Deprecate DevNull, STDIN, STDOUT, and STDERR to lowercase

DISTRIBUTING.md

@@ -375,7 +375,7 @@ for result in eachrow(results)
 end
 ```
 
-This will write color-coded lines to STDOUT.
+This will write color-coded lines to `stdout`.
 All lines in red must be investigated as they signify potential breakages caused by the
 backport version.
 Lines in yellow should be looked into since it means a package ran on one version but

NEWS.md

@@ -1072,6 +1072,9 @@ Deprecated or removed
   * The fallback method `^(x, p::Integer)` is deprecated. If your type relied on this definition,
     add a method such as `^(x::MyType, p::Integer) = Base.power_by_squaring(x, p)` ([#23332]).
 
+  * `DevNull`, `STDIN`, `STDOUT`, and `STDERR` have been renamed to `devnull`, `stdin`, `stdout`,
+    and `stderr`, respectively ([#25786]).
+
   * `wait` and `fetch` on `Task` now resemble the interface of `Future`
 
 Command-line option changes
@@ -1369,4 +1372,4 @@ Command-line option changes
 [#25990]: https://github.com/JuliaLang/julia/issues/25990
 [#25998]: https://github.com/JuliaLang/julia/issues/25998
 [#26009]: https://github.com/JuliaLang/julia/issues/26009
-[#26071]: https://github.com/JuliaLang/julia/issues/26071
+[#26071]: https://github.com/JuliaLang/julia/issues/26071

base/boot.jl

@@ -430,8 +430,8 @@ atdoc!(λ) = global atdoc = λ
 abstract type IO end
 struct CoreSTDOUT <: IO end
 struct CoreSTDERR <: IO end
-const STDOUT = CoreSTDOUT()
-const STDERR = CoreSTDERR()
+const stdout = CoreSTDOUT()
+const stderr = CoreSTDERR()
 io_pointer(::CoreSTDOUT) = Intrinsics.pointerref(Intrinsics.cglobal(:jl_uv_stdout, Ptr{Cvoid}), 1, 1)
 io_pointer(::CoreSTDERR) = Intrinsics.pointerref(Intrinsics.cglobal(:jl_uv_stderr, Ptr{Cvoid}), 1, 1)
 
@@ -455,9 +455,9 @@ print(io::IO, @nospecialize(x), @nospecialize a...) = (print(io, x); print(io, a
 println(io::IO) = (write(io, 0x0a); nothing) # 0x0a = '\n'
 println(io::IO, @nospecialize x...) = (print(io, x...); println(io))
 
-show(@nospecialize a) = show(STDOUT, a)
-print(@nospecialize a...) = print(STDOUT, a...)
-println(@nospecialize a...) = println(STDOUT, a...)
+show(@nospecialize a) = show(stdout, a)
+print(@nospecialize a...) = print(stdout, a...)
+println(@nospecialize a...) = println(stdout, a...)
 
 struct GeneratedFunctionStub
     gen

base/client.jl

@@ -165,7 +165,7 @@ function display_error(io::IO, er, bt)
     showerror(IOContext(io, :limit => true), er, bt)
     println(io)
 end
-display_error(er, bt) = display_error(STDERR, er, bt)
+display_error(er, bt) = display_error(stderr, er, bt)
 display_error(er) = display_error(er, [])
 
 function eval_user_input(@nospecialize(ast), show_value::Bool)
@@ -189,7 +189,7 @@ function eval_user_input(@nospecialize(ast), show_value::Bool)
                     try
                         invokelatest(display, value)
                     catch err
-                        println(STDERR, "Evaluation succeeded, but an error occurred while showing value of type ", typeof(value), ":")
+                        println(stderr, "Evaluation succeeded, but an error occurred while showing value of type ", typeof(value), ":")
                         rethrow(err)
                     end
                     println()
@@ -198,17 +198,17 @@ function eval_user_input(@nospecialize(ast), show_value::Bool)
             break
         catch err
             if errcount > 0
-                println(STDERR, "SYSTEM: show(lasterr) caused an error")
+                println(stderr, "SYSTEM: show(lasterr) caused an error")
             end
             errcount, lasterr = errcount+1, err
             if errcount > 2
-                println(STDERR, "WARNING: it is likely that something important is broken, and Julia will not be able to continue normally")
+                println(stderr, "WARNING: it is likely that something important is broken, and Julia will not be able to continue normally")
                 break
             end
             bt = catch_backtrace()
         end
     end
-    isa(STDIN, TTY) && println()
+    isa(stdin, TTY) && println()
     nothing
 end
 
@@ -333,7 +333,7 @@ function exec_options(opts)
     end
     repl |= is_interactive
     if repl
-        interactiveinput = isa(STDIN, TTY)
+        interactiveinput = isa(stdin, TTY)
         if interactiveinput
             global is_interactive = true
             banner = (opts.banner != 0) # --banner!=no
@@ -374,8 +374,8 @@ function __atreplinit(repl)
         try
             f(repl)
         catch err
-            showerror(STDERR, err)
-            println(STDERR)
+            showerror(stderr, err)
+            println(stderr)
         end
     end
 end
@@ -390,7 +390,7 @@ function run_main_repl(interactive::Bool, quiet::Bool, banner::Bool, history_fil
     if interactive && isassigned(REPL_MODULE_REF)
         invokelatest(REPL_MODULE_REF[]) do REPL
             term_env = get(ENV, "TERM", @static Sys.iswindows() ? "" : "dumb")
-            term = REPL.Terminals.TTYTerminal(term_env, STDIN, STDOUT, STDERR)
+            term = REPL.Terminals.TTYTerminal(term_env, stdin, stdout, stderr)
             color_set || (global have_color = REPL.Terminals.hascolor(term))
             banner && REPL.banner(term, term)
             if term.term_type == "dumb"
@@ -412,7 +412,7 @@ function run_main_repl(interactive::Bool, quiet::Bool, banner::Bool, history_fil
             @warn "REPL provider not available: using basic fallback"
         end
         banner && Base.banner()
-        let input = STDIN
+        let input = stdin
             if isa(input, File) || isa(input, IOStream)
                 # for files, we can slurp in the whole thing at once
                 ex = parse_input_line(read(input, String))
@@ -430,7 +430,7 @@ function run_main_repl(interactive::Bool, quiet::Bool, banner::Bool, history_fil
                 while isopen(input) || !eof(input)
                     if interactive
                         print("julia> ")
-                        flush(STDOUT)
+                        flush(stdout)
                     end
                     eval_user_input(parse_input_line(input), true)
                 end

base/clipboard.jl

@@ -4,7 +4,7 @@
 
 if Sys.isapple()
     function clipboard(x)
-        open(pipeline(`pbcopy`, stderr=STDERR), "w") do io
+        open(pipeline(`pbcopy`, stderr=stderr), "w") do io
             print(io, x)
         end
     end
@@ -28,7 +28,7 @@ elseif Sys.islinux() || Sys.KERNEL === :FreeBSD
         global _clipboardcmd
         _clipboardcmd !== nothing && return _clipboardcmd
         for cmd in (:xclip, :xsel)
-            success(pipeline(`which $cmd`, DevNull)) && return _clipboardcmd = cmd
+            success(pipeline(`which $cmd`, devnull)) && return _clipboardcmd = cmd
         end
         pkgs = @static if Sys.islinux()
             "xsel or xclip"
@@ -43,7 +43,7 @@ elseif Sys.islinux() || Sys.KERNEL === :FreeBSD
         if cmd === nothing
             error("unexpected clipboard command: $c")
         end
-        open(pipeline(cmd, stderr=STDERR), "w") do io
+        open(pipeline(cmd, stderr=stderr), "w") do io
             print(io, x)
         end
     end
@@ -53,7 +53,7 @@ elseif Sys.islinux() || Sys.KERNEL === :FreeBSD
         if cmd === nothing
             error("unexpected clipboard command: $c")
         end
-        read(pipeline(cmd, stderr=STDERR), String)
+        read(pipeline(cmd, stderr=stderr), String)
     end
 
 elseif Sys.iswindows()

base/compiler/bootstrap.jl

@@ -15,7 +15,7 @@ let fs = Any[typeinf_ext, typeinf, typeinf_edge, pure_eval_call],
             x = T_IFUNC[i]
             push!(fs, x[3])
         else
-            println(STDERR, "WARNING: tfunc missing for ", reinterpret(IntrinsicFunction, Int32(i)))
+            println(stderr, "WARNING: tfunc missing for ", reinterpret(IntrinsicFunction, Int32(i)))
         end
     end
     for f in fs

base/compiler/compiler.jl

@@ -4,7 +4,7 @@ getfield(getfield(Main, :Core), :eval)(getfield(Main, :Core), :(baremodule Compi
 
 using Core.Intrinsics, Core.IR
 
-import Core: print, println, show, write, unsafe_write, STDOUT, STDERR,
+import Core: print, println, show, write, unsafe_write, stdout, stderr,
              _apply, svec, apply_type, Builtin, IntrinsicFunction, MethodInstance
 
 const getproperty = getfield

base/compiler/optimize.jl

@@ -3733,7 +3733,7 @@ macro check_ast(ctx, ex)
             println("Code:")
             println(ctx.sv.src)
             println("Value Info Map:")
-            show_info(STDOUT, ctx.infomap, ctx)
+            show_info(stdout, ctx.infomap, ctx)
             ccall(:abort, Union{}, ())
         end
     end

base/compiler/validation.jl

@@ -59,10 +59,10 @@ function validate_code_in_debug_mode(linfo::MethodInstance, src::CodeInfo, kind:
         if !isempty(errors)
             for e in errors
                 if linfo.def isa Method
-                    println(STDERR, "WARNING: Encountered invalid ", kind, " code for method ",
+                    println(stderr, "WARNING: Encountered invalid ", kind, " code for method ",
                             linfo.def, ": ", e)
                 else
-                    println(STDERR, "WARNING: Encountered invalid ", kind, " code for top level expression in ",
+                    println(stderr, "WARNING: Encountered invalid ", kind, " code for top level expression in ",
                             linfo.def, ": ", e)
                 end
             end

base/coreio.jl

@@ -1,11 +1,11 @@
 # This file is a part of Julia. License is MIT: https://julialang.org/license
 
-print(xs...)   = print(STDOUT::IO, xs...)
-println(xs...) = println(STDOUT::IO, xs...)
+print(xs...)   = print(stdout::IO, xs...)
+println(xs...) = println(stdout::IO, xs...)
 println(io::IO) = print(io, '\n')
 
 struct DevNullStream <: IO end
-const DevNull = DevNullStream()
+const devnull = DevNullStream()
 isreadable(::DevNullStream) = false
 iswritable(::DevNullStream) = true
 isopen(::DevNullStream) = true
@@ -26,6 +26,6 @@ let CoreIO = Union{Core.CoreSTDOUT, Core.CoreSTDERR}
     unsafe_write(io::CoreIO, x::Ptr{UInt8}, nb::UInt) = Core.unsafe_write(io, x, nb)
 end
 
-STDIN = DevNull
-STDOUT = Core.STDOUT
-STDERR = Core.STDERR
+stdin = devnull
+stdout = Core.stdout
+stderr = Core.stderr

base/deprecated.jl

@@ -122,12 +122,12 @@ end
 
 deprecate(m::Module, s::Symbol, flag=1) = ccall(:jl_deprecate_binding, Cvoid, (Any, Any, Cint), m, s, flag)
 
-macro deprecate_binding(old, new, export_old=true, dep_message=nothing)
+macro deprecate_binding(old, new, export_old=true, dep_message=nothing, constant=true)
     dep_message == nothing && (dep_message = ", use $new instead.")
     return Expr(:toplevel,
          export_old ? Expr(:export, esc(old)) : nothing,
          Expr(:const, Expr(:(=), esc(Symbol(string("_dep_message_",old))), esc(dep_message))),
-         Expr(:const, Expr(:(=), esc(old), esc(new))),
+         constant ? Expr(:const, Expr(:(=), esc(old), esc(new))) : Expr(:(=), esc(old), esc(new)),
          Expr(:call, :deprecate, __module__, Expr(:quote, old)))
 end
 
@@ -961,14 +961,14 @@ function info(io::IO, msg...; prefix="INFO: ")
     print(io, String(take!(buf)))
     return
 end
-info(msg...; prefix="INFO: ") = info(STDERR, msg..., prefix=prefix)
+info(msg...; prefix="INFO: ") = info(stderr, msg..., prefix=prefix)
 
 # print a warning only once
 
 const have_warned = Set()
 
 warn_once(io::IO, msg...) = warn(io, msg..., once=true)
-warn_once(msg...) = warn(STDERR, msg..., once=true)
+warn_once(msg...) = warn(stderr, msg..., once=true)
 
 """
     warn([io, ] msg..., [prefix="WARNING: ", once=false, key=nothing, bt=nothing, filename=nothing, lineno::Int=0])
@@ -1018,19 +1018,19 @@ julia> warn("Beep Beep")
 WARNING: Beep Beep
 ```
 """
-warn(msg...; kw...) = warn(STDERR, msg...; kw...)
+warn(msg...; kw...) = warn(stderr, msg...; kw...)
 
 warn(io::IO, err::Exception; prefix="ERROR: ", kw...) =
     warn(io, sprint(showerror, err), prefix=prefix; kw...)
 
 warn(err::Exception; prefix="ERROR: ", kw...) =
-    warn(STDERR, err, prefix=prefix; kw...)
+    warn(stderr, err, prefix=prefix; kw...)
 
 info(io::IO, err::Exception; prefix="ERROR: ", kw...) =
     info(io, sprint(showerror, err), prefix=prefix; kw...)
 
 info(err::Exception; prefix="ERROR: ", kw...) =
-    info(STDERR, err, prefix=prefix; kw...)
+    info(stderr, err, prefix=prefix; kw...)
 
 # issue #25082
 @deprecate_binding Void Nothing
@@ -1436,6 +1436,13 @@ function slicedim(A::AbstractVector, d::Integer, i::Number)
     end
 end
 
+# Issue #25786
+@deprecate_binding DevNull devnull
+# TODO: When these are removed, also remove the uppercase variants in libuv.jl and stream.jl
+@deprecate_binding STDIN stdin true nothing false
+@deprecate_binding STDOUT stdout true nothing false
+@deprecate_binding STDERR stderr true nothing false
+
 # PR 25062
 @deprecate(link_pipe(pipe; julia_only_read = true, julia_only_write = true),
            link_pipe!(pipe, reader_supports_async = julia_only_read, writer_supports_async = julia_only_write),

base/docs/basedocs.jl

@@ -789,16 +789,16 @@ A variable referring to the last computed value, automatically set at the intera
 kw"ans"
 
 """
-    DevNull
+    devnull
 
 Used in a stream redirect to discard all data written to it. Essentially equivalent to
 /dev/null on Unix or NUL on Windows. Usage:
 
 ```julia
-run(pipeline(`cat test.txt`, DevNull))
+run(pipeline(`cat test.txt`, devnull))
 ```
 """
-DevNull
+devnull
 
 # doc strings for code in boot.jl and built-ins
 

base/download.jl

@@ -19,7 +19,7 @@ else
         global downloadcmd
         if downloadcmd === nothing
             for checkcmd in (:curl, :wget, :fetch)
-                if success(pipeline(`which $checkcmd`, DevNull))
+                if success(pipeline(`which $checkcmd`, devnull))
                     downloadcmd = checkcmd
                     break
                 end

base/errorshow.jl

@@ -290,7 +290,7 @@ function showerror_ambiguous(io::IO, meth, f, args)
 end
 
 #Show an error by directly calling jl_printf.
-#Useful in Base submodule __init__ functions where STDERR isn't defined yet.
+#Useful in Base submodule __init__ functions where stderr isn't defined yet.
 function showerror_nostdio(err, msg::AbstractString)
     stderr_stream = ccall(:jl_stderr_stream, Ptr{Cvoid}, ())
     ccall(:jl_printf, Cint, (Ptr{Cvoid},Cstring), stderr_stream, msg)

base/exports.jl

@@ -40,7 +40,6 @@ export
     DenseMatrix,
     DenseVecOrMat,
     DenseVector,
-    DevNull,
     Dict,
     Dims,
     Enum,
@@ -135,10 +134,11 @@ export
     ENV,
     LOAD_PATH,
     PROGRAM_FILE,
-    STDERR,
-    STDIN,
-    STDOUT,
+    stderr,
+    stdin,
+    stdout,
     VERSION,
+    devnull,
 
 # Mathematical constants
     Inf,

base/initdefs.jl

@@ -149,8 +149,8 @@ function _atexit()
         try
             f()
         catch err
-            show(STDERR, err)
-            println(STDERR)
+            show(stderr, err)
+            println(stderr)
         end
     end
 end