> 411 default formatter");
+  EXPECT_EQ(content_type_, "text/html; charset=UTF-8");
+}
+
 } // namespace LocalReply
 } // namespace Envoy