System.InvalidOperationException : Invalid primitive System.Char

[zacala1]

When I tested serializing char type property, 'System.InvalidOperationException : Invalid primitive System.Char' exception occurred.
I guess that 'private void WritePrimitive(object primitive, TomlPropertyDisplayKind displayKind)' function should deal with char type. there is no 'if (primitive is char c)' condition.

[xoofx]

Indeed. I have no personal incentive to fix this, but PR Welcome. It needs to handle correctly the mapping back and forth to strings and handle the case that one UTF-8 char might not be able to match to a single UTF-16 char as you would need surrogates pairs, so yeah, supporting a char is not great in the end.

[markusschaber]

As a C# "char" could be a lone surrogate, they cannot be always properly output as UTF-8 strings. On the other hand, how should the parser react to input strings which do not map to a single char, like empty strings, or strings which contain several characters?

Maybe it would be better to use the numeric value of the char and output it as an integer (treating it equal to .NET ushort / uint16)?

[lilith]

There's no 'char' type in either TOML or JSON. And .NET's strings are not even UTF-16, but rather WTF-16, so you can't make assumptions about anything being valid.

I would suggest either explicitly preventing this from working by default (requiring a custom type converter for people who want to opt into that can of worms), or serializing it as integer. Deserializing it as integer is also kind of fraught. I would error towards providing example converters for decimal/char rather than having automatic behavior that may not match assumptions.

That said, I've no particular interest in any choice made here as I won't be using char in a field. More usage case info and context would be useful to this issue.

[xoofx]

That said, I've no particular interest in any choice made here as I won't be using char in a field. More usage case info and context would be useful to this issue.

Similarly to decimal, Tomlyn should probably throw a proper exception with not supported.