[C++][Pistache] Fixes for struct model (#12006)

* [C++][Pistache] fix Wconversion warning

* [C++][Pistache] fix struct model compilation with std::optional

* [C++][Pistache] Add validation to struct model

modules/openapi-generator/src/main/resources/cpp-pistache-server/helpers-source.mustache

@@ -37,15 +37,21 @@ namespace
 bool validateRfc3339_date(const std::string& str) {
     std::smatch match;
     const bool found = std::regex_search(str, match, regexRfc3339_date);
-    return found && validateDateValues(std::stoi(match[1]), std::stoi(match[2]), std::stoi(match[3]));
+    return found && validateDateValues(static_cast<uint16_t>(std::stoi(match[1])),
+                                       static_cast<uint16_t>(std::stoi(match[2])),
+                                       static_cast<uint16_t>(std::stoi(match[3])));
 }
 
 bool validateRfc3339_date_time(const std::string& str) {
     std::smatch match;
     const bool found = std::regex_search(str, match, regexRfc3339_date_time);
     return found
-        && validateDateValues(std::stoi(match[1]), std::stoi(match[2]), std::stoi(match[3]))
-        && validateTimeValues(std::stoi(match[4]), std::stoi(match[5]), std::stoi(match[6]));
+        && validateDateValues(static_cast<uint16_t>(std::stoi(match[1])),
+                              static_cast<uint16_t>(std::stoi(match[2])),
+                              static_cast<uint16_t>(std::stoi(match[3])))
+        && validateTimeValues(static_cast<uint16_t>(std::stoi(match[4])),
+                              static_cast<uint16_t>(std::stoi(match[5])),
+                              static_cast<uint16_t>(std::stoi(match[6])));
 }
 
 std::string toStringValue(const std::string &value){

modules/openapi-generator/src/main/resources/cpp-pistache-server/model-struct-header.mustache

@@ -26,6 +26,23 @@ struct {{classname}}
     bool operator==(const {{classname}}& other) const;
     bool operator!=(const {{classname}}& other) const;
 
+    /// <summary>
+    /// Validate the current data in the model. Throws a ValidationException on failure.
+    /// </summary>
+    void validate() const;
+
+    /// <summary>
+    /// Validate the current data in the model. Returns false on error and writes an error
+    /// message into the given stringstream.
+    /// </summary>
+    bool validate(std::stringstream& msg) const;
+
+    /// <summary>
+    /// Helper overload for validate. Used when one model stores another model and calls it's validate.
+    /// Not meant to be called outside that case.
+    /// </summary>
+    bool validate(std::stringstream& msg, const std::string& pathPrefix) const;
+
     nlohmann::json to_json() const;
     static {{classname}} from_json(const nlohmann::json& j);
 };

modules/openapi-generator/src/main/resources/cpp-pistache-server/model-struct-source.mustache

@@ -2,6 +2,7 @@
 {{#models}}{{#model}}
 
 #include "{{classname}}.h"
+#include "{{prefix}}Helpers.h"
 
 namespace {{modelNamespace}}
 {
@@ -20,6 +21,56 @@ nlohmann::json {{classname}}::to_json() const
     return o;
 }
 
+void {{classname}}::validate() const
+{
+    std::stringstream msg;
+    if (!validate(msg))
+    {
+        throw {{helpersNamespace}}::ValidationException(msg.str());
+    }
+}
+
+bool {{classname}}::validate(std::stringstream& msg) const
+{
+    return validate(msg, "");
+}
+
+bool {{classname}}::validate(std::stringstream& msg, const std::string& pathPrefix) const
+{
+    bool success = true;
+    const std::string _pathPrefix = pathPrefix.empty() ? "{{classname}}" : pathPrefix;
+
+    {{#isEnum}}{{! Special case for enum types }}
+    if (m_value == {{classname}}::e{{classname}}::INVALID_VALUE_OPENAPI_GENERATED)
+    {
+        success = false;
+        msg << _pathPrefix << ": has no value;";
+    }
+    {{/isEnum}}
+    {{^isEnum}}
+    {{#vars}}
+    {{#isArray}} {{! Always generate validation body for array types }}
+    {{^required}}if ({{name}}.has_value()){{/required}}
+    {{#required}}/* {{name}} */ {{/required}}{
+        const {{{dataType}}}& value = {{name}}{{^required}}.value(){{/required}};
+        const std::string currentValuePath = _pathPrefix + ".{{nameInCamelCase}}";
+        {{> model-validation-body }}
+    }
+    {{/isArray}}{{^isArray}}{{#hasValidation}} {{! Only generate validation if necessary }}
+    {{^required}}if ({{name}}.has_value()){{/required}}
+    {{#required}}/* {{name}} */ {{/required}}{
+        const {{{dataType}}}& value = {{name}}{{^required}}.value(){{/required}};
+        const std::string currentValuePath = _pathPrefix + ".{{nameInCamelCase}}";
+        {{> model-validation-body }}
+    }
+    {{/hasValidation}}{{/isArray}}{{/vars}}{{/isEnum}}{{#vendorExtensions.x-is-string-enum-container}}{{#anyOf}}{{#-first}}
+    if (!m_value.validate(msg))
+    {
+        success = false;
+    }{{/-first}}{{/anyOf}}{{/vendorExtensions.x-is-string-enum-container}}
+    return success;
+}
+
 bool {{classname}}::operator==(const {{classname}}& other) const
 {
     return {{#vars}}{{name}} == other.{{name}}{{^-last}} && {{/-last}}{{/vars}};
@@ -33,8 +84,8 @@ bool {{classname}}::operator!=(const {{classname}}& other) const
 void to_json(nlohmann::json& j, const {{classname}}& o)
 {
     {{#vars}}
-    {{^required}}if (!o.{{name}}.isEmpty()){{/required}}
-        j["{{baseName}}"] = o.{{name}}{{^required}}.get(){{/required}};
+    {{^required}}if (o.{{name}}.has_value()){{/required}}
+        j["{{baseName}}"] = o.{{name}}{{^required}}.value(){{/required}};
     {{/vars}}
 }
 

samples/server/petstore/cpp-pistache/model/Helpers.cpp

@@ -47,15 +47,21 @@ namespace
 bool validateRfc3339_date(const std::string& str) {
     std::smatch match;
     const bool found = std::regex_search(str, match, regexRfc3339_date);
-    return found && validateDateValues(std::stoi(match[1]), std::stoi(match[2]), std::stoi(match[3]));
+    return found && validateDateValues(static_cast<uint16_t>(std::stoi(match[1])),
+                                       static_cast<uint16_t>(std::stoi(match[2])),
+                                       static_cast<uint16_t>(std::stoi(match[3])));
 }
 
 bool validateRfc3339_date_time(const std::string& str) {
     std::smatch match;
     const bool found = std::regex_search(str, match, regexRfc3339_date_time);
     return found
-        && validateDateValues(std::stoi(match[1]), std::stoi(match[2]), std::stoi(match[3]))
-        && validateTimeValues(std::stoi(match[4]), std::stoi(match[5]), std::stoi(match[6]));
+        && validateDateValues(static_cast<uint16_t>(std::stoi(match[1])),
+                              static_cast<uint16_t>(std::stoi(match[2])),
+                              static_cast<uint16_t>(std::stoi(match[3])))
+        && validateTimeValues(static_cast<uint16_t>(std::stoi(match[4])),
+                              static_cast<uint16_t>(std::stoi(match[5])),
+                              static_cast<uint16_t>(std::stoi(match[6])));
 }
 
 std::string toStringValue(const std::string &value){