Add is_equal_or_null(col, some_value_or_null)

This replaces the former implicit tvin logic with an explicit function.

Author: rbock

include/sqlpp11/functions.h

@@ -47,6 +47,7 @@
 #include <sqlpp11/verbatim_table.h>
 #include <sqlpp11/value.h>
 #include <sqlpp11/value_or_null.h>
+#include <sqlpp11/is_equal_to_or_null.h>
 #include <sqlpp11/eval.h>
 
 namespace sqlpp

include/sqlpp11/is_equal_to_or_null.h

@@ -0,0 +1,85 @@
+/*
+ * Copyright (c) 2021, Roland Bock
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without modification,
+ * are permitted provided that the following conditions are met:
+ *
+ *   Redistributions of source code must retain the above copyright notice, this
+ *   list of conditions and the following disclaimer.
+ *
+ *   Redistributions in binary form must reproduce the above copyright notice, this
+ *   list of conditions and the following disclaimer in the documentation and/or
+ *   other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR
+ * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
+ * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef SQLPP11_IS_EQUAL_TO_OR_NULL_H
+#define SQLPP11_IS_EQUAL_TO_OR_NULL_H
+
+#include <sqlpp11/value_or_null.h>
+
+namespace sqlpp
+{
+  template <typename Expr, typename ValueType>
+  struct is_equal_to_or_null_t: public expression_operators<is_equal_to_or_null_t<Expr, ValueType>, boolean>,
+                     public alias_operators<is_equal_to_or_null_t<Expr, ValueType>>
+  {
+    using _traits = make_traits<boolean, tag::is_expression>;
+    using _nodes = detail::type_vector<Expr, value_or_null_t<ValueType>>;
+
+    is_equal_to_or_null_t(Expr expr, value_or_null_t<ValueType> value) : _expr(expr), _value(value)
+    {
+    }
+
+    is_equal_to_or_null_t(const is_equal_to_or_null_t&) = default;
+    is_equal_to_or_null_t(is_equal_to_or_null_t&&) = default;
+    is_equal_to_or_null_t& operator=(const is_equal_to_or_null_t&) = default;
+    is_equal_to_or_null_t& operator=(is_equal_to_or_null_t&&) = default;
+    ~is_equal_to_or_null_t() = default;
+
+
+    Expr _expr;
+    value_or_null_t<ValueType> _value;
+  };
+
+  template <typename Context, typename Expr, typename ValueType>
+  struct serializer_t<Context, is_equal_to_or_null_t<Expr, ValueType>>
+  {
+    using _serialize_check = consistent_t;
+    using Operand = is_equal_to_or_null_t<Expr, ValueType>;
+
+    static Context& _(const Operand& t, Context& context)
+    {
+      if (t._value._is_null)
+        serialize(t._expr.is_null(), context);
+      else
+        serialize(t._expr == t._value, context);
+
+      return context;
+    }
+  };
+
+  template <typename Expr, typename ValueType>
+  auto is_equal_to_or_null(Expr expr, value_or_null_t<ValueType> value) -> is_equal_to_or_null_t<Expr, ValueType>
+  {
+    static_assert(is_expression_t<Expr>::value,
+                  "is_equal_to_or_null() is to be called an expression (e.g. a column) and a value_or_null expression");
+    static_assert(std::is_same<value_type_of<Expr>, ValueType>::value,
+                  "is_equal_to_or_null() arguments need to have the same value type");
+    return {expr, value};
+  }
+
+}  // namespace sqlpp
+
+#endif

include/sqlpp11/is_not_null.h

@@ -78,8 +78,9 @@ namespace sqlpp
 
     static Context& _(const T& t, Context& context)
     {
+      context << "(";
       serialize_operand(t._operand, context);
-      context << " IS NOT NULL";
+      context << " IS NOT NULL)";
       return context;
     }
   };

include/sqlpp11/is_null.h

@@ -78,8 +78,9 @@ namespace sqlpp
 
     static Context& _(const T& t, Context& context)
     {
+      context << "(";
       serialize_operand(t._operand, context);
-      context << " IS NULL";
+      context << " IS NULL)";
       return context;
     }
   };

test_serializer/Where.cpp

@@ -63,8 +63,11 @@ int Where(int, char*[])
   // Sometimes
   compare(__LINE__, where(bar.gamma), " WHERE tab_bar.gamma");
   compare(__LINE__, where(bar.gamma == false), " WHERE (tab_bar.gamma=" + getFalse() + ")");
-  compare(__LINE__, where(bar.beta.is_null()), " WHERE tab_bar.beta IS NULL");
+  compare(__LINE__, where(bar.beta.is_null()), " WHERE (tab_bar.beta IS NULL)");
   compare(__LINE__, where(bar.beta == "SQL"), " WHERE (tab_bar.beta='SQL')");
+  compare(__LINE__, where(is_equal_to_or_null(bar.beta, ::sqlpp::value_or_null("SQL"))), " WHERE (tab_bar.beta='SQL')");
+  compare(__LINE__, where(is_equal_to_or_null(bar.beta, ::sqlpp::value_or_null<sqlpp::text>(::sqlpp::null))),
+          " WHERE (tab_bar.beta IS NULL)");
 #if __cplusplus >= 201703L
   // string_view argument
   std::string_view sqlString = "SQL";