From fc1362c743a3e5a5fccb1aaaea9d924386dd9397 Mon Sep 17 00:00:00 2001
From: stanislav <sgryumov@bhft.com>
Date: Wed, 12 Feb 2025 20:03:05 +0500
Subject: [PATCH] Add dynamic deserialization of AbstractTypes

---
 Project.toml    |  1 +
 src/De/De.jl    | 38 +++++++++++++-------------------------
 src/De/Deser.jl | 16 +++++++++++++++-
 src/Serde.jl    |  2 ++
 4 files changed, 31 insertions(+), 26 deletions(-)

diff --git a/Project.toml b/Project.toml
index 188d31ae..bdf9f376 100644
--- a/Project.toml
+++ b/Project.toml
@@ -6,6 +6,7 @@ version = "3.5.0"
 CSV = "336ed68f-0bac-5ca0-87d4-7b16caf5d00b"
 Dates = "ade2ca70-3891-5945-98fb-dc099432e06a"
 EzXML = "8f5d6c58-4d21-5cfd-889c-e3ad7ee6a615"
+InteractiveUtils = "b77e0a4c-d291-57a0-90e8-8db25a27a240"
 JSON = "682c06a0-de6a-54ab-a142-c8b1cf79cde6"
 TOML = "fa267f1f-6049-4f14-aa54-33bafae1ed76"
 UUIDs = "cf7118a7-6976-5b1a-9a39-7adc72f591a4"
diff --git a/src/De/De.jl b/src/De/De.jl
index a310cf56..a41a6603 100644
--- a/src/De/De.jl
+++ b/src/De/De.jl
@@ -13,12 +13,20 @@ function Base.show(io::IO, e::ParamError)
     )
 end
 
-struct TagError <: DeserError
-    tag::Any
+struct MissingKeyError <: DeserError
+    key::Any
+end
+
+function Base.show(io::IO, e::MissingKeyError)
+    return print(io, "KeyError: required key '$(e.key)' is missing or invalid.")
 end
 
-function Base.show(io::IO, e::TagError)
-    return print(io, "TagError: tag for method '$(e.tag)' is not declared")
+struct UndefKeyError <: DeserError
+    type::Type
+end
+
+function Base.show(io::IO, e::UndefKeyError)
+    print(io, "UndefKeyError: define `subtype_key(::Type{$(e.type)})` to specify the subtype field.")
 end
 
 struct WrongType <: DeserError
@@ -38,26 +46,6 @@ end
 
 include("Deser.jl")
 
-function tag(::Type{T}, ::Val{x}) where {T,x}
-    return throw(TagError(x))
-end
-
-tag(::Type{T}, ::Nothing) where {T} = T
-
-(tag_key(::Type)::Nothing) = nothing
-(tag_val(::Type{T}, ::Nothing, v)::Nothing) where {T} = nothing
-
-function tag_val(::Type{T}, k, v) where {T}
-    try
-        Val(Symbol(v[k]))
-    catch
-        throw(ParamError(k))
-    end
-end
-
-deser_type(::Type{T}, x) where {T} = tag(T, tag_val(T, tag_key(T), x))
-deser_value(::Type{T}, x) where {T} = x
-
 """
     Serde.to_deser(::Type{T}, x) -> T
 
@@ -84,7 +72,7 @@ julia> Serde.to_deser(Person, person_data)
 Person("Michael", 25, Info(12, 2500))
 ```
 """
-to_deser(::Type{T}, x) where {T} = deser(deser_type(T, x), deser_value(T, x))
+to_deser(::Type{T}, x) where {T} = deser(T, x)
 
 to_deser(::Type{Nothing}, x) = nothing
 to_deser(::Type{Missing}, x) = missing
diff --git a/src/De/Deser.jl b/src/De/Deser.jl
index ee6f198e..260c3f11 100644
--- a/src/De/Deser.jl
+++ b/src/De/Deser.jl
@@ -14,6 +14,7 @@ For more details:
 """
 abstract type ClassType end
 
+struct AbstractType <: ClassType end
 struct CustomType <: ClassType end
 struct NullType <: ClassType end
 struct PrimitiveType <: ClassType end
@@ -214,7 +215,7 @@ See also [`Serde.nulltype`](@ref), [`Serde.default_value`](@ref), [`Serde.isempt
 
 ## Examples:
 
-Let's make a custom type `Computer` with the following fields and constructor. 
+Let's make a custom type `Computer` with the following fields and constructor.
 ```julia
 struct Computer
     cpu::String
@@ -411,6 +412,19 @@ end
     end
 end
 
+subtype_key(::Type{T}) where {T<:Any} = nothing
+
+function deser(::AbstractType, ::Type{T}, data::AbstractDict{K,D})::T where {T,K,D}
+    field = subtype_key(T)
+    field === nothing && throw(UndefKeyError(T))
+    for sub in subtypes(T)
+        if nameof(sub) == Symbol(data[K(field)])
+            return deser(CustomType(), sub, data)
+        end
+    end
+    throw(MissingKeyError(field))
+end
+
 function deser(::CustomType, ::Type{T}, data::AbstractVector{A})::T where {T<:Any,A<:Any}
     veclen = fieldcount(T)
     target = Vector{Any}(undef, veclen)
diff --git a/src/Serde.jl b/src/Serde.jl
index f8ac0b52..532a8965 100644
--- a/src/Serde.jl
+++ b/src/Serde.jl
@@ -1,5 +1,7 @@
 module Serde
 
+using InteractiveUtils
+
 function deser end
 function parse_value end