REPL: enable "redo" after "undo"

base/repl/LineEdit.jl

@@ -68,6 +68,7 @@ mutable struct PromptState <: ModeState
  p::Prompt
  input_buffer::IOBuffer
  undo_buffers::Vector{IOBuffer}
+ undo_idx::Int
  ias::InputAreaState
  # indentation of lines which do not include the prompt
  # if negative, the width of the prompt is used
@@ -1668,7 +1669,8 @@ AnyDict(
  # Meta Enter
  "\e\r" => (s,o...)->edit_insert_newline(s),
  "\e\n" => "\e\r",
- "^_" => (s,o...)->(pop_undo(s) ? refresh_line(s) : beep(terminal(s))),
+ "^_" => (s,o...)->edit_undo!(s),
+ "\e_" => (s,o...)->edit_redo!(s),
  # Simply insert it into the buffer by default
  "*" => (s,data,c)->(edit_insert(s, c)),
  "^U" => (s,o...)->edit_clear(s),
@@ -1855,7 +1857,7 @@ end
 run_interface(::Prompt) = nothing
 
 init_state(terminal, prompt::Prompt) =
- PromptState(terminal, prompt, IOBuffer(), IOBuffer[], InputAreaState(1, 1),
+ PromptState(terminal, prompt, IOBuffer(), IOBuffer[], 0, InputAreaState(1, 1),
  #=indent(spaces)=# -1)
 
 function init_state(terminal, m::ModalInterface)
@@ -1894,20 +1896,59 @@ position(s::Union{MIState,ModeState}) = position(buffer(s))
 
 function empty_undo(s::PromptState)
  empty!(s.undo_buffers)
+ s.undo_idx = 0
 end
+
 empty_undo(s) = nothing
 
 function push_undo(s::PromptState)
- push!(s.undo_buffers, copy(s.input_buffer))
+ resize!(s.undo_buffers, s.undo_idx += 1)
+ s.undo_buffers[end] = copy(s.input_buffer)
 end
+
 push_undo(s) = nothing
 
+# must be called after a push_undo
 function pop_undo(s::PromptState)
- length(s.undo_buffers) > 0 || return false
- s.input_buffer = pop!(s.undo_buffers)
+ pop!(s.undo_buffers)
+ s.undo_idx -= 1
+end
+
+function edit_undo!(s::MIState)
+ s.last_action ∉ [:edit_redo!, :edit_undo!] && push_undo(s)
+ if edit_undo!(s.mode_state[s.current_mode])
+ :edit_undo!
+ else
+ s.last_action ∉ [:edit_redo!, :edit_undo!] && pop_undo(s)
+ beep(terminal(s))
+ :ignore
+ end
+end
+
+function edit_undo!(s::PromptState)
+ s.undo_idx > 1 || return false
+ s.input_buffer = s.undo_buffers[s.undo_idx -=1]
+ refresh_line(s)
+ true
+end
+edit_undo!(s) = nothing
+
+function edit_redo!(s::MIState)
+ if s.last_action ∈ [:edit_redo!, :edit_undo!] && edit_redo!(s.mode_state[s.current_mode])
+ :edit_redo!
+ else
+ beep(terminal(s))
+ :ignore
+ end
+end
+
+function edit_redo!(s::PromptState)
+ s.undo_idx < length(s.undo_buffers) || return false
+ s.input_buffer = s.undo_buffers[s.undo_idx += 1]
+ refresh_line(s)
  true
 end
-pop_undo(s) = nothing
+edit_redo!(s) = nothing
 
 keymap(s::PromptState, prompt::Prompt) = prompt.keymap_dict
 keymap_data(s::PromptState, prompt::Prompt) = prompt.keymap_func_data