Adjust print_response to separate error-printing from result display, remove loop

stdlib/REPL/src/REPL.jl

@@ -578,7 +578,11 @@ function print_response(repl::AbstractREPL, response, show_value::Bool, have_col
     return nothing
 end
 
-function repl_display_error(errio::IO, @nospecialize errval)
+# N.B.: Any functions starting with __repl_entry cut off backtraces when printing in the REPL.
+__repl_entry_display(val) = Base.invokelatest(display, val)
+__repl_entry_display(specialdisplay::Union{AbstractDisplay,Nothing}, val) = Base.invokelatest(display, specialdisplay, val)
+
+function __repl_entry_display_error(errio::IO, @nospecialize errval)
     # this will be set to true if types in the stacktrace are truncated
     limitflag = Ref(false)
     errio = IOContext(errio, :stacktrace_types_limited => limitflag)
@@ -593,53 +597,59 @@ end
 function print_response(errio::IO, response, backend::Union{REPLBackendRef,Nothing}, show_value::Bool, have_color::Bool, specialdisplay::Union{AbstractDisplay,Nothing}=nothing)
     Base.sigatomic_begin()
     val, iserr = response
-    while true
+    if !iserr
+        # display result
         try
-            Base.sigatomic_end()
-            if iserr
-                val = Base.scrub_repl_backtrace(val)
-                Base.istrivialerror(val) || setglobal!(Base.MainInclude, :err, val)
-                repl_display_error(errio, val)
-            else
-                if val !== nothing && show_value
-                    val2, iserr = if specialdisplay === nothing
-                        # display calls may require being run on the main thread
-                        call_on_backend(backend) do
-                            Base.invokelatest(display, val)
-                        end
-                    else
-                        call_on_backend(backend) do
-                            Base.invokelatest(display, specialdisplay, val)
-                        end
+            if val !== nothing && show_value
+                Base.sigatomic_end() # allow display to be interrupted
+                val2, iserr = if specialdisplay === nothing
+                    # display calls may require being run on the main thread
+                    call_on_backend(backend) do
+                        __repl_entry_display(val)
                     end
-                    if iserr
-                        println(errio, "Error showing value of type ", typeof(val), ":")
-                        throw(val2)
+                else
+                    call_on_backend(backend) do
+                        __repl_entry_display(specialdisplay, val)
                     end
                 end
-            end
-            break
-        catch ex
-            if iserr
-                println(errio) # an error during printing is likely to leave us mid-line
-                println(errio, "SYSTEM (REPL): showing an error caused an error")
-                try
-                    excs = Base.scrub_repl_backtrace(current_exceptions())
-                    setglobal!(Base.MainInclude, :err, excs)
-                    repl_display_error(errio, excs)
-                catch e
-                    # at this point, only print the name of the type as a Symbol to
-                    # minimize the possibility of further errors.
+                Base.sigatomic_begin()
+                if iserr
                     println(errio)
-                    println(errio, "SYSTEM (REPL): caught exception of type ", typeof(e).name.name,
-                            " while trying to handle a nested exception; giving up")
+                    println(errio, "Error showing value of type ", typeof(val), ":")
+                    val = val2
                 end
-                break
             end
+        catch ex
+            println(errio)
+            println(errio, "SYSTEM (REPL): showing a value caused an error")
             val = current_exceptions()
             iserr = true
         end
     end
+    if iserr
+        # print error
+        iserr = false
+        while true
+            try
+                Base.sigatomic_end() # allow stacktrace printing to be interrupted
+                val = Base.scrub_repl_backtrace(val)
+                Base.istrivialerror(val) || setglobal!(Base.MainInclude, :err, val)
+                __repl_entry_display_error(errio, val)
+                break
+            catch ex
+                println(errio) # an error during printing is likely to leave us mid-line
+                if !iserr
+                    println(errio, "SYSTEM (REPL): showing an error caused an error")
+                    val = current_exceptions()
+                    iserr = true
+                else
+                    println(errio, "SYSTEM (REPL): caught exception of type ", typeof(ex).name.name,
+                        " while trying to print an exception; giving up")
+                    break
+                end
+            end
+        end
+    end
     Base.sigatomic_end()
     nothing
 end