Added several tests for static_assert (plus fixes for aggregates)

tests/Aggregates.cpp

@@ -31,15 +31,80 @@
 #include <sqlpp11/functions.h>
 #include <sqlpp11/connection.h>
 
+namespace sqlpp
+{
+  namespace test
+  {
+    template <typename T>
+    void print_type_on_error(std::true_type, const T&)
+    {
+    }
+
+    template <typename T>
+    void print_type_on_error(std::false_type, const T& t)
+    {
+      t._print_me_;
+    }
+
+    template <typename Assert, typename Expression>
+    void run_check(const Expression&)
+    {
+      using Context = MockDb::_serializer_context_t;
+      using CheckResult = std::is_same<sqlpp::run_check_t<Context, Expression>, Assert>;
+      static_assert(CheckResult::value, "Unexpected run_check result");
+      print_type_on_error(CheckResult{}, sqlpp::run_check_t<Context, Expression>{});
+    }
+
+    template <typename Expression>
+    void run_check(const Expression&)
+    {
+      using Context = MockDb::_serializer_context_t;
+      using CheckResult = std::is_same<sqlpp::run_check_t<Context, Expression>, consistent_t>;
+      static_assert(CheckResult::value, "Unexpected run_check result");
+      print_type_on_error(CheckResult{}, sqlpp::run_check_t<Context, Expression>{});
+    }
+  }
+}
+
+SQLPP_ALIAS_PROVIDER(whatever);
+
 int Aggregates(int, char**)
 {
-  MockDb db = {};
-  MockDb::_serializer_context_t printer;
+  using sqlpp::test::run_check;
 
   // test::TabFoo f;
   test::TabBar t;
 
-  db(select(t.alpha).from(t).where(true).group_by(t.alpha));
+  // If there is no group_by, we can select whatever we want
+  run_check(select(all_of(t)).from(t).where(true));
+  run_check(select(t.alpha).from(t).where(true));
+  run_check(select(count(t.alpha)).from(t).where(true));
+
+  // If there is a static group_by, selected columns must be made of group_by expressions, or aggregate expression (e.g.
+  // count(t.id)) or values to be valid
+  run_check(select(t.alpha).from(t).where(true).group_by(t.alpha));
+  run_check(select((t.alpha + 42).as(whatever)).from(t).where(true).group_by(t.alpha));
+  run_check(select((t.alpha + 42).as(whatever)).from(t).where(true).group_by(t.alpha, t.alpha + t.delta * 17));
+  run_check(
+      select((t.alpha + t.delta * 17).as(whatever)).from(t).where(true).group_by(t.alpha, t.alpha + t.delta * 17));
+  run_check(select((t.beta + "fortytwo").as(whatever)).from(t).where(true).group_by(t.beta));
+
+  run_check(select(avg(t.alpha)).from(t).where(true).group_by(t.beta));
+  run_check(select(count(t.alpha)).from(t).where(true).group_by(t.beta));
+  run_check(select(max(t.alpha)).from(t).where(true).group_by(t.beta));
+  run_check(select(min(t.alpha)).from(t).where(true).group_by(t.beta));
+  run_check(select(sum(t.alpha)).from(t).where(true).group_by(t.beta));
+
+  run_check(select((t.alpha + count(t.delta)).as(whatever)).from(t).where(true).group_by(t.alpha));
+
+  run_check(select(sqlpp::value(1).as(whatever)).from(t).where(true).group_by(t.alpha));
+  run_check(select(sqlpp::value("whatever").as(whatever)).from(t).where(true).group_by(t.alpha));
+
+  // Otherwise, they are invalid
+  run_check<sqlpp::assert_aggregates_t>(select(t.beta).from(t).where(true).group_by(t.alpha));
+  run_check<sqlpp::assert_aggregates_t>(select((t.alpha + t.delta).as(whatever)).from(t).where(true).group_by(t.alpha));
+  run_check<sqlpp::assert_aggregates_t>(
+      select((t.alpha + t.delta).as(whatever)).from(t).where(true).group_by(t.alpha, t.alpha + t.delta * 17));
 
   return 0;
 }