From 3f05ea7c6bf84c82085147edad54b47757ca23c3 Mon Sep 17 00:00:00 2001
From: Roland Bock <rbock@eudoxos.de>
Date: Sat, 2 Nov 2024 22:10:26 +0100
Subject: [PATCH] Add dependency check for CTEs in with

CTEs can use other CTEs iff they have been defined to the left.
---
 include/sqlpp11/core/clause/cte.h    | 22 +++++++++-------------
 include/sqlpp11/core/clause/with.h   | 26 ++++++++++++++++++++++++--
 tests/core/serialize/clause/cte.cpp  | 14 ++++++++++++++
 tests/core/serialize/clause/with.cpp |  9 +++++++++
 4 files changed, 56 insertions(+), 15 deletions(-)

diff --git a/include/sqlpp11/core/clause/cte.h b/include/sqlpp11/core/clause/cte.h
index 5d89516a..07bc94fe 100644
--- a/include/sqlpp11/core/clause/cte.h
+++ b/include/sqlpp11/core/clause/cte.h
@@ -40,8 +40,6 @@ namespace sqlpp
   template <typename Flag, typename Lhs, typename Rhs>
   struct cte_union_t
   {
-    using _nodes = detail::type_vector<>;
-    using _required_ctes = detail::type_vector_cat_t<required_ctes_of_t<Lhs>, required_ctes_of_t<Rhs>>;
     using _parameters = detail::type_vector_cat_t<parameters_of<Lhs>, parameters_of<Rhs>>;
 
     cte_union_t(Lhs lhs, Rhs rhs) : _lhs(lhs), _rhs(rhs)
@@ -58,19 +56,11 @@ namespace sqlpp
     Rhs _rhs;
   };
 
+#warning: need to test nodes of union!
   template <typename Flag, typename Lhs, typename Rhs>
-  struct required_ctes_of<cte_union_t<Flag, Lhs, Rhs>>
+  struct nodes_of<cte_union_t<Flag, Lhs, Rhs>>
   {
-    using type = detail::type_vector_cat_t<required_ctes_of_t<Lhs>, required_ctes_of_t<Rhs>>;
-  };
-
-  template <typename Flag, typename Lhs, typename Rhs>
-  struct required_static_ctes_of<cte_union_t<Flag, Lhs, Rhs>>
-  {
-       using type = typename std::conditional<
-        is_dynamic<Rhs>::value,
-        provided_static_ctes_of_t<Lhs>,
-        detail::type_vector_cat_t<provided_static_ctes_of_t<Lhs>, provided_static_ctes_of_t<Rhs>>>::type;
+    using type = detail::type_vector<Lhs, Rhs>;
   };
 
   // Interpreters
@@ -271,6 +261,12 @@ namespace sqlpp
   {
   };
 
+  template <typename NameTagProvider, typename Statement, typename... ColumnSpecs>
+  struct nodes_of<cte_t<NameTagProvider, Statement, ColumnSpecs...>> 
+  {
+    using type = Statement;
+  };
+
   template <typename NameTagProvider, typename Statement, typename... ColumnSpecs>
   struct provided_ctes_of<cte_t<NameTagProvider, Statement, ColumnSpecs...>>
   {
diff --git a/include/sqlpp11/core/clause/with.h b/include/sqlpp11/core/clause/with.h
index bd31a904..2c2a43a3 100644
--- a/include/sqlpp11/core/clause/with.h
+++ b/include/sqlpp11/core/clause/with.h
@@ -113,8 +113,6 @@ namespace sqlpp
     auto operator()(Statement statement)
         -> new_statement_t<consistent_t, typename Statement::_policies_t, no_with_t, with_t<Expressions...>>
     {
-#warning: check that no cte refers to any of the ctes to the right
-#warning: check that ctes have different names
       return {statement, _data};
     }
   };
@@ -135,11 +133,35 @@ namespace sqlpp
     return to_sql_string(context, t._data);
   }
 
+  // CTEs can depend on CTEs defined before (in the same query).
+  // `have_correct_dependencies` checks that by walking the CTEs from left to right and building a type vector that
+  // contains the CTE it already has looked at.
+  template <typename AllowedCTEs, typename... CTEs>
+    struct have_correct_dependencies_impl;
+
+  template <typename AllowedCTEs>
+    struct have_correct_dependencies_impl<AllowedCTEs>: public std::true_type {};
+
+  template <typename AllowedCTEs, typename CTE, typename... Rest>
+    struct have_correct_dependencies_impl<AllowedCTEs, CTE, Rest...>
+    {
+      using allowed_ctes = detail::type_vector_cat_t<AllowedCTEs, provided_ctes_of_t<CTE>>;
+      static constexpr bool value = allowed_ctes::template contains_all<required_ctes_of_t<CTE>>::value and
+                                    have_correct_dependencies_impl<allowed_ctes, Rest...>::value;
+    };
+
+  template <typename... CTEs>
+  struct have_correct_dependencies
+  {
+    static constexpr bool value = have_correct_dependencies_impl<detail::type_vector<>, CTEs...>::value;
+  };
   template <typename... Expressions>
   auto with(Expressions... cte) -> blank_with_t<Expressions...>
   {
     static_assert(logic::all<is_cte<Expressions>::value...>::value,
                   "at least one expression in with is not a common table expression");
+    static_assert(have_correct_dependencies<Expressions...>::value, "at least one CTE depends on another CTE that is not defined (yet)");
+#warning: check that ctes have different names
 #warning: Need to test that cte_t::as yields a cte_ref and that cte_ref is not a cte
     return {{cte...}};
   }
diff --git a/tests/core/serialize/clause/cte.cpp b/tests/core/serialize/clause/cte.cpp
index 60cc51cc..61e378cf 100644
--- a/tests/core/serialize/clause/cte.cpp
+++ b/tests/core/serialize/clause/cte.cpp
@@ -77,5 +77,19 @@ int main(int, char* [])
     SQLPP_COMPARE(all_of(y), "y.a");
   }
 
+  // A CTE depending on another CTE
+  {
+    const auto x = cte(sqlpp::alias::x).as(select(foo.id).from(foo).unconditionally());
+    const auto y = cte(sqlpp::alias::y).as(select(x.id, sqlpp::value(7).as(sqlpp::alias::a)).from(x).unconditionally());
+    const auto z = y.as(sqlpp::alias::z);
+    SQLPP_COMPARE(y, "y AS (SELECT x.id, 7 AS a FROM x)");
+    SQLPP_COMPARE(make_table_ref(y), "y");
+    SQLPP_COMPARE(y.id, "y.id");
+    SQLPP_COMPARE(z, "y AS z");
+    SQLPP_COMPARE(z.id, "z.id");
+    SQLPP_COMPARE(all_of(y), "y.id, y.a");
+    SQLPP_COMPARE(all_of(z), "z.id, z.a");
+  }
+
   return 0;
 }
diff --git a/tests/core/serialize/clause/with.cpp b/tests/core/serialize/clause/with.cpp
index 699b1826..836c93a6 100644
--- a/tests/core/serialize/clause/with.cpp
+++ b/tests/core/serialize/clause/with.cpp
@@ -108,5 +108,14 @@ int main(int, char* [])
     SQLPP_COMPARE(with(y, x), "WITH RECURSIVE y AS (SELECT tab_foo.id FROM tab_foo), x AS (SELECT 0 AS a UNION ALL SELECT (x.a + 1) AS a FROM x WHERE x.a < 10) ");
   }
 
+  // WITH two CTEs, second depends on first
+  {
+    const auto x = cte(sqlpp::alias::x).as(select(foo.id).from(foo).unconditionally());
+    const auto y = cte(sqlpp::alias::y).as(select(x.id).from(x).unconditionally());
+
+#warning: Need to test that CTEs have different names!
+    SQLPP_COMPARE(with(x, y), "WITH x AS (SELECT tab_foo.id FROM tab_foo), y AS (SELECT x.id FROM x) ");
+  }
+
   return 0;
 }