From ab79599a5ef01ea4015731e01c0348b6b7de0024 Mon Sep 17 00:00:00 2001
From: Timothy Flynn <trflynn89@pm.me>
Date: Tue, 1 Jun 2021 08:34:51 -0400
Subject: LibSQL: Return an error for empty common table expression lists

SQL::CommonTableExpressionList is required to be non-empty. Return an
error if zero common table expressions were parsed.

Fixes #7627
---
 Tests/LibSQL/TestSqlStatementParser.cpp |  2 ++
 Userland/Libraries/LibSQL/Parser.cpp    | 10 +++++++++-
 Userland/Libraries/LibSQL/Parser.h      |  2 +-
 3 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/Tests/LibSQL/TestSqlStatementParser.cpp b/Tests/LibSQL/TestSqlStatementParser.cpp
index 0126a85e4e..64fbe3fb3e 100644
--- a/Tests/LibSQL/TestSqlStatementParser.cpp
+++ b/Tests/LibSQL/TestSqlStatementParser.cpp
@@ -682,6 +682,8 @@ TEST_CASE(select)
 
 TEST_CASE(common_table_expression)
 {
+    EXPECT(parse("WITH").is_error());
+    EXPECT(parse("WITH;").is_error());
     EXPECT(parse("WITH DELETE FROM table;").is_error());
     EXPECT(parse("WITH table DELETE FROM table;").is_error());
     EXPECT(parse("WITH table AS DELETE FROM table;").is_error());
diff --git a/Userland/Libraries/LibSQL/Parser.cpp b/Userland/Libraries/LibSQL/Parser.cpp
index 3e71e1e83f..b12ed59717 100644
--- a/Userland/Libraries/LibSQL/Parser.cpp
+++ b/Userland/Libraries/LibSQL/Parser.cpp
@@ -23,6 +23,9 @@ NonnullRefPtr<Statement> Parser::next_statement()
 
     if (match(TokenType::With)) {
         auto common_table_expression_list = parse_common_table_expression_list();
+        if (!common_table_expression_list)
+            return create_ast_node<ErrorStatement>();
+
         return terminate_statement(parse_statement_with_expression_list(move(common_table_expression_list)));
     }
 
@@ -331,7 +334,7 @@ NonnullRefPtr<Select> Parser::parse_select_statement(RefPtr<CommonTableExpressio
     return create_ast_node<Select>(move(common_table_expression_list), select_all, move(result_column_list), move(table_or_subquery_list), move(where_clause), move(group_by_clause), move(ordering_term_list), move(limit_clause));
 }
 
-NonnullRefPtr<CommonTableExpressionList> Parser::parse_common_table_expression_list()
+RefPtr<CommonTableExpressionList> Parser::parse_common_table_expression_list()
 {
     consume(TokenType::With);
     bool recursive = consume_if(TokenType::Recursive);
@@ -339,6 +342,11 @@ NonnullRefPtr<CommonTableExpressionList> Parser::parse_common_table_expression_l
     NonnullRefPtrVector<CommonTableExpression> common_table_expression;
     parse_comma_separated_list(false, [&]() { common_table_expression.append(parse_common_table_expression()); });
 
+    if (common_table_expression.is_empty()) {
+        expected("Common table expression list");
+        return {};
+    }
+
     return create_ast_node<CommonTableExpressionList>(recursive, move(common_table_expression));
 }
 
diff --git a/Userland/Libraries/LibSQL/Parser.h b/Userland/Libraries/LibSQL/Parser.h
index 4d1c888e37..74595a3b7e 100644
--- a/Userland/Libraries/LibSQL/Parser.h
+++ b/Userland/Libraries/LibSQL/Parser.h
@@ -59,7 +59,7 @@ private:
     NonnullRefPtr<Update> parse_update_statement(RefPtr<CommonTableExpressionList>);
     NonnullRefPtr<Delete> parse_delete_statement(RefPtr<CommonTableExpressionList>);
     NonnullRefPtr<Select> parse_select_statement(RefPtr<CommonTableExpressionList>);
-    NonnullRefPtr<CommonTableExpressionList> parse_common_table_expression_list();
+    RefPtr<CommonTableExpressionList> parse_common_table_expression_list();
 
     NonnullRefPtr<Expression> parse_primary_expression();
     NonnullRefPtr<Expression> parse_secondary_expression(NonnullRefPtr<Expression> primary);
-- 
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