Add configuration nsel_CONFIG_WIN32_LEAN_AND_MEAN (proposed in #69, t…

…hanks @No-needto-recall)

README.md

@@ -112,7 +112,12 @@ At default, *expected lite* uses `std::expected` if it is available and lets you
 Define this to `nsel_EXPECTED_STD` to select `std::expected` as `nonstd::expected`. Define this to `nsel_EXPECTED_NONSTD` to select `nonstd::expected` as `nonstd::expected`. Default is undefined, which has the same effect as defining to `nsel_EXPECTED_DEFAULT`.
 
 -D<b>nsel\_P0323R</b>=7  *(default)*  
-Define this to the proposal revision number to control the presence and behavior of features (see tables). Default is 7 for the latest revision.   
+Define this to the proposal revision number to control the presence and behavior of features (see tables). Default is 7 for the latest revision.
+
+#### Define `WIN32_LEAN_AND_MEAN`
+
+-D<b>nsel\_CONFIG\_WIN32\_LEAN\_AND\_MEAN</b>=1  
+Define this to 0 if you want to omit automatic definition of `WIN32_LEAN_AND_MEAN`. Default is 1 when `_MSC_VER` is present.
 
 #### Disable C++ exceptions
 

include/nonstd/expected.hpp

@@ -81,6 +81,12 @@
 # define nsel_P2505R  5
 #endif
 
+// Lean and mean inclusion of Windows.h, if applicable; default on for MSVC:
+
+#if !defined(nsel_CONFIG_WIN32_LEAN_AND_MEAN) && defined(_MSC_VER)
+# define nsel_CONFIG_WIN32_LEAN_AND_MEAN  1
+#endif
+
 // Control presence of C++ exception handling (try and auto discover):
 
 #ifndef nsel_CONFIG_NO_EXCEPTIONS
@@ -277,6 +283,12 @@ namespace nonstd {
 
 // additional includes:
 
+#if nsel_CONFIG_WIN32_LEAN_AND_MEAN
+# ifndef  WIN32_LEAN_AND_MEAN
+#  define WIN32_LEAN_AND_MEAN
+# endif
+#endif
+
 #if nsel_CONFIG_NO_EXCEPTIONS
 # if nsel_CONFIG_NO_EXCEPTIONS_SEH
 #  include <windows.h>   // for ExceptionCodes

test/expected-main.t.cpp

@@ -10,6 +10,9 @@
 #define expected_PRESENT( x ) \
     std::cout << #x << ": " << x << "\n"
 
+#define expected_DEFINED( x ) \
+    std::cout << #x << ": (defined)\n"
+
 #define expected_ABSENT( x ) \
     std::cout << #x << ": (undefined)\n"
 
@@ -35,15 +38,17 @@ CASE( "expected-lite version" "[.expected][.version]" )
     expected_PRESENT( expected_lite_VERSION );
 }
 
-CASE( "any configuration" "[.expected][.config]" )
+CASE( "expected-lite configuration" "[.expected][.config]" )
 {
     expected_PRESENT( nsel_HAVE_STD_EXPECTED );
     expected_PRESENT( nsel_USES_STD_EXPECTED );
     expected_PRESENT( nsel_EXPECTED_DEFAULT );
     expected_PRESENT( nsel_EXPECTED_NONSTD );
     expected_PRESENT( nsel_EXPECTED_STD );
     expected_PRESENT( nsel_CONFIG_SELECT_EXPECTED );
+    expected_PRESENT( nsel_CONFIG_WIN32_LEAN_AND_MEAN );
     expected_PRESENT( nsel_CONFIG_NO_EXCEPTIONS );
+    expected_PRESENT( nsel_CONFIG_NO_EXCEPTIONS_SEH );
     expected_PRESENT( nsel_CPLUSPLUS );
 }
 
@@ -84,6 +89,12 @@ CASE( "presence of C++ library features" "[.stdlibrary]" )
     std::cout << "(Presence of C++ library features not available: using std::expected)\n";
 #else
 
+#ifdef WIN32_LEAN_AND_MEAN
+    expected_DEFINED( WIN32_LEAN_AND_MEAN );
+#else
+    expected_ABSENT(  WIN32_LEAN_AND_MEAN );
+#endif
+
 #ifdef __cpp_exceptions
     expected_PRESENT( __cpp_exceptions );
 #else