fix build with clang -std=c++20 (#216)

* apply llvm-namespace-comment

* Make jinja2cpp compilable under clang 12 with -std=c++20
the problem arose from the fact that libfmt switched to consteval check of format
string(that is great, but makes us obliged to provide format_to with
constexpr format_string or fmt::runtime overload)

unfortunatelly I couldn't make it work with constexpr std::string
so multistringliteral returns std::basic_string_view except for cases
where it needs std::string

fix #213

Author: rmorozov

.github/workflows/linux-build.yml

@@ -3,10 +3,16 @@ name: CI-linux-build
 
 on:
   push:
+    branches:
+      - master
+      - main
     paths-ignore:
       - 'docs/**'
       - '**.md'
   pull_request:
+    branches:
+      - master
+      - main
     paths-ignore:
       - 'docs/**'
       - '**.md'
@@ -96,7 +102,7 @@ jobs:
       fail-fast: false
       max-parallel: 8
       matrix:
-        compiler: [10, 11]
+        compiler: [10, 11, 12]
         base-flags: ["", -DJINJA2CPP_CXX_STANDARD=17]
         build-config: [Release, Debug]
         build-shared: [TRUE, FALSE]
@@ -106,6 +112,9 @@ jobs:
             docker-image: conanio/clang10
           - compiler: 11
             docker-image: conanio/clang11
+          - compiler: 12
+            docker-image: conanio/clang12-ubuntu16.04:1.39.0
+
 
     steps:
     - uses: actions/checkout@v1
@@ -119,12 +128,17 @@ jobs:
         INPUT_BUILD_SHARED: ${{ matrix.build-shared }}
         HOME: /home/conan
       run: |
+        #!/bin/bash
         set -ex
         export BUILD_TARGET=all
         export CMAKE_OPTS=-DCMAKE_VERBOSE_MAKEFILE=OFF
         export BUILD_CONFIG=${INPUT_BASE_CONFIG}
         export WORKSPACE=$GITHUB_WORKSPACE
-        $CXX --version
+        #if [ "${INPUT_COMPILER}" != "" ]; then export CXX=${INPUT_COMPILER}; fi
+        if [ "${INPUT_COMPILER}" == "clang-12" ] ; then
+        export INPUT_BASE_FLAGS="-DJINJA2CPP_CXX_STANDARD=20" ;
+        fi
+        #$CXX --version
         export EXTRA_FLAGS="${INPUT_BASE_FLAGS} ${INPUT_EXTRA_FLAGS}"
         mkdir $BUILD_DIRECTORY && cd $BUILD_DIRECTORY
         sudo chmod gou+rw -R $WORKSPACE

.github/workflows/windows-build.yml

@@ -2,10 +2,16 @@ name: CI-windows-build
 
 on:
   push:
+    branches:
+      - master
+      - main
     paths-ignore:
       - 'docs/**'
       - '**.md'
   pull_request:
+    branches:
+      - master
+      - main
     paths-ignore:
       - 'docs/**'
       - '**.md'

src/error_info.cpp

@@ -18,7 +18,12 @@ struct ValueRenderer
     {
     }
 
-    void operator()(bool val) const { fmt::format_to(ctx->out(), (val ? UNIVERSAL_STR("True") : UNIVERSAL_STR("False")).GetValue<CharT>()); }
+    constexpr void operator()(bool val) const {
+        fmt::format_to(
+                ctx->out(),
+                UNIVERSAL_STR("{}").GetValue<CharT>(),
+                (val ? UNIVERSAL_STR("True").GetValue<CharT>(): UNIVERSAL_STR("False").GetValue<CharT>()));
+    }
     void operator()(const jinja2::EmptyValue&) const { fmt::format_to(ctx->out(), UNIVERSAL_STR("").GetValue<CharT>()); }
     template<typename CharU>
     void operator()(const std::basic_string<CharU>& val) const
@@ -83,7 +88,7 @@ struct ValueRenderer
         fmt::format_to(ctx->out(), UNIVERSAL_STR("{}").GetValue<CharT>(), val);
     }
 };
-}
+} // namespace
 
 namespace fmt
 {
@@ -103,7 +108,7 @@ struct formatter<jinja2::Value, CharT>
         return fmt::format_to(ctx.out(), UNIVERSAL_STR("").GetValue<CharT>());
     }
 };
-}
+} // namespace fmt
 
 namespace jinja2
 {
@@ -281,4 +286,4 @@ std::wostream& operator << (std::wostream& os, const ErrorInfoW& res)
     os << res.ToString();
     return os;
 }
-} // jinja2
+} // namespace jinja2

src/expression_evaluator.cpp

@@ -596,5 +596,5 @@ CallParams EvaluateCallParams(const CallParamsInfo& info, RenderContext& context
     return result;
 }
 
-}
-}
+} // namespace helpers
+} // namespace jinja2

src/expression_parser.cpp

@@ -603,4 +603,4 @@ ExpressionParser::ParseResult<ExpressionEvaluatorPtr<IfExpression>> ExpressionPa
     return result;
 }
 
-} // jinja2
+} // namespace jinja2

src/filesystem_handler.cpp

@@ -144,4 +144,4 @@ CharFileStreamPtr RealFileSystem::OpenByteStream(const std::string& name) const
     return CharFileStreamPtr(nullptr, [](std::istream*){});
 }
 
-} // jinja2
+} // namespace jinja2

src/filters.cpp

@@ -1082,5 +1082,5 @@ InternalValue UserDefinedFilter::Filter(const InternalValue& baseVal, RenderCont
     return callable->GetExpressionCallable()(callParams, context);
 }
 
-} // filters
-} // jinja2
+} // namespace filters
+} // namespace jinja2

src/helpers.h

@@ -15,10 +15,27 @@ struct MultiStringLiteral
     const char* charValue;
     const wchar_t* wcharValue;
 
+    constexpr MultiStringLiteral(const char* val, const wchar_t* wval)
+        : charValue(val)
+        , wcharValue(wval)
+    {
+    }
+
+    template<typename CharT>
+    constexpr auto GetValue() const
+    {
+#if __cplusplus < 202002L
+        return GetValueStr<CharT>();
+#else
+        constexpr auto memPtr = SelectMemberPtr<CharT, &MultiStringLiteral::charValue, &MultiStringLiteral::wcharValue>::GetPtr();
+        return nonstd::basic_string_view<CharT>(this->*memPtr);
+#endif
+    }
+
     template<typename CharT>
-    auto GetValue() const
+    constexpr auto GetValueStr() const
     {
-        auto memPtr = SelectMemberPtr<CharT, &MultiStringLiteral::charValue, &MultiStringLiteral::wcharValue>::GetPtr();
+        constexpr auto memPtr = SelectMemberPtr<CharT, &MultiStringLiteral::charValue, &MultiStringLiteral::wcharValue>::GetPtr();
         return std::basic_string<CharT>(this->*memPtr);
     }
 
@@ -28,13 +45,13 @@ struct MultiStringLiteral
     template<const char* (MultiStringLiteral::*charMemPtr), const wchar_t* (MultiStringLiteral::*wcharMemPtr)>
     struct SelectMemberPtr<char, charMemPtr, wcharMemPtr>
     {
-        static auto GetPtr() {return charMemPtr;}
+        static constexpr auto GetPtr() {return charMemPtr;}
     };
 
     template<const char* (MultiStringLiteral::*charMemPtr), const wchar_t* (MultiStringLiteral::*wcharMemPtr)>
     struct SelectMemberPtr<wchar_t, charMemPtr, wcharMemPtr>
     {
-        static auto GetPtr() {return wcharMemPtr;}
+        static constexpr auto GetPtr() {return wcharMemPtr;}
     };
 
     template<typename CharT>

src/internal_value.cpp

@@ -859,6 +859,6 @@ InputValueConvertor::result_t InputValueConvertor::ConvertUserCallable(const Use
     }));
 }
 
-} // visitors
+} // namespace visitors
 
-} // jinja2
+} // namespace jinja2

src/lexer.cpp

@@ -119,4 +119,4 @@ bool Lexer::ProcessString(const lexertk::token&, Token& newToken)
     return true;
 }
 
-} // jinja2
+} // namespace jinja2