Fixes nlohmann#2728

includes some macros to be defined for using without file io.

include/nlohmann/detail/input/input_adapters.hpp

@@ -26,6 +26,7 @@ enum class input_format_t { json, cbor, msgpack, ubjson, bson };
 // input adapters //
 ////////////////////
 
+#ifndef JSON_NO_IO
 /*!
 Input adapter for stdio file access. This adapter read only 1 byte and do not use any
  buffer. This adapter is a very low level adapter.
@@ -115,6 +116,7 @@ class input_stream_adapter
     std::istream* is = nullptr;
     std::streambuf* sb = nullptr;
 };
+#endif  // JSON_NO_IO
 
 // General-purpose iterator-based adapter. It might not be as fast as
 // theoretically possible for some containers, but it is extremely versatile.
@@ -381,6 +383,7 @@ auto input_adapter(const ContainerType& container) -> decltype(input_adapter(beg
     return input_adapter(begin(container), end(container));
 }
 
+#ifndef JSON_NO_IO
 // Special cases with fast paths
 inline file_input_adapter input_adapter(std::FILE* file)
 {
@@ -396,6 +399,7 @@ inline input_stream_adapter input_adapter(std::istream&& stream)
 {
     return input_stream_adapter(stream);
 }
+#endif  // JSON_NO_IO
 
 using contiguous_bytes_input_adapter = decltype(input_adapter(std::declval<const char*>(), std::declval<const char*>()));
 

include/nlohmann/detail/output/output_adapters.hpp

@@ -50,6 +50,7 @@ class output_vector_adapter : public output_adapter_protocol<CharType>
     std::vector<CharType>& v;
 };
 
+#ifndef JSON_NO_IO
 /// output adapter for output streams
 template<typename CharType>
 class output_stream_adapter : public output_adapter_protocol<CharType>
@@ -73,6 +74,7 @@ class output_stream_adapter : public output_adapter_protocol<CharType>
   private:
     std::basic_ostream<CharType>& stream;
 };
+#endif  // JSON_NO_IO
 
 /// output adapter for basic_string
 template<typename CharType, typename StringType = std::basic_string<CharType>>
@@ -105,8 +107,10 @@ class output_adapter
     output_adapter(std::vector<CharType>& vec)
         : oa(std::make_shared<output_vector_adapter<CharType>>(vec)) {}
 
+#ifndef JSON_NO_IO
     output_adapter(std::basic_ostream<CharType>& s)
         : oa(std::make_shared<output_stream_adapter<CharType>>(s)) {}
+#endif  // JSON_NO_IO
 
     output_adapter(StringType& s)
         : oa(std::make_shared<output_string_adapter<CharType, StringType>>(s)) {}

include/nlohmann/json.hpp

@@ -6521,7 +6521,7 @@ class basic_json
 
     /// @name serialization
     /// @{
-
+#ifndef JSON_NO_IO
     /*!
     @brief serialize to stream
 
@@ -6581,7 +6581,7 @@ class basic_json
     {
         return o << j;
     }
-
+#endif  // JSON_NO_IO
     /// @}
 
 
@@ -6837,7 +6837,7 @@ class basic_json
                ? parser(std::move(ia), nullptr, true, ignore_comments).sax_parse(sax, strict)
                : detail::binary_reader<basic_json, decltype(ia), SAX>(std::move(ia)).sax_parse(format, sax, strict);
     }
-
+#ifndef JSON_NO_IO
     /*!
     @brief deserialize from stream
     @deprecated This stream operator is deprecated and will be removed in
@@ -6882,7 +6882,7 @@ class basic_json
         parser(detail::input_adapter(i)).parse(false, j);
         return i;
     }
-
+#endif // JSON_NO_IO
     /// @}
 
     ///////////////////////////