chore(search): improve parser error reporting

Also, warn explicitly about lack of scoring support for vector search.

Signed-off-by: Roman Gershman <[email protected]>

Author: romange

src/core/search/parser.y

@@ -174,5 +174,5 @@ tag_list:
 void
 dfly::search::Parser::error(const location_type& l, const string& m)
 {
-  cerr << l << ": " << m << '\n';
+  driver->Error(l, m);
 }

src/core/search/query_driver.cc

@@ -18,6 +18,10 @@ void QueryDriver::ResetScanner() {
   scanner_->SetParams(params_);
 }
 
+void QueryDriver::Error(const Parser::location_type& loc, std::string_view msg) {
+  LOG(ERROR) << "Parse error " << loc << ": " << msg;
+}
+
 }  // namespace search
 
 }  // namespace dfly

src/core/search/query_driver.h

@@ -52,6 +52,8 @@ class QueryDriver {
     return scanner_.get();
   }
 
+  void Error(const Parser::location_type& loc, std::string_view msg);
+
  public:
   Parser::location_type location;
 

src/core/search/search.cc

@@ -488,6 +488,9 @@ void FieldIndices::CreateIndices(PMR_NS::memory_resource* mr) {
           vector_index = make_unique<FlatVectorIndex>(vparams, mr);
 
         indices_[field_ident] = std::move(vector_index);
+        LOG_FIRST_N(WARNING, 1)
+            << "Created vector index '" << field_ident
+            << "', but the computed score field '__vector_score' is not supported yet";
         break;
       }
     }