Parsing JSON ignores StructUtils methods for custom JSONStyle

[curtd]

JSON v1.5.1 internally enforces the use of JSONReadStyle, which doesn't forward the StructUtils API to the corresponding methods defined for custom JSONStyle, breaking previous deserialization behaviour from JSON 1.5.0.

Minimal reproducing example

       import JSON, StructUtils

       @kwdef struct A 
            vals::Dict{String, Int} = Dict{String, Int}()
       end
       Base.keytype(::A) = String
       Base.valtype(::A) = Int
       StructUtils.addkeyval!(a::A, k, v) = StructUtils.addkeyval!(a.vals, k, v)
       struct CustomJSONStyle <: JSON.JSONStyle end 
       StructUtils.dictlike(::CustomJSONStyle, ::Type{A}) = true 

       str = """{"a": 1, "b": 2 }"""

On JSON 1.5.0

julia> JSON.parse(str, A; style=CustomJSONStyle())
A(Dict("b" => 2, "a" => 1))

On JSON 1.5.1

julia> JSON.parse(str, A; style=CustomJSONStyle())
ERROR: TypeError: in typeassert, expected Dict{String, Int64}, got a value of type Nothing
Stacktrace:
 [1] macro expansion
   @ ~/.julia/packages/StructUtils/RFX5w/src/StructUtils.jl:-1 [inlined]
 [2] _construct
   @ ~/.julia/packages/StructUtils/RFX5w/src/StructUtils.jl:1154 [inlined]
 [3] makestruct
   @ ~/.julia/packages/StructUtils/RFX5w/src/StructUtils.jl:1176 [inlined]
 [4] make
   @ ~/.julia/packages/StructUtils/RFX5w/src/StructUtils.jl:942 [inlined]
 [5] _parse
   @ ~/.julia/packages/JSON/5986W/src/parse.jl:223 [inlined]
 [6] parse(x::JSON.LazyValue{…}, ::Type{…}; dicttype::Type{…}, null::Nothing, style::CustomJSONStyle, unknown_fields::Symbol)
   @ JSON ~/.julia/packages/JSON/5986W/src/parse.jl:217
 [7] parse
   @ ~/.julia/packages/JSON/5986W/src/parse.jl:217 [inlined]
 [8] #parse#52
   @ ~/.julia/packages/JSON/5986W/src/parse.jl:207 [inlined]
 [9] top-level scope
   @ REPL[12]:1
Some type information was truncated. Use `show(err)` to see complete types.

[Affie]

I think I ran into the same issue upgrading from v1.5.0

[Affie]

Hi @quinnj,
Thanks for fixing this but it looks like it was only partially fixed. Is #454 maybe missing something like StructUtils.structlike(st::JSONReadStyle, ::Type{T}) where {T} = StructUtils.structlike(st.style, T)?

Here is a minimum reproducer that works in v1.5.0.

using Test, JSON, StructUtils

# Using Base.RefValue{Int} as an foreign type example, but any place where we cannot use `@nonstruct` is applicable.

struct MyStyle <: JSON.JSONStyle end
StructUtils.structlike(::MyStyle, ::Type{Base.RefValue{Int}}) = false
StructUtils.lower(::MyStyle, x::Base.RefValue{Int}) = x[]
StructUtils.lift(::MyStyle, ::Type{Base.RefValue{Int}}, x::Integer) = Ref{Int}(x), nothing

# Round-trip as a field
jstr = JSON.json(Ref{Int}(1); style=MyStyle())
@test jstr == "1"

parsed = JSON.parse(jstr, Base.RefValue{Int}; style=MyStyle())
@test parsed[] == 1

I get this error in v1.6.0

ERROR: ArgumentError: applyeach not applicable for `JSON.LazyValue{String}` with JSON type = `JSONTypes.NUMBER`
Stacktrace:
 [1] applyeach
   @ ~/.julia/packages/JSON/e9wDJ/src/lazy.jl:188 [inlined]
 [2] makestruct
   @ ~/.julia/packages/StructUtils/rXMKH/src/StructUtils.jl:1203 [inlined]
 [3] make
   @ ~/.julia/packages/StructUtils/rXMKH/src/StructUtils.jl:968 [inlined]
 [4] _parse
   @ ~/.julia/packages/JSON/e9wDJ/src/parse.jl:230 [inlined]
 [5] parse(x::JSON.LazyValue{…}, ::Type{…}; dicttype::Type{…}, null::Nothing, style::MyStyle, unknown_fields::Symbol)
   @ JSON ~/.julia/packages/JSON/e9wDJ/src/parse.jl:224
 [6] parse
   @ ~/.julia/packages/JSON/e9wDJ/src/parse.jl:224 [inlined]
 [7] #parse#52
   @ ~/.julia/packages/JSON/e9wDJ/src/parse.jl:214 [inlined]
 [8] top-level scope
   @ REPL[8]:1
Some type information was truncated. Use `show(err)` to see complete types.