Add missing files in exception message

include/storage/io_config.hpp

@@ -24,6 +24,7 @@ struct IOConfig
     }
 
     bool IsValid() const;
+    std::vector<std::string> GetMissingFiles() const;
     boost::filesystem::path GetPath(const std::string &fileName) const
     {
         if (!IsConfigured(fileName, required_input_files) &&

src/osrm/osrm.cpp

@@ -10,6 +10,8 @@
 #include "engine/engine_config.hpp"
 #include "engine/status.hpp"
 
+#include <boost/algorithm/string/join.hpp>
+
 #include <memory>
 
 namespace osrm
@@ -25,8 +27,11 @@ OSRM::OSRM(engine::EngineConfig &config)
     // First, check that necessary core data is available
     if (!config.use_shared_memory && !config.storage_config.IsValid())
     {
+        const auto &missingFiles = config.storage_config.GetMissingFiles();
         throw util::exception("Required files are missing, cannot continue. Have all the "
-                              "pre-processing steps been run?");
+                              "pre-processing steps been run? "
+                              "Missing files: " +
+                              boost::algorithm::join(missingFiles, ", "));
     }
 
     // Now, check that the algorithm requested can be used with the data

src/storage/io_config.cpp

@@ -26,5 +26,18 @@ bool IOConfig::IsValid() const
     }
     return success;
 }
+
+std::vector<std::string> IOConfig::GetMissingFiles() const
+{
+    std::vector<std::string> missingFiles;
+    for (auto &fileName : required_input_files)
+    {
+        if (!boost::filesystem::is_regular_file({base_path.string() + fileName.string()}))
+        {
+            missingFiles.push_back(base_path.string() + fileName.string());
+        }
+    }
+    return missingFiles;
+}
 } // namespace storage
 } // namespace osrm