Add hasproperty and hasfield to Base RFC

base/exports.jl

@@ -699,7 +699,9 @@ export
     fieldnames,
     fieldcount,
     fieldtypes,
+    hasfield,
     propertynames,
+    hasproperty,
     isabstracttype,
     isbitstype,
     isprimitivetype,

base/reflection.jl

@@ -176,6 +176,14 @@ fieldnames(::Core.TypeofBottom) =
     throw(ArgumentError("The empty type does not have field names since it does not have instances."))
 fieldnames(t::Type{<:Tuple}) = ntuple(identity, fieldcount(t))
 
+"""
+    hasfield(x, name::Symbol)
+
+Returns a boolean indicating whether the object 'x' has the specified field as one of
+its own fields.
+"""
+hasfield(x, s::Symbol) = hasproperty(x, s)
+
 """
     nameof(t::DataType) -> Symbol
 
@@ -1203,3 +1211,11 @@ REPL tab completion on `x.` shows only the `private=false` properties.
 propertynames(x) = fieldnames(typeof(x))
 propertynames(m::Module) = names(m)
 propertynames(x, private) = propertynames(x) # ignore private flag by default
+
+"""
+    hasproperty(x, s::Symbol)
+
+Returns a boolean indicating whether the object `x` has the specified property as one of
+its own properties.
+"""
+hasproperty(x, s::Symbol) = s in propertynames(x)

test/reflection.jl

@@ -221,6 +221,10 @@ mutable struct TLayout
 end
 tlayout = TLayout(5,7,11)
 @test fieldnames(TLayout) == (:x, :y, :z) == Base.propertynames(tlayout)
+@test hasfield(TLayout, :y)
+@test !hasfield(TLayout, :a)
+@test hasproperty(tlayout, :x)
+@test !hasproperty(tlayout, :p)
 @test [(fieldoffset(TLayout,i), fieldname(TLayout,i), fieldtype(TLayout,i)) for i = 1:fieldcount(TLayout)] ==
     [(0, :x, Int8), (2, :y, Int16), (4, :z, Int32)]
 @test fieldnames(Complex) === (:re, :im)