Better support for infs and NaNs in JSON writer

As the types and values sent into the writer are determined by Catch2,
I do not expect to actually need this support, but it is better to have
it and not be surprised in the future.

src/catch2/internal/catch_jsonwriter.cpp

@@ -7,8 +7,10 @@
 // SPDX-License-Identifier: BSL-1.0
 #include <catch2/internal/catch_enforce.hpp>
 #include <catch2/internal/catch_jsonwriter.hpp>
+#include <catch2/internal/catch_polyfills.hpp>
 #include <catch2/internal/catch_unreachable.hpp>
 
+#include <cmath>
 #include <locale>
 
 namespace Catch {
@@ -145,10 +147,30 @@ namespace Catch {
         writeImpl( value, true );
     }
 
+    void JsonValueWriter::write( float value ) && {
+        writeFloatingPoint( value );
+    }
+
+    void JsonValueWriter::write( double value ) && {
+        writeFloatingPoint( value );
+    }
+
     void JsonValueWriter::write( bool value ) && {
         writeImpl( value ? "true"_sr : "false"_sr, false );
     }
 
+    template <typename T>
+    void JsonValueWriter::writeFloatingPoint( T value ) {
+        if ( Catch::isnan( value ) ) {
+            writeImpl( "NaN"_sr, false );
+        } else if ( std::isinf( value ) ) {
+            writeImpl( value < 0 ? "-Infinity"_sr : "Infinity"_sr, false );
+        } else {
+            m_sstream << value;
+            writeImpl( m_sstream.str(), false );
+        }
+    }
+
     void JsonValueWriter::writeImpl( Catch::StringRef value, bool quote ) {
         if ( quote ) { m_os << '"'; }
         size_t current_start = 0;

src/catch2/internal/catch_jsonwriter.hpp

@@ -39,11 +39,19 @@ namespace Catch {
             writeImpl( value, !std::is_arithmetic<T>::value );
         }
         void write( StringRef value ) &&;
+        void write( float value ) &&;
+        void write( double value ) &&;
         void write( bool value ) &&;
 
     private:
         void writeImpl( StringRef value, bool quote );
 
+        // Helper to deal with non-finite floating point values, which
+        // are not standard JSON, but we use JS/Python/etc. approach of
+        // emitting `NaN`, `Infinity`, `-Infinity` as number(like).
+        template <typename T>
+        void writeFloatingPoint( T value );
+
         // Without this SFINAE, this overload is a better match
         // for `std::string`, `char const*`, `char const[N]` args.
         // While it would still work, it would cause code bloat