Utility: support C++17 std::string_view in Debug.

doc/corrade-changelog.dox

@@ -188,6 +188,8 @@ namespace Corrade {
 -   @cpp !Debug{} @ce or @ref Utility-Debug-source-location "source location output in Debug"
     is now enabled on MSVC 2019 16.6+ as well, making it available across all
     compilers
+-   @ref Utility::Debug now accepts also a C++17 @ref std::string_view if
+    you include @ref Corrade/Utility/DebugStlStringView.h
 -   @ref Utility::Directory::isDirectory() now follows symlinks on Unix
     platforms
 -   @ref Utility::Directory::Flag::SkipFiles and

src/Corrade/Utility/CMakeLists.txt

@@ -57,6 +57,7 @@ if(WITH_UTILITY)
         ConfigurationValue.h
         Debug.h
         DebugStl.h
+        DebugStlStringView.h
         Directory.h
         Endianness.h
         EndiannessBatch.h

src/Corrade/Utility/Debug.h

@@ -76,13 +76,22 @@ Support for printing more types can be added by implementing an overload of
 To optimize compile times, the @ref Corrade/Utility/Debug.h header provides
 only support for printing builtin types, generic iterable containers and
 @ref std::pair. Printing of @ref std::string and @ref std::tuple is possible if
-you @cpp #include @ce a separate @ref Corrade/Utility/DebugStl.h header. This
+you include @ref Corrade/Utility/DebugStl.h. The support is provided in a
+separate header to avoid unconditional @cpp #include <string> @ce or
+@cpp #include <tuple> @ce, which significantly affect compile times. This
 header also provides a fallback to @ref std::ostream @cpp operator<<() @ce
 overloads, if there's no @cpp operator<<() @ce implemented for printing given
 type using @ref Debug. Note that printing @ref std::vector or @ref std::map
 containers is already possible with the generic iterable container support in
 @ref Corrade/Utility/Debug.h.
 
+On compilers that support C++17 and @ref std::string_view, support for printing
+it is provided @ref Corrade/Utility/DebugStlStringView.h. For
+similar reasons, it's a dedicated header to avoid unconditional
+@cpp #include <string_view> @ce, but this one is even significantly heavier
+than the @ref string "<string>" etc. includes on certain implementations, so
+it's separate from the others as well.
+
 @section Utility-Debug-scoped-output Scoped output redirection
 
 Output specified in class constructor is used for all instances created during

src/Corrade/Utility/DebugStl.h

@@ -31,8 +31,10 @@
 @m_since{2019,10}
 
 Including this header allows you to use STL types such as @ref std::string or
-@ref std::tuple with @ref Corrade::Utility::Debug. See @ref Utility-Debug-stl
-for more information.
+@ref std::tuple with @ref Corrade::Utility::Debug. A separate
+@ref Corrade/Utility/DebugStlStringView.h header provides compatibility with
+@ref std::string_view from C++17. See @ref Utility-Debug-stl for more
+information.
 */
 
 #include <iosfwd>

src/Corrade/Utility/DebugStlStringView.h

@@ -0,0 +1,67 @@
+#ifndef Corrade_Utility_DebugStlStringView_h
+#define Corrade_Utility_DebugStlStringView_h
+/*
+    This file is part of Corrade.
+
+    Copyright © 2007, 2008, 2009, 2010, 2011, 2012, 2013, 2014, 2015, 2016,
+                2017, 2018, 2019, 2020, 2021, 2022
+              Vladimír Vondruš <mosra@centrum.cz>
+
+    Permission is hereby granted, free of charge, to any person obtaining a
+    copy of this software and associated documentation files (the "Software"),
+    to deal in the Software without restriction, including without limitation
+    the rights to use, copy, modify, merge, publish, distribute, sublicense,
+    and/or sell copies of the Software, and to permit persons to whom the
+    Software is furnished to do so, subject to the following conditions:
+
+    The above copyright notice and this permission notice shall be included
+    in all copies or substantial portions of the Software.
+
+    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+    THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+    LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+    FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+    DEALINGS IN THE SOFTWARE.
+*/
+
+/** @file
+@brief STL @ref std::string_view compatibility for @ref Corrade::Utility::Debug
+@m_since_latest
+
+Including this header allows you to use a C++17 @ref std::string_view with
+@ref Corrade::Utility::Debug. A separate @ref Corrade/Utility/DebugStl.h header
+provides compatibility with @ref std::string or @ref std::tuple. See
+@ref Utility-Debug-stl for more information.
+*/
+
+#include <string_view>
+
+#include "Corrade/Containers/ArrayView.h"
+#include "Corrade/Containers/StringView.h"
+#include "Corrade/Utility/Debug.h"
+
+namespace Corrade { namespace Utility {
+
+/** @relatesalso Debug
+@brief Print a @ref std::string_view to debug output
+@m_since_latest
+*/
+inline Debug& operator<<(Debug& debug, std::string_view value) {
+    return debug << Containers::StringView{value.data(), value.size()};
+}
+
+/** @relatesalso Debug
+@brief Print a @ref std::basic_string_view to debug output
+@m_since_latest
+
+All other types than exactly @ref std::string_view are printed as containers.
+*/
+template<class T> Debug& operator<<(Debug& debug, std::basic_string_view<T> value) {
+    return debug << Containers::ArrayView<const T>{value.data(), value.size()};
+}
+
+}}
+
+#endif

src/Corrade/Utility/Test/CMakeLists.txt

@@ -171,9 +171,11 @@ if(NOT CMAKE_CXX_FLAGS MATCHES "-std=")
        (CMAKE_CXX_COMPILER_ID STREQUAL "Clang" AND NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS "5.0") OR
        (CMAKE_CXX_COMPILER_ID STREQUAL "AppleClang" AND NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS "9.3") OR
        (CMAKE_CXX_COMPILER_ID STREQUAL "MSVC" AND NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS "19.10"))
+        corrade_add_test(UtilityDebugStlStringViewTest DebugStlStringViewTest.cpp)
         corrade_add_test(UtilityFormatStlStringViewTest FormatStlStringViewTest.cpp)
         corrade_add_test(UtilityMacrosCpp17Test MacrosCpp17Test.cpp)
         set_target_properties(
+            UtilityDebugStlStringViewTest
             UtilityFormatStlStringViewTest
             UtilityMacrosCpp17Test
             PROPERTIES

src/Corrade/Utility/Test/DebugStlStringViewTest.cpp

@@ -0,0 +1,64 @@
+/*
+    This file is part of Corrade.
+
+    Copyright © 2007, 2008, 2009, 2010, 2011, 2012, 2013, 2014, 2015, 2016,
+                2017, 2018, 2019, 2020, 2021, 2022
+              Vladimír Vondruš <mosra@centrum.cz>
+
+    Permission is hereby granted, free of charge, to any person obtaining a
+    copy of this software and associated documentation files (the "Software"),
+    to deal in the Software without restriction, including without limitation
+    the rights to use, copy, modify, merge, publish, distribute, sublicense,
+    and/or sell copies of the Software, and to permit persons to whom the
+    Software is furnished to do so, subject to the following conditions:
+
+    The above copyright notice and this permission notice shall be included
+    in all copies or substantial portions of the Software.
+
+    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+    THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+    LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+    FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+    DEALINGS IN THE SOFTWARE.
+*/
+
+#include <sstream>
+
+#include "Corrade/TestSuite/Tester.h"
+#include "Corrade/Utility/DebugStl.h"
+#include "Corrade/Utility/DebugStlStringView.h"
+
+namespace Corrade { namespace Utility { namespace Test { namespace {
+
+struct DebugStlStringViewTest: TestSuite::Tester {
+    explicit DebugStlStringViewTest();
+
+    void test();
+    void testEmpty();
+};
+
+DebugStlStringViewTest::DebugStlStringViewTest() {
+    addTests({&DebugStlStringViewTest::test,
+              &DebugStlStringViewTest::testEmpty});
+}
+
+using namespace std::string_view_literals;
+
+void DebugStlStringViewTest::test() {
+    std::ostringstream out;
+    Debug{&out} << "hello\0world!"sv;
+    CORRADE_COMPARE(out.str(), (std::string{"hello\0world!\n", 13}));
+}
+
+void DebugStlStringViewTest::testEmpty() {
+    std::ostringstream out;
+    /* Empty string view should not cause any issues with data access */
+    Debug{&out} << "hello" << std::string_view{} << "!";
+    CORRADE_COMPARE(out.str(), "hello  !\n");
+}
+
+}}}}
+
+CORRADE_TEST_MAIN(Corrade::Utility::Test::DebugStlStringViewTest)