Constructing immutable structs from keyword constructors

[Eric Forgy]

I bumped into this today and think it would also help with #69

julia> Base.@kwdef struct Test
           t1::String=""
           t2::String=""
       end
Test

julia> StructType(::Type{Test}) = Struct()
StructType

julia> JSON3.read("""{"t1":"Hello","t2":"world"}""",Test)
Test("Hello", "world")

julia> JSON3.read("""{"t1":"Hello"}""",Test)
ERROR: ArgumentError: invalid JSON at byte position 16 while parsing type String: UnexpectedEOF
{"t1":"Hello"}

julia> JSON3.read("""{"t2":"Hello","t1":"world"}""",Test)
Test("Hello", "world")

The last one (related to #69 ) threw me 😅

It would be awesome if JSON3 could somehow try to use a keyword constructor so

julia> JSON3.read("""{"t1":"Hello"}""",Test)

maps to

Test(t1="Hello")

[Eric Forgy]

Just an idea, but maybe in addition to Struct() and Mutable() there could be a Keyword() 🤔

[Jacob Quinn]

This would be a better issue for StructTypes; if there's still interest, let's open an issue up over htere.