Auto-quote bare string parameters for DDS content filter expressions

Fast DDS requires content filter expression parameters to be valid
DDS SQL literals. Bare strings like "hello" fail to parse in
DDSFilterParameter::set_value() because the DDSSQLFilter grammar
expects string literals to be single-quoted ('hello').

This causes content filter parameter substitution (%0, %1, ...) to
silently fail for string-typed fields when users pass unquoted values,
which is the natural thing to do from a CLI or application perspective.

Add ensure_dds_literal() that detects bare strings (not already a
number, boolean, or quoted string) and wraps them in single quotes
before passing to Fast DDS. Applied at both content filter creation
and dynamic filter update call sites.

References: eProsima/Fast-DDS#4199

Author: PavelGuzenfeld

rmw_fastrtps_shared_cpp/include/rmw_fastrtps_shared_cpp/utils.hpp

@@ -15,8 +15,10 @@
 #ifndef RMW_FASTRTPS_SHARED_CPP__UTILS_HPP_
 #define RMW_FASTRTPS_SHARED_CPP__UTILS_HPP_
 
+#include <cctype>
 #include <mutex>
 #include <string>
+#include <vector>
 
 #include "fastdds/dds/topic/TopicDescription.hpp"
 #include "fastdds/dds/topic/TypeSupport.hpp"
@@ -33,6 +35,59 @@
 namespace rmw_fastrtps_shared_cpp
 {
 
+/// Ensure a content filter parameter is a valid DDS SQL literal.
+///
+/// Fast DDS requires content filter parameters to be parseable as DDS SQL
+/// literals.  Bare strings like "hello" must be wrapped in single quotes to
+/// become valid string literals ('hello'), otherwise
+/// DDSFilterParameter::set_value() fails with a parse error.
+/// See https://github.com/eProsima/Fast-DDS/issues/4199
+inline std::string
+ensure_dds_literal(const std::string & value)
+{
+  if (value.empty()) {
+    return "'" + value + "'";
+  }
+
+  // Already a quoted string
+  if ((value.front() == '\'' || value.front() == '`') && value.size() >= 2 &&
+    value.back() == value.front())
+  {
+    return value;
+  }
+
+  // Boolean literals
+  if (value == "TRUE" || value == "FALSE") {
+    return value;
+  }
+
+  // Numeric: optional leading sign, then digit or dot (covers int, float, hex)
+  const char * p = value.c_str();
+  if (*p == '+' || *p == '-') {
+    ++p;
+  }
+  if (*p == '0' && (*(p + 1) == 'x' || *(p + 1) == 'X')) {
+    return value;  // hex
+  }
+  if (std::isdigit(static_cast<unsigned char>(*p)) || *p == '.') {
+    return value;  // numeric
+  }
+
+  // Not a recognized literal — wrap in single quotes
+  return "'" + value + "'";
+}
+
+/// Convert rmw content filter parameters, auto-quoting bare strings for Fast DDS.
+inline std::vector<std::string>
+prepare_content_filter_parameters(const rmw_subscription_content_filter_options_t * options)
+{
+  std::vector<std::string> expression_parameters;
+  for (size_t i = 0; i < options->expression_parameters.size; ++i) {
+    expression_parameters.push_back(ensure_dds_literal(options->expression_parameters.data[i]));
+  }
+  return expression_parameters;
+}
+
 /**
 * Convert a Fast DDS return code into the corresponding rmw_ret_t
 * \param[in] code The Fast DDS return code to be translated

rmw_fastrtps_shared_cpp/src/rmw_subscription.cpp

@@ -120,10 +120,8 @@ __rmw_subscription_set_content_filter(
       "current subscriber has no content filter topic");
     return RMW_RET_ERROR;
   } else if (filtered_topic && !filter_expression_empty) {
-    std::vector<std::string> expression_parameters;
-    for (size_t i = 0; i < options->expression_parameters.size; ++i) {
-      expression_parameters.push_back(options->expression_parameters.data[i]);
-    }
+    std::vector<std::string> expression_parameters =
+      rmw_fastrtps_shared_cpp::prepare_content_filter_parameters(options);
 
     eprosima::fastdds::dds::ReturnCode_t ret =
       filtered_topic->set_filter_expression(options->filter_expression, expression_parameters);

rmw_fastrtps_shared_cpp/src/utils.cpp

@@ -102,10 +102,7 @@ create_content_filtered_topic(
   const rmw_subscription_content_filter_options_t * options,
   eprosima::fastdds::dds::ContentFilteredTopic ** content_filtered_topic)
 {
-  std::vector<std::string> expression_parameters;
-  for (size_t i = 0; i < options->expression_parameters.size; ++i) {
-    expression_parameters.push_back(options->expression_parameters.data[i]);
-  }
+  std::vector<std::string> expression_parameters = prepare_content_filter_parameters(options);
 
   auto topic = dynamic_cast<eprosima::fastdds::dds::Topic *>(topic_desc);
   static std::atomic<uint32_t> cft_counter{0};