adding sort=true keyword to readdir() according to #24626

NEWS.md

@@ -30,6 +30,7 @@ New library functions
 * The `tempname` function now takes an optional `parent::AbstractString` argument to give it a directory in which to attempt to produce a temporary path name ([#33090]).
 * The `tempname` function now takes a `cleanup::Bool` keyword argument defaulting to `true`, which causes the process to try to ensure that any file or directory at the path returned by `tempname` is deleted upon process exit ([#33090]).
 * The `readdir` function now takes a `join::Bool` keyword argument defaulting to `false`, which when set causes `readdir` to join its directory argument with each listed name ([#33113]).
+* `readdir` output is now guaranteed to be sorted. The `sort` keyword allows opting out of sorting to get names in OS-native order ([#33542]).
 * The new `only(x)` function returns the one-and-only element of a collection `x`, and throws an `ArgumentError` if `x` contains zero or multiple elements. ([#33129])
 * `takewhile` and `dropwhile` have been added to the Iterators submodule ([#33437]).
 

base/file.jl

@@ -678,16 +678,23 @@ struct uv_dirent_t
 end
 
 """
-    readdir(dir::AbstractString=pwd(); join::Bool=false) -> Vector{String}
+    readdir(dir::AbstractString=pwd();
+        join::Bool = false,
+        sort::Bool = true,
+    ) -> Vector{String}
 
 Return the names in the directory `dir` or the current working directory if not
 given. When `join` is false, `readdir` returns just the names in the directory
 as is; when `join` is true, it returns `joinpath(dir, name)` for each `name` so
 that the returned strings are full paths. If you want to get absolute paths
 back, call `readdir` with an absolute directory path and `join` set to true.
 
+By default, `readdir` sorts the list of names it returns. If you want to skip
+sorting the names and get them in the order that the file system lists them,
+you can use `readir(dir, sort=false)` to opt out of sorting.
+
 !!! compat "Julia 1.4"
-    The `join` keyword argument requires at least Julia 1.4.
+    The `join` and `sort` keyword arguments require at least Julia 1.4.
 
 # Examples
 ```julia-repl
@@ -744,7 +751,7 @@ julia> readdir(abspath("base"), join=true)
  "/home/JuliaUser/dev/julia/base/weakkeydict.jl"
 ```
 """
-function readdir(dir::AbstractString; join::Bool=false)
+function readdir(dir::AbstractString; join::Bool=false, sort::Bool=true)
     # Allocate space for uv_fs_t struct
     uv_readdir_req = zeros(UInt8, ccall(:jl_sizeof_uv_fs_t, Int32, ()))
 
@@ -764,9 +771,13 @@ function readdir(dir::AbstractString; join::Bool=false)
     # Clean up the request string
     ccall(:uv_fs_req_cleanup, Cvoid, (Ptr{UInt8},), uv_readdir_req)
 
+    # sort entries unless opted out
+    sort && sort!(entries)
+
     return entries
 end
-readdir(; join::Bool=false) = readdir(join ? pwd() : ".", join=join)
+readdir(; join::Bool=false, sort::Bool=true) =
+    readdir(join ? pwd() : ".", join=join, sort=sort)
 
 """
     walkdir(dir; topdown=true, follow_symlinks=false, onerror=throw)

test/file.jl

@@ -1277,6 +1277,20 @@ cd(dirwalk) do
 end
 rm(dirwalk, recursive=true)
 
+###################
+#     readdir     #
+###################
+@testset "readdir is sorted" begin
+    mktempdir() do dir
+        cd(dir) do
+            for k in 1:10
+                touch(randstring())
+            end
+            @test issorted(readdir())
+        end
+    end
+end
+
 ############
 # Clean up #
 ############