improve inference of mapproperties

Author: jw3126

Project.toml

@@ -15,7 +15,7 @@ Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
 [compat]
 Compat = "3.18"
 CompositionsBase = "0.1"
-ConstructionBase = "0.1, 1.0"
+ConstructionBase = "1.2"
 MacroTools = "0.4.4, 0.5"
 Requires = "0.5, 1.0"
 StaticNumbers = "0.3"

src/optics.jl

@@ -232,21 +232,25 @@ julia> obj = (a=1, b=2);
 julia> Accessors.mapproperties(x -> x+1, obj)
 (a = 2, b = 3)
 ```
+
+# Implementation
+
+This function should not be overloaded directly. Instead both of
+* `ConstructionBase.getproperties`
+* `ConstructionBase.setproperties`
+should be overloaded.
 $EXPERIMENTAL
 """
+function mapproperties end
+
+function mapproperties(f, nt::NamedTuple)
+    map(f,nt)
+end
+
 function mapproperties(f, obj)
-    # TODO move this helper elsewhere?
-    # TODO should we use a generated function based on fieldnames?
-    pnames = propertynames(obj)
-    if isempty(pnames)
-        return obj
-    else
-        ctor = constructorof(typeof(obj))
-        new_props = map(pnames) do p
-            f(getproperty(obj, p))
-        end
-        return ctor(new_props...)
-    end
+    nt = getproperties(obj)
+    patch = mapproperties(f, nt)
+    return setproperties(obj, patch)
 end
 
 """

test/test_optics.jl

@@ -1,11 +1,48 @@
 module TestOptics
 
 using Accessors
+using Accessors: mapproperties
 using Test
+import ConstructionBase
+
+@testset "mapproperties" begin
+    res = @inferred mapproperties(x->2x, (a=1, b=2))
+    @test res === (a=2, b=4)
+    @test NamedTuple() === @inferred mapproperties(cos, NamedTuple())
+    struct S{A,B}
+        a::A
+        b::B
+    end
+    res = @inferred mapproperties(x->2x, S(1, 2.0))
+    @test res === S(2, 4.0)
+end
 
 @testset "Properties" begin
     pt = (x=1, y=2, z=3)
     @test (x=0, y=1, z=2) === @set pt |> Properties() -= 1
+    @inferred modify(x->x-1, pt, Properties())
+
+    # custom struct
+    struct Point{X,Y,Z}
+        x::X; y::Y; z::Z
+    end
+    pt = Point(1f0, 2e0, 3)
+    pt2 = @inferred modify(x->2x, pt, Properties())
+    @test pt2 === Point(2f0, 4e0, 6)
+
+    # overloading
+    struct AB
+        a::Int
+        b::Int
+        _checksum::Int
+        AB(a,b) = new(a,b,a+b)
+    end
+
+    ConstructionBase.getproperties(o::AB) = (a=o.a, b=o.b)
+    ConstructionBase.setproperties(o::AB, patch::NamedTuple) = AB(patch.a, patch.b)
+    ab = AB(1,2)
+    ab2 = @inferred mapproperties(x -> 2x, ab)
+    @test ab2 === AB(2,4)
 end
 
 @testset "Elements" begin