Support sort(keys(::Dict)) and sort(values(::Dict)) (#56978)

Part of the sorting iterables saga:
#38328
#46104
#51977
#52010
#54494

---------

Co-authored-by: Neven Sajko <[email protected]>

Author: LilithHafner

NEWS.md

@@ -25,6 +25,8 @@ New library functions
 New library features
 --------------------
 
+`sort(keys(::Dict))` and `sort(values(::Dict))` now automatically collect, they previously threw ([#56978]).
+
 Standard library changes
 ------------------------
 

base/sort.jl

@@ -1620,7 +1620,7 @@ defalg(v::AbstractArray) = DEFAULT_STABLE
 defalg(v::AbstractArray{<:Union{Number, Missing}}) = DEFAULT_UNSTABLE
 defalg(v::AbstractArray{Missing}) = DEFAULT_UNSTABLE # for method disambiguation
 defalg(v::AbstractArray{Union{}}) = DEFAULT_UNSTABLE # for method disambiguation
-defalg(v::NTuple) = DEFAULT_STABLE
+defalg(v) = DEFAULT_STABLE
 
 """
     sort!(v; alg::Base.Sort.Algorithm=Base.Sort.defalg(v), lt=isless, by=identity, rev::Bool=false, order::Base.Order.Ordering=Base.Order.Forward)
@@ -1739,13 +1739,20 @@ function sort!(v::AbstractVector{T};
 end
 
 """
-    sort(v::Union{AbstractVector, NTuple}; alg::Base.Sort.Algorithm=Base.Sort.defalg(v), lt=isless, by=identity, rev::Bool=false, order::Base.Order.Ordering=Base.Order.Forward)
+    sort(v; alg::Base.Sort.Algorithm=Base.Sort.defalg(v), lt=isless, by=identity, rev::Bool=false, order::Base.Order.Ordering=Base.Order.Forward)
+    sort(v::NTuple; kws...)::NTuple
 
 Variant of [`sort!`](@ref) that returns a sorted copy of `v` leaving `v` itself unmodified.
 
+When calling `sort` on the [`keys`](@ref) or [`values](@ref) of a dictionary, `v` is
+collected and then sorted in place.
+
 !!! compat "Julia 1.12"
     Sorting `NTuple`s requires Julia 1.12 or later.
 
+!!! compat "Julia 1.13"
+    Sorting keys sets and values iterators requires Julia 1.13 or later.
+
 # Examples
 ```jldoctest
 julia> v = [3, 1, 2];
@@ -1761,10 +1768,18 @@ julia> v
  3
  1
  2
+
+julia> sort(values(Dict('a'=>2, 'b'=>1)))
+2-element Vector{Int64}:
+ 1
+ 2
 ```
 """
 sort(v::AbstractVector; kws...) = sort!(copymutable(v); kws...)
 
+const COLLECT_ON_SORT_TYPES = Union{Base.KeySet, Base.ValueIterator}
+sort(v::COLLECT_ON_SORT_TYPES; kws...) = sort!(collect(v); kws...)
+
 function sort(x::NTuple;
               alg::Algorithm=defalg(x),
               lt=isless,

test/sorting.jl

@@ -110,6 +110,14 @@ end
     @test Base.infer_return_type(sort, Tuple{Tuple{Vararg{Int}}}) == Tuple{Vararg{Int}}
 end
 
+@testset "KeySet and ValueIterator" begin
+    x = Dict(rand() => randstring() for _ in 1:10)
+    x0 = deepcopy(x)
+    @test issorted(sort(keys(x))::Vector{Float64})
+    @test issorted(sort(values(x))::Vector{String})
+    @test x == x0
+end
+
 @testset "partialsort" begin
     @test partialsort([3,6,30,1,9],3) == 6
     @test partialsort([3,6,30,1,9],3:4) == [6,9]