Add StringMaker for std::(w)string_view

Fixes #1375

docs/configuration.md

@@ -127,6 +127,7 @@ Catch's selection, by defining either `CATCH_CONFIG_CPP11_TO_STRING` or
 ## C++17 toggles
 
     CATCH_CONFIG_CPP17_UNCAUGHT_EXCEPTIONS  // Use std::uncaught_exceptions instead of std::uncaught_exception
+    CATCH_CONFIG_CPP17_STRING_VIEW          // Provide StringMaker specialization for std::string_view
 
 Catch contains basic compiler/standard detection and attempts to use
 some C++17 features whenever appropriate. This automatic detection

include/internal/catch_compiler_capabilities.h

@@ -29,11 +29,11 @@
 
 #ifdef __cplusplus
 
-#  if __cplusplus >= 201402L
+#  if (__cplusplus >= 201402L) || (defined(_MSVC_LANG) && _MSVC_LANG >= 201402L)
 #    define CATCH_CPP14_OR_GREATER
 #  endif
 
-#  if __cplusplus >= 201703L
+#  if (__cplusplus >= 201703L) || (defined(_MSVC_LANG) && _MSVC_LANG >= 201703L)
 #    define CATCH_CPP17_OR_GREATER
 #  endif
 
@@ -154,6 +154,16 @@
     #define CATCH_INTERNAL_CONFIG_COUNTER
 #endif
 
+////////////////////////////////////////////////////////////////////////////////
+// Check if string_view is available and usable
+// The check is split apart to work around v140 (VS2015) preprocessor issue...
+#if defined(__has_include)
+#if __has_include(<string_view>) && defined(CATCH_CPP17_OR_GREATER)
+#    define CATCH_INTERNAL_CONFIG_CPP17_STRING_VIEW
+#endif
+#endif
+
+
 #if defined(CATCH_INTERNAL_CONFIG_COUNTER) && !defined(CATCH_CONFIG_NO_COUNTER) && !defined(CATCH_CONFIG_COUNTER)
 #   define CATCH_CONFIG_COUNTER
 #endif
@@ -177,6 +187,10 @@
 #  define CATCH_CONFIG_CPP17_UNCAUGHT_EXCEPTIONS
 #endif
 
+#if defined(CATCH_INTERNAL_CONFIG_CPP17_STRING_VIEW) && !defined(CATCH_CONFIG_NO_CPP17_STRING_VIEW) && !defined(CATCH_CONFIG_CPP17_STRING_VIEW)
+#  define CATCH_CONFIG_CPP17_STRING_VIEW
+#endif
+
 #if defined(CATCH_CONFIG_EXPERIMENTAL_REDIRECT)
 #  define CATCH_INTERNAL_CONFIG_NEW_CAPTURE
 #endif

include/internal/catch_tostring.cpp

@@ -116,14 +116,9 @@ std::string StringMaker<std::string>::convert(const std::string& str) {
     return s;
 }
 
-#ifdef CATCH_CONFIG_WCHAR
-std::string StringMaker<std::wstring>::convert(const std::wstring& wstr) {
-    std::string s;
-    s.reserve(wstr.size());
-    for (auto c : wstr) {
-        s += (c <= 0xff) ? static_cast<char>(c) : '?';
-    }
-    return ::Catch::Detail::stringify(s);
+#ifdef CATCH_CONFIG_CPP17_STRING_VIEW
+std::string StringMaker<std::string_view>::convert(std::string_view str) {
+    return ::Catch::Detail::stringify(std::string{ str });
 }
 #endif
 
@@ -141,7 +136,23 @@ std::string StringMaker<char*>::convert(char* str) {
         return{ "{null string}" };
     }
 }
+
 #ifdef CATCH_CONFIG_WCHAR
+std::string StringMaker<std::wstring>::convert(const std::wstring& wstr) {
+    std::string s;
+    s.reserve(wstr.size());
+    for (auto c : wstr) {
+        s += (c <= 0xff) ? static_cast<char>(c) : '?';
+    }
+    return ::Catch::Detail::stringify(s);
+}
+
+# ifdef CATCH_CONFIG_CPP17_STRING_VIEW
+std::string StringMaker<std::wstring_view>::convert(std::wstring_view str) {
+    return StringMaker<std::wstring>::convert(std::wstring(str));
+}
+# endif
+
 std::string StringMaker<wchar_t const*>::convert(wchar_t const * str) {
     if (str) {
         return ::Catch::Detail::stringify(std::wstring{ str });

include/internal/catch_tostring.h

@@ -16,6 +16,10 @@
 #include "catch_compiler_capabilities.h"
 #include "catch_stream.h"
 
+#ifdef CATCH_CONFIG_CPP17_STRING_VIEW
+#include <string_view>
+#endif
+
 #ifdef __OBJC__
 #include "catch_objc_arc.hpp"
 #endif
@@ -152,10 +156,11 @@ namespace Catch {
     struct StringMaker<std::string> {
         static std::string convert(const std::string& str);
     };
-#ifdef CATCH_CONFIG_WCHAR
+
+#ifdef CATCH_CONFIG_CPP17_STRING_VIEW
     template<>
-    struct StringMaker<std::wstring> {
-        static std::string convert(const std::wstring& wstr);
+    struct StringMaker<std::string_view> {
+        static std::string convert(std::string_view str);
     };
 #endif
 
@@ -169,6 +174,18 @@ namespace Catch {
     };
 
 #ifdef CATCH_CONFIG_WCHAR
+    template<>
+    struct StringMaker<std::wstring> {
+        static std::string convert(const std::wstring& wstr);
+    };
+
+# ifdef CATCH_CONFIG_CPP17_STRING_VIEW
+    template<>
+    struct StringMaker<std::wstring_view> {
+        static std::string convert(std::wstring_view str);
+    };
+# endif
+
     template<>
     struct StringMaker<wchar_t const *> {
         static std::string convert(wchar_t const * str);

projects/SelfTest/UsageTests/ToStringGeneral.tests.cpp

@@ -116,6 +116,18 @@ TEST_CASE("Static arrays are convertible to string", "[toString]") {
     }
 }
 
+#ifdef CATCH_CONFIG_CPP17_STRING_VIEW
+
+TEST_CASE("String views are stringified like other strings", "[toString][approvals]") {
+    std::string_view view{"abc"};
+    CHECK(Catch::Detail::stringify(view) == R"("abc")");
+
+    std::string_view arr[] { view };
+    CHECK(Catch::Detail::stringify(arr) == R"({ "abc" })");
+}
+
+#endif
+
 namespace {
 
 struct WhatException : std::exception {