Support sorting iterators (#46104)

* widen sort's type signature

* throw on AbstractString

* Throw on infinite iterator

* make sort(::NTuple) return a tuple (use vector internally for sorting for large tuples)

Author: LilithHafner

base/sort.jl

@@ -5,7 +5,8 @@ module Sort
 using Base.Order
 
 using Base: copymutable, midpoint, require_one_based_indexing, uinttype,
-    sub_with_overflow, add_with_overflow, OneTo, BitSigned, BitIntegerType, top_set_bit
+    sub_with_overflow, add_with_overflow, OneTo, BitSigned, BitIntegerType, top_set_bit,
+    IteratorSize, HasShape, IsInfinite, tail
 
 import Base:
     sort,
@@ -1383,6 +1384,11 @@ end
 
 Variant of [`sort!`](@ref) that returns a sorted copy of `v` leaving `v` itself unmodified.
 
+Uses `Base.copymutable` to support immutable collections and iterables.
+
+!!! compat "Julia 1.10"
+    `sort` of arbitrary iterables requires at least Julia 1.10.
+
 # Examples
 ```jldoctest
 julia> v = [3, 1, 2];
@@ -1400,7 +1406,39 @@ julia> v
  2
 ```
 """
-sort(v::AbstractVector; kws...) = sort!(copymutable(v); kws...)
+function sort(v; kws...)
+    size = IteratorSize(v)
+    size == HasShape{0}() && throw(ArgumentError("$v cannot be sorted"))
+    size == IsInfinite() && throw(ArgumentError("infinite iterator $v cannot be sorted"))
+    sort!(copymutable(v); kws...)
+end
+sort(v::AbstractVector; kws...) = sort!(copymutable(v); kws...) # for method disambiguation
+sort(::AbstractString; kws...) =
+    throw(ArgumentError("sort(::AbstractString) is not supported"))
+sort(::Tuple; kws...) =
+    throw(ArgumentError("sort(::Tuple) is only supported for NTuples"))
+
+function sort(x::NTuple{N}; lt::Function=isless, by::Function=identity,
+              rev::Union{Bool,Nothing}=nothing, order::Ordering=Forward) where N
+    o = ord(lt,by,rev,order)
+    if N > 9
+        v = sort!(copymutable(x), DEFAULT_STABLE, o)
+        tuple((v[i] for i in 1:N)...)
+    else
+        _sort(x, o)
+    end
+end
+_sort(x::Union{NTuple{0}, NTuple{1}}, o::Ordering) = x
+function _sort(x::NTuple, o::Ordering)
+    a, b = Base.IteratorsMD.split(x, Val(length(x)>>1))
+    merge(_sort(a, o), _sort(b, o), o)
+end
+merge(x::NTuple, y::NTuple{0}, o::Ordering) = x
+merge(x::NTuple{0}, y::NTuple, o::Ordering) = y
+merge(x::NTuple{0}, y::NTuple{0}, o::Ordering) = x # Method ambiguity
+merge(x::NTuple, y::NTuple, o::Ordering) =
+    (lt(o, y[1], x[1]) ? (y[1], merge(x, tail(y), o)...) : (x[1], merge(tail(x), y, o)...))
+
 
 ## partialsortperm: the permutation to sort the first k elements of an array ##
 

test/sorting.jl

@@ -88,6 +88,20 @@ end
         vcat(2000, (x:x+99 for x in 1900:-100:100)..., 1:99)
 end
 
+function tuple_sort_test(x)
+    @test issorted(sort(x))
+    length(x) > 9 && return # length > 9 uses a vector fallback
+    @test 0 == @allocated sort(x)
+end
+@testset "sort(::NTuple)" begin
+    @test sort((9,8,3,3,6,2,0,8)) == (0,2,3,3,6,8,8,9)
+    @test sort((9,8,3,3,6,2,0,8), by=x->x÷3) == (2,0,3,3,8,6,8,9)
+    for i in 1:40
+        tuple_sort_test(tuple(rand(i)...))
+    end
+    @test_throws ArgumentError sort((1,2,3.0))
+end
+
 @testset "partialsort" begin
     @test partialsort([3,6,30,1,9],3) == 6
     @test partialsort([3,6,30,1,9],3:4) == [6,9]
@@ -530,6 +544,23 @@ end
     @test isequal(a, [8,6,7,NaN,5,3,0,9])
 end
 
+@testset "sort!(iterable)" begin
+    gen = (x % 7 + 0.1x for x in 1:50)
+    @test sort(gen) == sort!(collect(gen))
+    gen = (x % 7 + 0.1y for x in 1:10, y in 1:5)
+    @test sort(gen; dims=1) == sort!(collect(gen); dims=1)
+    @test sort(gen; dims=2) == sort!(collect(gen); dims=2)
+
+    @test_throws ArgumentError("dimension out of range") sort(gen; dims=3)
+
+    @test_throws UndefKeywordError(:dims) sort(gen)
+    @test_throws UndefKeywordError(:dims) sort(collect(gen))
+    @test_throws UndefKeywordError(:dims) sort!(collect(gen))
+
+    @test_throws ArgumentError sort("string")
+    @test_throws ArgumentError("1 cannot be sorted") sort(1)
+end
+
 @testset "sort!(::AbstractVector{<:Integer}) with short int range" begin
     a = view([9:-1:0;], :)::SubArray
     sort!(a)