add :color attribute to IOContext, prefer get(io,:color,false) to Base.have_color

NEWS.md

@@ -338,6 +338,10 @@ Library improvements
   * The function `chop` now accepts two arguments `head` and `tail` allowing to specify
     number of characters to remove from the head and tail of the string ([#24126]).
 
+  * `get(io, :color, false)` can now be used to query whether a stream `io` supports
+    [ANSI color codes](https://en.wikipedia.org/wiki/ANSI_escape_code) ([#25067]),
+    rather than using the undocumented `Base.have_color` global flag.
+
   * Functions `first` and `last` now accept `nchar` argument for `AbstractString`.
     If this argument is used they return a string consisting of first/last `nchar`
     characters from the original string ([#23960]).

base/logging.jl

@@ -485,16 +485,17 @@ function handle_message(logger::SimpleLogger, level, message, _module, group, id
             level < Warn  ? :cyan :
             level < Error ? :yellow : :red
     buf = IOBuffer()
-    print_with_color(color, buf, first(levelstr), "- ", bold=true)
+    iob = IOContext(buf, logger.stream)
+    print_with_color(color, iob, first(levelstr), "- ", bold=true)
     msglines = split(string(message), '\n')
     for i in 1:length(msglines)-1
-        println(buf, msglines[i])
-        print_with_color(color, buf, "|  ", bold=true)
+        println(iob, msglines[i])
+        print_with_color(color, iob, "|  ", bold=true)
     end
-    println(buf, msglines[end], " -", levelstr, ":", _module, ":", basename(filepath), ":", line)
+    println(iob, msglines[end], " -", levelstr, ":", _module, ":", basename(filepath), ":", line)
     for (key,val) in pairs(kwargs)
-        print_with_color(color, buf, "|  ", bold=true)
-        println(buf, key, " = ", val)
+        print_with_color(color, iob, "|  ", bold=true)
+        println(iob, key, " = ", val)
     end
     write(logger.stream, take!(buf))
     nothing

base/markdown/Markdown.jl

@@ -60,10 +60,4 @@ macro doc_str(s::AbstractString, t...)
     docexpr(__source__, __module__, s, t...)
 end
 
-function Base.display(d::Base.REPL.REPLDisplay, mds::Vector{MD})
-    for md in mds
-        display(d, md)
-    end
-end
-
 end

base/markdown/render/terminal/formatting.jl

@@ -18,13 +18,13 @@ const text_formats = Dict(
     :negative  => ("\e[7m", "\e[27m"))
 
 function with_output_format(f::Function, formats::Vector{Symbol}, io::IO, args...)
-    Base.have_color && for format in formats
+    get(io, :color, false) && for format in formats
         haskey(text_formats, format) &&
             print(io, text_formats[format][1])
     end
     try f(io, args...)
     finally
-        Base.have_color && for format in formats
+        get(io, :color, false) && for format in formats
             haskey(text_formats, format) &&
                 print(io, text_formats[format][2])
         end
@@ -58,9 +58,9 @@ words(s) = split(s, " ")
 lines(s) = split(s, "\n")
 
 # This could really be more efficient
-function wrapped_lines(s::AbstractString; width = 80, i = 0)
+function wrapped_lines(io::IO, s::AbstractString; width = 80, i = 0)
     if ismatch(r"\n", s)
-        return vcat(map(s->wrapped_lines(s, width = width, i = i), split(s, "\n"))...)
+        return vcat(map(s->wrapped_lines(io, s, width = width, i = i), split(s, "\n"))...)
     end
     ws = words(s)
     lines = AbstractString[ws[1]]
@@ -78,11 +78,11 @@ function wrapped_lines(s::AbstractString; width = 80, i = 0)
     return lines
 end
 
-wrapped_lines(f::Function, args...; width = 80, i = 0) =
-    wrapped_lines(sprint(f, args...), width = width, i = 0)
+wrapped_lines(io::IO, f::Function, args...; width = 80, i = 0) =
+    wrapped_lines(io, sprint(f, args...; context=io), width = width, i = 0)
 
 function print_wrapped(io::IO, s...; width = 80, pre = "", i = 0)
-    lines = wrapped_lines(s..., width = width, i = i)
+    lines = wrapped_lines(io, s..., width = width, i = i)
     println(io, lines[1])
     for line in lines[2:end]
         println(io, pre, line)
@@ -93,7 +93,7 @@ end
 print_wrapped(f::Function, io::IO, args...; kws...) = print_wrapped(io, f, args...; kws...)
 
 function print_centred(io::IO, s...; columns = 80, width = columns)
-    lines = wrapped_lines(s..., width = width)
+    lines = wrapped_lines(io, s..., width = width)
     for line in lines
         print(io, " "^(div(columns-ansi_length(line), 2)))
         println(io, line)

base/markdown/render/terminal/render.jl

@@ -24,7 +24,7 @@ function term(io::IO, md::Paragraph, columns)
 end
 
 function term(io::IO, md::BlockQuote, columns)
-    s = sprint(term, md.content, columns - 10)
+    s = sprint(term, md.content, columns - 10; context=io)
     for line in split(rstrip(s), "\n")
         println(io, " "^margin, "|", line)
     end
@@ -34,7 +34,7 @@ function term(io::IO, md::Admonition, columns)
     print(io, " "^margin, "| ")
     with_output_format(:bold, print, io, isempty(md.title) ? md.category : md.title)
     println(io, "\n", " "^margin, "|")
-    s = sprint(term, md.content, columns - 10)
+    s = sprint(term, md.content, columns - 10; context=io)
     for line in split(rstrip(s), "\n")
         println(io, " "^margin, "|", line)
     end
@@ -44,7 +44,7 @@ function term(io::IO, f::Footnote, columns)
     print(io, " "^margin, "| ")
     with_output_format(:bold, print, io, "[^$(f.id)]")
     println(io, "\n", " "^margin, "|")
-    s = sprint(term, f.text, columns - 10)
+    s = sprint(term, f.text, columns - 10; context=io)
     for line in split(rstrip(s), "\n")
         println(io, " "^margin, "|", line)
     end
@@ -61,7 +61,7 @@ function term(io::IO, md::List, columns)
 end
 
 function _term_header(io::IO, md, char, columns)
-    text = terminline(md.text)
+    text = terminline_string(io, md.text)
     with_output_format(:bold, io) do io
         print(io, " "^(margin))
         line_no, lastline_width = print_wrapped(io, text,
@@ -103,7 +103,7 @@ term(io::IO, x, _) = show(io, MIME"text/plain"(), x)
 
 # Inline Content
 
-terminline(md) = sprint(terminline, md)
+terminline_string(io::IO, md) = sprint(terminline, md; context=io)
 
 terminline(io::IO, content...) = terminline(io, collect(content))
 
@@ -137,7 +137,7 @@ terminline(io::IO, f::Footnote) = with_output_format(:bold, terminline, io, "[^$
 
 function terminline(io::IO, md::Link)
     url = !Base.startswith(md.url, "@ref") ? " ($(md.url))" : ""
-    text = terminline(md.text)
+    text = terminline_string(io, md.text)
     terminline(io, text, url)
 end
 
@@ -148,5 +148,4 @@ end
 terminline(io::IO, x) = show(io, MIME"text/plain"(), x)
 
 # Show in terminal
-
-Base.display(d::Base.REPL.REPLDisplay, md::MD) = term(Base.REPL.outstream(d.repl), md)
+Base.show(io::IO, ::MIME"text/plain", md::MD) = (term(io, md); nothing)

base/repl/REPL.jl

@@ -122,7 +122,7 @@ end
 
 function display(d::REPLDisplay, mime::MIME"text/plain", x)
     io = outstream(d.repl)
-    Base.have_color && write(io, answer_color(d.repl))
+    get(io, :color, false) && write(io, answer_color(d.repl))
     show(IOContext(io, :limit => true), mime, x)
     println(io)
 end

base/repl/Terminals.jl

@@ -167,4 +167,7 @@ else
     end
 end
 
+# use cached value of have_color
+Base.get(::TTYTerminal, k::Symbol, default) = k === :color ? Base.have_color : default
+
 end # module

base/replutil.jl

@@ -230,7 +230,7 @@ end
 
 function showerror(io::IO, ex, bt; backtrace=true)
     try
-        with_output_color(have_color ? error_color() : :nothing, io) do io
+        with_output_color(get(io, :color, false) ? error_color() : :nothing, io) do io
             showerror(io, ex)
         end
     finally
@@ -488,6 +488,7 @@ function show_method_candidates(io::IO, ex::MethodError, kwargs::NamedTuple = Na
     for (func,arg_types_param) in funcs
         for method in methods(func)
             buf = IOBuffer()
+            iob = IOContext(buf, io)
             tv = Any[]
             sig0 = method.sig
             if Base.is_default_method(method)
@@ -499,20 +500,20 @@ function show_method_candidates(io::IO, ex::MethodError, kwargs::NamedTuple = Na
             end
             s1 = sig0.parameters[1]
             sig = sig0.parameters[2:end]
-            print(buf, "  ")
+            print(iob, "  ")
             if !isa(func, s1)
                 # function itself doesn't match
                 return
             else
                 # TODO: use the methodshow logic here
                 use_constructor_syntax = isa(func, Type)
-                print(buf, use_constructor_syntax ? func : typeof(func).name.mt.name)
+                print(iob, use_constructor_syntax ? func : typeof(func).name.mt.name)
             end
-            print(buf, "(")
+            print(iob, "(")
             t_i = copy(arg_types_param)
             right_matches = 0
             for i = 1 : min(length(t_i), length(sig))
-                i > 1 && print(buf, ", ")
+                i > 1 && print(iob, ", ")
                 # If isvarargtype then it checks whether the rest of the input arguments matches
                 # the varargtype
                 if Base.isvarargtype(sig[i])
@@ -529,20 +530,20 @@ function show_method_candidates(io::IO, ex::MethodError, kwargs::NamedTuple = Na
                 # the type of the first argument is not matched.
                 t_in === Union{} && special && i == 1 && break
                 if t_in === Union{}
-                    if Base.have_color
-                        Base.with_output_color(Base.error_color(), buf) do buf
-                            print(buf, "::$sigstr")
+                    if get(io, :color, false)
+                        Base.with_output_color(Base.error_color(), iob) do iob
+                            print(iob, "::$sigstr")
                         end
                     else
-                        print(buf, "!Matched::$sigstr")
+                        print(iob, "!Matched::$sigstr")
                     end
                     # If there is no typeintersect then the type signature from the method is
                     # inserted in t_i this ensures if the type at the next i matches the type
                     # signature then there will be a type intersect
                     t_i[i] = sig[i]
                 else
                     right_matches += j==i ? 1 : 0
-                    print(buf, "::$sigstr")
+                    print(iob, "::$sigstr")
                 end
             end
             special && right_matches==0 && return # continue the do-block
@@ -569,26 +570,26 @@ function show_method_candidates(io::IO, ex::MethodError, kwargs::NamedTuple = Na
                             sigstr = string(sigtype)
                         end
                         if !((min(length(t_i), length(sig)) == 0) && k==1)
-                            print(buf, ", ")
+                            print(iob, ", ")
                         end
-                        if Base.have_color
-                            Base.with_output_color(Base.error_color(), buf) do buf
-                                print(buf, "::$sigstr")
+                        if get(io, :color, false)
+                            Base.with_output_color(Base.error_color(), iob) do iob
+                                print(iob, "::$sigstr")
                             end
                         else
-                            print(buf, "!Matched::$sigstr")
+                            print(iob, "!Matched::$sigstr")
                         end
                     end
                 end
                 kwords = Symbol[]
                 if isdefined(ft.name.mt, :kwsorter)
                     kwsorter_t = typeof(ft.name.mt.kwsorter)
                     kwords = kwarg_decl(method, kwsorter_t)
-                    length(kwords) > 0 && print(buf, "; ", join(kwords, ", "))
+                    length(kwords) > 0 && print(iob, "; ", join(kwords, ", "))
                 end
-                print(buf, ")")
-                show_method_params(buf, tv)
-                print(buf, " at ", method.file, ":", method.line)
+                print(iob, ")")
+                show_method_params(iob, tv)
+                print(iob, " at ", method.file, ":", method.line)
                 if !isempty(kwargs)
                     unexpected = Symbol[]
                     if isempty(kwords) || !(any(endswith(string(kword), "...") for kword in kwords))
@@ -599,14 +600,14 @@ function show_method_candidates(io::IO, ex::MethodError, kwargs::NamedTuple = Na
                         end
                     end
                     if !isempty(unexpected)
-                        Base.with_output_color(Base.error_color(), buf) do buf
+                        Base.with_output_color(Base.error_color(), iob) do iob
                             plur = length(unexpected) > 1 ? "s" : ""
-                            print(buf, " got unsupported keyword argument$plur \"", join(unexpected, "\", \""), "\"")
+                            print(iob, " got unsupported keyword argument$plur \"", join(unexpected, "\", \""), "\"")
                         end
                     end
                 end
                 if ex.world < min_world(method)
-                    print(buf, " (method too new to be called from this world context.)")
+                    print(iob, " (method too new to be called from this world context.)")
                 end
                 # TODO: indicate if it's in the wrong world
                 push!(lines, (buf, right_matches))

base/show.jl

@@ -20,7 +20,8 @@ struct IOContext{IO_t <: IO} <: AbstractPipe
     end
 end
 
-unwrapcontext(io::IO) = io, ImmutableDict{Symbol,Any}()
+# (Note that TTY and TTYTerminal io types have a :color property.)
+unwrapcontext(io::IO) = io, get(io,:color,false) ? ImmutableDict{Symbol,Any}(:color, true) : ImmutableDict{Symbol,Any}()
 unwrapcontext(io::IOContext) = io.io, io.dict
 
 function IOContext(io::IO, dict::ImmutableDict)
@@ -67,6 +68,9 @@ The following properties are in common use:
    can be avoided (e.g. `[Float16(0)]` can be shown as "Float16[0.0]" instead
    of "Float16[Float16(0.0)]" : while displaying the elements of the array, the `:typeinfo`
    property will be set to `Float16`).
+ - `:color`: Boolean specifying whether ANSI color/escape codes are supported/expected.
+   By default, this is determined by whether `io` is a compatible terminal and by any
+   `--color` command-line flag when `julia` was launched.
 
 # Examples
 ```jldoctest
@@ -715,7 +719,7 @@ function show_expr_type(io::IO, @nospecialize(ty), emph::Bool)
     end
 end
 
-emphasize(io, str::AbstractString) = have_color ?
+emphasize(io, str::AbstractString) = get(io, :color, false) ?
     print_with_color(Base.error_color(), io, str; bold = true) :
     print(io, Unicode.uppercase(str))
 
@@ -1253,7 +1257,7 @@ end
 
 function show_tuple_as_call(io::IO, name::Symbol, sig::Type)
     # print a method signature tuple for a lambda definition
-    color = have_color && get(io, :backtrace, false) ? stackframe_function_color() : :nothing
+    color = get(io, :color, false) && get(io, :backtrace, false) ? stackframe_function_color() : :nothing
     if sig === Tuple
         Base.print_with_color(color, io, name, "(...)")
         return
@@ -1274,7 +1278,7 @@ function show_tuple_as_call(io::IO, name::Symbol, sig::Type)
         end
     end
     first = true
-    print_style = have_color && get(io, :backtrace, false) ? :bold : :nothing
+    print_style = get(io, :color, false) && get(io, :backtrace, false) ? :bold : :nothing
     print_with_color(print_style, io, "(")
     for i = 2:length(sig)  # fixme (iter): `eachindex` with offset?
         first || print(io, ", ")

base/stacktraces.jl

@@ -305,7 +305,7 @@ function show_spec_linfo(io::IO, frame::StackFrame)
         elseif frame.func === top_level_scope_sym
             print(io, "top-level scope")
         else
-            print_with_color(Base.have_color && get(io, :backtrace, false) ? Base.stackframe_function_color() : :nothing, io, string(frame.func))
+            print_with_color(get(io, :color, false) && get(io, :backtrace, false) ? Base.stackframe_function_color() : :nothing, io, string(frame.func))
         end
     elseif frame.linfo isa Core.MethodInstance
         if isa(frame.linfo.def, Method)
@@ -323,7 +323,7 @@ function show(io::IO, frame::StackFrame; full_path::Bool=false)
     if frame.file !== empty_sym
         file_info = full_path ? string(frame.file) : basename(string(frame.file))
         print(io, " at ")
-        Base.with_output_color(Base.have_color && get(io, :backtrace, false) ? Base.stackframe_lineinfo_color() : :nothing, io) do io
+        Base.with_output_color(get(io, :color, false) && get(io, :backtrace, false) ? Base.stackframe_lineinfo_color() : :nothing, io) do io
             print(io, file_info, ":")
             if frame.line >= 0
                 print(io, frame.line)

base/stream.jl

@@ -403,6 +403,7 @@ function displaysize(io::TTY)
     return h, w
 end
 
+get(::TTY, k::Symbol, default) = k === :color ? have_color : default
 
 ### Libuv callbacks ###
 

base/util.jl

@@ -319,12 +319,13 @@ end
 
 function with_output_color(f::Function, color::Union{Int, Symbol}, io::IO, args...; bold::Bool = false)
     buf = IOBuffer()
-    have_color && bold && print(buf, text_colors[:bold])
-    have_color && print(buf, get(text_colors, color, color_normal))
+    iscolor = get(io, :color, false)
+    iscolor && bold && print(buf, text_colors[:bold])
+    iscolor && print(buf, get(text_colors, color, color_normal))
     try f(IOContext(buf, io), args...)
     finally
-        have_color && color != :nothing && print(buf, get(disable_text_style, color, text_colors[:default]))
-        have_color && (bold || color == :bold) && print(buf, disable_text_style[:bold])
+        iscolor && color != :nothing && print(buf, get(disable_text_style, color, text_colors[:default]))
+        iscolor && (bold || color == :bold) && print(buf, disable_text_style[:bold])
         print(io, String(take!(buf)))
     end
 end

base/version.jl

@@ -255,7 +255,7 @@ function banner(io::IO = STDOUT)
     end
     commit_date = !isempty(GIT_VERSION_INFO.date_string) ? " ($(GIT_VERSION_INFO.date_string))" : ""
 
-    if have_color
+    if get(io, :color, false)
         c = text_colors
         tx = c[:normal] # text
         jl = c[:normal] # julia