Improved from_string function for SparseVector

Author: ankane

include/pgvector/pqxx.hpp

@@ -149,8 +149,15 @@ template <> struct string_traits<pgvector::SparseVector> {
                     throw conversion_error("Malformed sparsevec literal");
                 }
 
-                indices.push_back(std::stoi(substr.substr(0, ne)) - 1);
-                values.push_back(std::stof(substr.substr(ne + 1)));
+                int index = std::stoi(substr.substr(0, ne));
+                float value = std::stof(substr.substr(ne + 1));
+
+                if (index < 1) {
+                    throw conversion_error("Malformed sparsevec literal");
+                }
+
+                indices.push_back(index - 1);
+                values.push_back(value);
             }
         }
 

test/pqxx_test.cpp

@@ -263,6 +263,20 @@ void test_sparsevec_from_string() {
         assert(std::string_view(e.what()) == "Malformed sparsevec literal");
     }
 
+    try {
+        auto unused = pqxx::from_string<pgvector::SparseVector>("{0:1}/1");
+        assert(false);
+    } catch (const pqxx::conversion_error& e) {
+        assert(std::string_view(e.what()) == "Malformed sparsevec literal");
+    }
+
+    try {
+        auto unused = pqxx::from_string<pgvector::SparseVector>("{-2147483648:1}/1");
+        assert(false);
+    } catch (const pqxx::conversion_error& e) {
+        assert(std::string_view(e.what()) == "Malformed sparsevec literal");
+    }
+
     // TODO change to pqxx::conversion_error
     try {
         auto unused = pqxx::from_string<pgvector::SparseVector>("{a:1}/1");