RFC: print error messages in REPL with colors and structure

base/REPL.jl

@@ -111,15 +111,13 @@ function ip_matches_func(ip, func::Symbol)
 end
 
 function display_error(io::IO, er, bt)
-    Base.with_output_color(:red, io) do io
-        print(io, "ERROR: ")
-        # remove REPL-related frames from interactive printing
-        eval_ind = findlast(addr->ip_matches_func(addr, :eval), bt)
-        if eval_ind != 0
-            bt = bt[1:eval_ind-1]
-        end
-        Base.showerror(IOContext(io, :limit => true), er, bt)
+    print_with_color(:red, io, "ERROR: ")
+    # remove REPL-related frames from interactive printing
+    eval_ind = findlast(addr->Base.REPL.ip_matches_func(addr, :eval), bt)
+    if eval_ind != 0
+        bt = bt[1:eval_ind-1]
     end
+    showerror(IOContext(IOContext(io, :hascolor => true), :limit => true), er, bt)
 end
 
 immutable REPLDisplay{R<:AbstractREPL} <: Display
@@ -167,6 +165,8 @@ function print_response(errio::IO, val::ANY, bt, show_value::Bool, have_color::B
         catch err
             if bt !== nothing
                 println(errio, "SYSTEM: show(lasterr) caused an error")
+                println(errio, err)
+                Base.show_backtrace(errio, bt)
                 break
             end
             val = err

base/client.jl

@@ -14,6 +14,7 @@ const text_colors = AnyDict(
     :white   => "\033[1m\033[37m",
     :normal  => "\033[0m",
     :bold    => "\033[1m",
+    :nothing => "",
 )
 
 for i in 0:255
@@ -35,6 +36,7 @@ const available_text_colors_docstring =
 """Dictionary of color codes for the terminal.
 
 Available colors are: $available_text_colors_docstring as well as the integers 0 to 255 inclusive.
+Printing with the color `:nothing` will print the string without modifications.
 """
 text_colors
 
@@ -61,6 +63,8 @@ warn_color()   = repl_color("JULIA_WARN_COLOR", default_color_warn)
 info_color()   = repl_color("JULIA_INFO_COLOR", default_color_info)
 input_color()  = text_colors[repl_color("JULIA_INPUT_COLOR", default_color_input)]
 answer_color() = text_colors[repl_color("JULIA_ANSWER_COLOR", default_color_answer)]
+stackframe_lineinfo_color() = repl_color("JULIA_STACKFRAME_LINEINFO_COLOR", :bold)
+stackframe_function_color() = repl_color("JULIA_STACKFRAME_FUNCTION_COLOR", :bold)
 
 function repl_cmd(cmd, out)
     shell = shell_split(get(ENV,"JULIA_SHELL",get(ENV,"SHELL","/bin/sh")))

base/replutil.jl

@@ -194,9 +194,13 @@ end
 
 function showerror(io::IO, ex, bt; backtrace=true)
     try
-        showerror(io, ex)
+        with_output_color(get(io, :hascolor, false) ? :red : :nothing, io) do io
+            showerror(io, ex)
+        end
     finally
-        backtrace && show_backtrace(io, bt)
+        if backtrace
+            show_backtrace(io, bt)
+        end
     end
 end
 
@@ -559,15 +563,22 @@ function show_method_candidates(io::IO, ex::MethodError, kwargs::Vector=Any[])
     end
 end
 
-function show_trace_entry(io, frame, n)
+function show_trace_entry(io, frame, n; prefix = " in ")
     print(io, "\n")
-    show(io, frame, full_path=true)
+    show(io, frame, full_path=true; prefix = prefix)
     n > 1 && print(io, " (repeats ", n, " times)")
 end
 
 function show_backtrace(io::IO, t::Vector)
-    process_entry(last_frame, n) =
-        show_trace_entry(io, last_frame, n)
+    n_frames = 0
+    frame_counter = 0
+    process_backtrace((a,b) -> n_frames += 1, t)
+    n_frames != 0 && print(io, "\n\nStacktrace:")
+    process_entry = (last_frame, n) -> begin
+        frame_counter += 1
+        n_spaces_align = ndigits(n_frames) - ndigits(frame_counter) + 1
+        show_trace_entry(io, last_frame, n, prefix = string(" "^n_spaces_align, "[", frame_counter, "] "))
+    end
     process_backtrace(process_entry, t)
 end
 

base/show.jl

@@ -1030,31 +1030,37 @@ end
 
 function show_lambda_types(io::IO, li::Core.MethodInstance)
     # print a method signature tuple for a lambda definition
-    if li.specTypes === Tuple
-        print(io, li.def.name, "(...)")
-        return
-    end
-
-    sig = li.specTypes.parameters
-    ft = sig[1]
-    if ft <: Function && isempty(ft.parameters) &&
-            isdefined(ft.name.module, ft.name.mt.name) &&
-            ft == typeof(getfield(ft.name.module, ft.name.mt.name))
-        print(io, ft.name.mt.name)
-    elseif isa(ft, DataType) && ft.name === Type.name && isleaftype(ft)
-        f = ft.parameters[1]
-        print(io, f)
-    else
-        print(io, "(::", ft, ")")
+    local sig
+    returned_from_do = false
+    Base.with_output_color(get(io, :hascolor, false) ? stackframe_function_color() : :nothing, io) do io
+        if li.specTypes === Tuple
+            print(io, li.def.name, "(...)")
+            returned_from_do = true
+            return
+        end
+        sig = li.specTypes.parameters
+        ft = sig[1]
+        if ft <: Function && isempty(ft.parameters) &&
+                isdefined(ft.name.module, ft.name.mt.name) &&
+                ft == typeof(getfield(ft.name.module, ft.name.mt.name))
+            print(io, ft.name.mt.name)
+        elseif isa(ft, DataType) && ft.name === Type.name && isleaftype(ft)
+            f = ft.parameters[1]
+            print(io, f)
+        else
+            print(io, "(::", ft, ")")
+        end
     end
+    returned_from_do && return
     first = true
-    print(io, '(')
+    print_style = get(io, :hascolor, false) ? :bold : :nothing
+    print_with_color(print_style, io, "(")
     for i = 2:length(sig)  # fixme (iter): `eachindex` with offset?
         first || print(io, ", ")
         first = false
         print(io, "::", sig[i])
     end
-    print(io, ')')
+    print_with_color(print_style, io, ")")
     nothing
 end
 

base/stacktraces.jl

@@ -188,7 +188,7 @@ function show_spec_linfo(io::IO, frame::StackFrame)
         if frame.func === empty_sym
             @printf(io, "ip:%#x", frame.pointer)
         else
-            print(io, frame.func)
+            print_with_color(get(io, :hascolor, false) ? Base.stackframe_function_color() : :nothing, io, string(frame.func))
         end
     else
         linfo = get(frame.linfo)
@@ -200,16 +200,20 @@ function show_spec_linfo(io::IO, frame::StackFrame)
     end
 end
 
-function show(io::IO, frame::StackFrame; full_path::Bool=false)
-    print(io, " in ")
+function show(io::IO, frame::StackFrame; full_path::Bool=false,
+              prefix = " in ")
+    print(io, prefix)
     show_spec_linfo(io, frame)
     if frame.file !== empty_sym
         file_info = full_path ? string(frame.file) : basename(string(frame.file))
-        print(io, " at ", file_info, ":")
-        if frame.line >= 0
-            print(io, frame.line)
-        else
-            print(io, "?")
+        print(io, " at ")
+        Base.with_output_color(get(io, :hascolor, false) ? Base.stackframe_lineinfo_color() : :nothing, io) do io
+            print(io, file_info, ":")
+            if frame.line >= 0
+                print(io, frame.line)
+            else
+                print(io, "?")
+            end
         end
     end
     if frame.inlined

base/util.jl

@@ -308,7 +308,7 @@ function with_output_color(f::Function, color::Union{Int, Symbol}, io::IO, args.
     have_color && print(buf, get(text_colors, color, color_normal))
     try f(IOContext(buf, io), args...)
     finally
-        have_color && print(buf, color_normal)
+        have_color && color != :nothing && print(buf, color_normal)
         print(io, String(take!(buf)))
     end
 end

test/cmdlineargs.jl

@@ -328,12 +328,12 @@ end
 for precomp in ("yes", "no")
     bt = readstring(pipeline(ignorestatus(`$(Base.julia_cmd()) --startup-file=no --precompiled=$precomp
         -E 'include("____nonexistent_file")'`), stderr=catcmd))
-    @test contains(bt, "in include_from_node1")
+    @test contains(bt, "include_from_node1")
     if is_windows() && Sys.WORD_SIZE == 32 && precomp == "yes"
         # fixme, issue #17251
-        @test_broken contains(bt, "in include_from_node1(::String) at $(joinpath(".","loading.jl"))")
+        @test_broken contains(bt, "include_from_node1(::String) at $(joinpath(".","loading.jl"))")
     else
-        @test contains(bt, "in include_from_node1(::String) at $(joinpath(".","loading.jl"))")
+        @test contains(bt, "include_from_node1(::String) at $(joinpath(".","loading.jl"))")
     end
     lno = match(r"at \.[\/\\]loading\.jl:(\d+)", bt)
     @test length(lno.captures) == 1

test/compile.jl

@@ -209,7 +209,7 @@ try
           end
           """)
 
-    t = redirected_stderr("ERROR: LoadError: Declaring __precompile__(false) is not allowed in files that are being precompiled.\n in __precompile__")
+    t = redirected_stderr("ERROR: LoadError: Declaring __precompile__(false) is not allowed in files that are being precompiled.\n\nStacktrace:\n [1] __precompile__")
     try
         Base.compilecache("Baz") # from __precompile__(false)
         error("__precompile__ disabled test failed")
@@ -306,7 +306,7 @@ try
           error("break me")
           end
           """)
-    t = redirected_stderr("ERROR: LoadError: break me\n in error")
+    t = redirected_stderr("ERROR: LoadError: break me\n\nStacktrace:\n [1] error")
     try
         Base.require(:FooBar)
         error("\"LoadError: break me\" test failed")