Adding sort=true keyword to readdir()

NEWS.md

@@ -383,6 +383,9 @@ Library improvements
     This supersedes the old behavior of reinterpret on Arrays. As a result, reinterpreting
     arrays with different alignment requirements (removed in 0.6) is once again allowed ([#23750]).
 
+  * `readdir()` output is now guaranteed to be sorted on any OS. A new `sort` keyword argument can
+    be used to disable explicit sorting ([#24626]).
+
 Compiler/Runtime improvements
 -----------------------------
 

base/file.jl

@@ -401,11 +401,12 @@ struct uv_dirent_t
 end
 
 """
-    readdir(dir::AbstractString=".") -> Vector{String}
+    readdir(dir::AbstractString="."; sort::Bool=true) -> Vector{String}
 
 Returns the files and directories in the directory `dir` (or the current working directory if not given).
+If `sort=false`, the resulting list won't necessarily be sorted, but performance may improve slightly.
 """
-function readdir(path::AbstractString)
+function readdir(path::AbstractString; sort::Bool=true)
     # Allocate space for uv_fs_t struct
     uv_readdir_req = zeros(UInt8, ccall(:jl_sizeof_uv_fs_t, Int32, ()))
 
@@ -425,6 +426,9 @@ function readdir(path::AbstractString)
     # Clean up the request string
     ccall(:jl_uv_fs_req_cleanup, Void, (Ptr{UInt8},), uv_readdir_req)
 
+    # sort entries if not requested otherwise
+    sort && sort!(entries)
+
     return entries
 end
 

test/file.jl

@@ -959,6 +959,19 @@ cd(dirwalk) do
 end
 rm(dirwalk, recursive=true)
 
+###################
+#     readdir     #
+###################
+
+mktempdir() do path
+    cd(path) do
+        for k in 1:10
+            touch(randstring())
+        end
+        @test issorted(readdir())
+    end
+end
+
 ############
 # Clean up #
 ############