RFC hide func args in backtrace by default

NEWS.md

@@ -14,6 +14,9 @@ New language features
 Language changes
 ----------------
 
+ * Function definition arguments are now by default hidden in the backtrace of error messages in the REPL.
+   To re enable this, you can add `ENV["JULIA_ARGS_BACKTRACE"] = ""` to your `.juliarc` file.
+
 Breaking changes
 ----------------
 

base/REPL.jl

@@ -110,16 +110,31 @@ function ip_matches_func(ip, func::Symbol)
     return false
 end
 
+global last_err = nothing
+
 function display_error(io::IO, er, bt)
+    global last_err
+    last_err = 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(io, er, bt)
+        Base.showerror(IOContext(io, :hide_args_in_signature => !haskey(ENV, "JULIA_ARGS_BACKTRACE")), er, bt)
+    end
+end
+
+"""
+Reshows the latest error that the REPL showed.
+"""
+function show_lasterror()
+    global last_err
+    if last_err == nothing
+        error("no error has yet been shown")
     end
+    display_error(outstream(Base.active_repl), last_err[1], last_err[2])
 end
 
 immutable REPLDisplay{R<:AbstractREPL} <: Display

base/show.jl

@@ -1008,8 +1008,10 @@ function show_unquoted(io::IO, ex::Expr, indent::Int, prec::Int)
     nothing
 end
 
+# print a method signature tuple for a lambda definition
+# if ::hide_args_in_signature is true for the io the
+# arguments in the signatures will not be printed
 function show_lambda_types(io::IO, li::LambdaInfo)
-    # print a method signature tuple for a lambda definition
     if li.specTypes === Tuple
         print(io, li.def.name, "(...)")
         return
@@ -1027,14 +1029,16 @@ function show_lambda_types(io::IO, li::LambdaInfo)
     else
         print(io, "(::", ft, ")")
     end
-    first = true
-    print(io, '(')
-    for i = 2:length(sig)  # fixme (iter): `eachindex` with offset?
-        first || print(io, ", ")
-        first = false
-        print(io, "::", sig[i])
+    if !get(io, :hide_args_in_signature, false)
+        first = true
+        print(io, '(')
+        for i = 2:length(sig)  # fixme (iter): `eachindex` with offset?
+            first || print(io, ", ")
+            first = false
+            print(io, "::", sig[i])
+        end
+        print(io, ')')
     end
-    print(io, ')')
     nothing
 end
 

doc/manual/interacting-with-julia.rst

@@ -304,3 +304,13 @@ informational messages in cyan you can add the following to your ``juliarc.jl``
 
     ENV["JULIA_WARN_COLOR"] = :yellow
     ENV["JULIA_INFO_COLOR"] = :cyan
+
+Customizing Error Messages
+--------------------------
+
+By default Julia will not show the arguments for the functions in a backtrace since this can lead to quite large error messages.
+It is possible to activate this by adding the following to your ``juliarc.jl`` file::
+
+    ENV["JULIA_ARGS_BACKTRACE"] = ""
+
+The last error message showed in the REPL can be showed again with `Base.REPL.show_lasterror()`.