add selfconstructor option

Author: jw3126

src/StructHelpers.jl

@@ -30,6 +30,10 @@ function def_getproperties(T, propertynames)
     :(StructHelpers.getproperties(o::$T) = $body)
 end
 
+function def_selfconstructor(T)
+    :($T(self::$T) = self)
+end
+
 function def_kwconstructor(T, propertynames)
     call = Expr(:call, T, Expr(:parameters, propertynames...))
     ret = :($call = $T($(propertynames...)))
@@ -40,6 +44,7 @@ const BATTERIES_DEFAULTS = (
     eq            = true ,
     hash          = true ,
     kwconstructor = false,
+    selfconstructor = true,
     kwshow        = false,
     getproperties = true ,
     constructorof = true ,
@@ -50,6 +55,7 @@ const BATTERIES_DOCSTRINGS = (
     eq            = "Define `Base.(==)` structurally.",
     hash          = "Define `Base.hash` structurally.",
     kwconstructor = "Add a keyword constructor.",
+    selfconstructor = "Add a constructor of the for `T(self::T) = self`",
     kwshow        = "Overload `Base.show` such that the names of each field are printed.",
     getproperties = "Overload `ConstructionBase.getproperties`.",
     constructorof = "Overload `ConstructionBase.constructorof`.",
@@ -160,6 +166,10 @@ macro batteries(T, kw...)
         def = def_kwconstructor(T, fieldnames)
         push!(ret.args, def)
     end
+    if nt.selfconstructor
+        def = def_selfconstructor(T)
+        push!(ret.args, def)
+    end
     return esc(ret)
 end
 
@@ -261,11 +271,13 @@ end
 const ENUM_BATTERIES_DEFAULTS = (
     string_conversion=false,
     symbol_conversion=false,
+    selfconstructor=BATTERIES_DEFAULTS.selfconstructor,
 )
 
 const ENUM_BATTERIES_DOCSTRINGS = (
     string_conversion="Add `convert(MyEnum, ::String)`, `MyEnum(::String)`, `convert(String, ::MyEnum)` and `String(::MyEnum)`",
     symbol_conversion="Add `convert(MyEnum, ::Symbol)`, `MyEnum(::Symbol)`, `convert(Symbol, ::MyEnum)` and `Symbol(::MyEnum)`",
+    selfconstructor=BATTERIES_DOCSTRINGS.selfconstructor,
 )
 
 if (keys(ENUM_BATTERIES_DEFAULTS) != keys(ENUM_BATTERIES_DOCSTRINGS))
@@ -348,6 +360,10 @@ macro enumbatteries(T, kw...)
         ex4 = :(Base.Symbol(x::$T) = StructHelpers.symbol_from_enum(x))
         push!(ret.args, ex1, ex2, ex3, ex4)
     end
+    if nt.selfconstructor
+        def = def_selfconstructor(T)
+        push!(ret.args, def)
+    end
     return esc(ret)
 end
 

test/runtests.jl

@@ -38,6 +38,11 @@ struct NoSalt end
 
 struct SErrors;a;b;c;end
 
+struct NoSelfCtor; a; end
+struct WithSelfCtor; a; end
+@batteries NoSelfCtor selfconstructor=false
+@batteries WithSelfCtor selfconstructor=true
+
 @testset "@batteries" begin
     @test SBatteries(1,2) == SBatteries(1,2)
     @test SBatteries(1,[]) == SBatteries(1,[])
@@ -80,11 +85,16 @@ struct SErrors;a;b;c;end
     @test hash(Salt1()) === hash(Salt1b())
     @test hash(Salt1()) != hash(NoSalt())
     @test hash(Salt1()) != hash(Salt2())
+
+    @test WithSelfCtor(WithSelfCtor(1)) === WithSelfCtor(1)
+    @test NoSelfCtor(NoSelfCtor(1)) != NoSelfCtor(1)
+    @test NoSelfCtor(NoSelfCtor(1)) isa NoSelfCtor
+    @test NoSelfCtor(NoSelfCtor(1)).a === NoSelfCtor(1)
 end
 
 @enum Color Red Blue Green
 
-@enumbatteries Color string_conversion = true symbol_conversion = true
+@enumbatteries Color string_conversion = true symbol_conversion = true selfconstructor = false
 
 @enum Shape Circle Square 
 @enumbatteries Shape symbol_conversion =true
@@ -95,6 +105,7 @@ end
     @test "Red" === @inferred String(Red)
     @test "Red" === @inferred convert(String, Red)
     @test_throws ArgumentError Color("Nonsense")
+    @test_throws MethodError Color(Red)
 
     @test :Red === @inferred Symbol(Red)
     @test :Red === @inferred convert(Symbol, Red)
@@ -111,6 +122,7 @@ end
     @test :Circle === @inferred convert(Symbol, Circle)
     @test Circle === @inferred Shape(:Circle)
     @test Circle === @inferred convert(Shape, :Circle)
+    @test Circle === @inferred Shape(Circle)
     @test_throws ArgumentError Shape(:Nonsense)
     res = @test_throws ArgumentError convert(Shape, :nonsense)
     @test occursin(":Circle", res.value.msg)