Enforcing "NOT" and "-" queries consistency in UserInputAst

query-grammar/src/query_grammar.rs

@@ -374,6 +374,25 @@ pub fn parse_to_ast<'a>() -> impl Parser<&'a str, Output = UserInputAst> {
     spaces()
         .with(optional(ast()).skip(eof()))
         .map(|opt_ast| opt_ast.unwrap_or_else(UserInputAst::empty_query))
+        .map(|ast| rewrite_ast(ast))
+}
+
+/// Removes unnecessary children clauses in AST
+///
+/// Motivated by [issue #1433](https://github.com/quickwit-oss/tantivy/issues/1433)
+fn rewrite_ast(input: UserInputAst) -> UserInputAst {
+    if let UserInputAst::Clause(terms) = input {
+        UserInputAst::Clause(terms.into_iter().map(rewrite_ast_clause).collect())
+    } else {
+        input
+    }
+}
+
+fn rewrite_ast_clause(input: (Option<Occur>, UserInputAst)) -> (Option<Occur>, UserInputAst) {
+    match input {
+        (None, UserInputAst::Clause(mut clauses)) if clauses.len() == 1 => clauses.remove(0),
+        other => other,
+    }
 }
 
 #[cfg(test)]
@@ -749,4 +768,10 @@ mod test {
         test_parse_query_to_ast_helper("foo:\"a b\"~300", "\"foo\":\"a b\"~300");
         test_parse_query_to_ast_helper("\"a b\"~300^2", "(\"a b\"~300)^2");
     }
+
+    #[test]
+    fn test_not_queries_are_consistent() {
+        test_parse_query_to_ast_helper("tata -toto", "(*\"tata\" -\"toto\")");
+        test_parse_query_to_ast_helper("tata NOT toto", "(*\"tata\" -\"toto\")");
+    }
 }