fix the default value logic

include/config/config_specification.h

@@ -18,7 +18,7 @@ namespace silo::config {
 /// be supported by env vars or config files anyway, although could
 /// still be specified for command line, but that's not implemented
 /// currently.
-class ConfigSpecification : public VerifiedConfigSource {
+class ConfigSpecification {
   public:
    /// The name of the program for which this config is used. This will be printed in the help text
    std::string_view program_name;
@@ -35,6 +35,8 @@ class ConfigSpecification : public VerifiedConfigSource {
    std::optional<ConfigValueSpecification> getValueSpecificationFromAmbiguousKey(
       const AmbiguousConfigKeyPath& key
    ) const;
+
+   VerifiedConfigSource getConfigSourceFromDefaults() const;
 };
 
 }  // namespace silo::config

src/config/config_specification.cpp

@@ -99,4 +99,15 @@ std::string ConfigSpecification::helpText() const {
 
    return help_text.str();
 }
+
+VerifiedConfigSource ConfigSpecification::getConfigSourceFromDefaults() const {
+   VerifiedConfigSource result;
+   for (auto& x : fields) {
+      if (x.default_value) {
+         result.config_values.emplace(x.key, x.default_value.value());
+      }
+   }
+   return result;
+}
+
 }  // namespace silo::config

src/silo/config/preprocessing_config.cpp

@@ -95,7 +95,7 @@ ConfigSpecification PreprocessingConfig::getConfigSpecification() {
 }
 
 PreprocessingConfig::PreprocessingConfig() {
-   overwriteFrom(getConfigSpecification());
+   overwriteFrom(getConfigSpecification().getConfigSourceFromDefaults());
 }
 
 void PreprocessingConfig::validate() const {

src/silo/config/runtime_config.cpp

@@ -74,7 +74,7 @@ ConfigSpecification RuntimeConfig::getConfigSpecification() {
 }
 
 RuntimeConfig::RuntimeConfig() {
-   overwriteFrom(getConfigSpecification());
+   overwriteFrom(getConfigSpecification().getConfigSourceFromDefaults());
 }
 
 bool RuntimeConfig::asksForHelp() const {