tests: enhanced integration tests to cover ? placeholders (#32)

also removed some unreachable code which wrongly lowered coverage

internal/isql/connection_test.go

@@ -263,11 +263,11 @@ func testInsert(t *testing.T, conn *sql.DB) {
 	require.NoError(t, err)
 	_, err = conn.Exec("CREATE TABLE test(a int)")
 	require.NoError(t, err)
-	insertRes, err := conn.Exec("INSERT INTO test (a) VALUES (1)")
+	insertRes, err := conn.Exec("INSERT INTO test (a) VALUES (?)", 1)
 	require.NoError(t, err)
 	_, err = insertRes.RowsAffected()
 	require.Error(t, err) // not supported yet, see todo in statement.go/exec
-	selectRes, err := conn.Query("SELECT * FROM test WHERE a = 1 LIMIT 1")
+	selectRes, err := conn.Query("SELECT * FROM test WHERE a = ? LIMIT 1", 1)
 	require.NoError(t, err)
 	defer fi.NoErrorF(selectRes.Close, t)
 	require.True(t, selectRes.Next())

internal/isql/statement.go

@@ -25,6 +25,10 @@ func (s *Stmt) Close() error {
 
 // NumInput returns number of inputs
 func (s *Stmt) NumInput() int {
+	// -1 means the driver doesn't know how to count the number of
+	// placeholders, so (database/sql) won't sanity check input
+	// See https://cs.opensource.google/go/go/+/refs/tags/go1.23.4:src/database/sql/convert.go;l=109
+	// We could implement counting placeholders in the future.
 	return -1
 }
 
@@ -43,17 +47,15 @@ func (s *Stmt) CheckNamedValue(val *driver.NamedValue) error {
 // Exec executes a query that doesn't return rows
 func (s *Stmt) Exec(args []driver.Value) (driver.Result, error) {
 	// This implementation is never used in recent versions of Go - ExecContext is used instead
-	// even when the user calls sql.Stmt.Exec(). We could implement this required interface method
-	// with panic("not implemented") but we keep a full implementation just in case.
-	nargs := toNamedValues(args)
-	return s.ExecContext(context.Background(), nargs)
+	// even when the user calls sql.Stmt.Exec(). Following the example in database/sql/fakedb_test.go
+	// we can implement this as:
+	panic("ExecContext was not called.")
 }
 
 // Query executes a query that may return rows
 func (s *Stmt) Query(args []driver.Value) (driver.Rows, error) {
 	// Comment in Exec() above applies here as well.
-	nargs := toNamedValues(args)
-	return s.QueryContext(context.Background(), nargs)
+	panic("QueryContext was not called.")
 }
 
 // QueryContext executes a query that may return rows
@@ -76,15 +78,6 @@ func (s *Stmt) ExecContext(ctx context.Context, args []driver.NamedValue) (drive
 	return exec(ctx, session, stmt)
 }
 
-func toNamedValues(args []driver.Value) []driver.NamedValue {
-	// note that database/sql ensures Value never wraps a NamedValue so we don't need to check
-	nargs := make([]driver.NamedValue, len(args))
-	for i, arg := range args {
-		nargs[i] = driver.NamedValue{Ordinal: i, Value: arg}
-	}
-	return nargs
-}
-
 func template(query string) string {
 	ordinal := 1
 	for {