REPL: implement a kill ring

Fixes part of #8447.

base/repl/LineEdit.jl

@@ -37,17 +37,22 @@ end
 
 show(io::IO, x::Prompt) = show(io, string("Prompt(\"", prompt_string(x.prompt), "\",...)"))
 
+"Maximum number of entries in the kill ring queue.
+Beyond this number, oldest entries are discarded first."
+const KILL_RING_MAX = Ref(100)
+
 mutable struct MIState
  interface::ModalInterface
  current_mode::TextInterface
  aborted::Bool
  mode_state::Dict
- kill_buffer::String
+ kill_ring::Vector{String}
+ kill_idx::Int
  previous_key::Vector{Char}
  key_repeats::Int
  last_action::Symbol
 end
-MIState(i, c, a, m) = MIState(i, c, a, m, "", Char[], 0, :begin)
+MIState(i, c, a, m) = MIState(i, c, a, m, String[], 0, Char[], 0, :begin)
 
 function show(io::IO, s::MIState)
  print(io, "MI State (", s.current_mode, " active)")
@@ -478,7 +483,7 @@ function splice_buffer!(buf::IOBuffer, r::UnitRange{<:Integer}, ins::AbstractStr
  seek(buf, pos - length(r))
  end
  if first(r) < buf.mark <= last(r)
- unmark(buf)
+ buf.mark = first(r)
  elseif buf.mark > last(r) && !isempty(r)
  buf.mark += sizeof(ins) - length(r)
  end
@@ -618,11 +623,40 @@ function edit_delete_next_word(s)
 end
 
 function edit_yank(s::MIState)
- edit_insert(buffer(s), s.kill_buffer)
+ if isempty(s.kill_ring)
+ beep(terminal(s))
+ return :ignore
+ end
+ setmark(s) # necessary for edit_yank_pop
+ edit_insert(buffer(s), s.kill_ring[mod1(s.kill_idx, end)])
  refresh_line(s)
  :edit_yank
 end
 
+function edit_yank_pop(s::MIState, require_previous_yank=true)
+ if require_previous_yank && !(s.last_action in [:edit_yank, :edit_yank_pop]) ||
+ isempty(s.kill_ring)
+ beep(terminal(s))
+ :ignore
+ else
+ splice_buffer!(buffer(s), region(s), s.kill_ring[mod1(s.kill_idx-=1, end)])
+ refresh_line(s)
+ :edit_yank_pop
+ end
+end
+
+function push_kill!(s::MIState, killed::String, concat=false)
+ isempty(killed) && return false
+ if concat
+ s.kill_ring[end] *= killed
+ else
+ push!(s.kill_ring, killed)
+ length(s.kill_ring) > KILL_RING_MAX[] && shift!(s.kill_ring)
+ end
+ s.kill_idx = endof(s.kill_ring)
+ true
+end
+
 function edit_kill_line(s::MIState)
  buf = buffer(s)
  pos = position(buf)
@@ -631,40 +665,27 @@ function edit_kill_line(s::MIState)
  killbuf = killbuf[1:end-1]
  char_move_left(buf)
  end
- if !isempty(killbuf)
- s.kill_buffer = s.key_repeats > 0 ? s.kill_buffer * killbuf : killbuf
- splice_buffer!(buf, pos:position(buf)-1)
- refresh_line(s)
- :edit_kill_line
- else
- :ignore
- end
+ push_kill!(s, killbuf, s.key_repeats > 0) || return :ignore
+ splice_buffer!(buf, pos:position(buf)-1)
+ refresh_line(s)
+ :edit_kill_line
 end
 
 function edit_copy_region(s::MIState)
  buf = buffer(s)
- if edit_exchange_point_and_mark(buf) # region non-empty
- s.kill_buffer = String(buf.data[region(buf)+1])
- if REGION_ANIMATION_DURATION[] > 0.0
- refresh_line(s)
- sleep(REGION_ANIMATION_DURATION[])
- end
- edit_exchange_point_and_mark(s) # includes refresh_line
- :edit_copy_region
- else
- :ignore
+ push_kill!(s, String(buf.data[region(buf)+1])) || return :ignore
+ if REGION_ANIMATION_DURATION[] > 0.0
+ edit_exchange_point_and_mark(s)
+ sleep(REGION_ANIMATION_DURATION[])
+ edit_exchange_point_and_mark(s)
  end
+ :edit_copy_region
 end
 
 function edit_kill_region(s::MIState)
- reg = region(s)
- if !isempty(reg)
- s.kill_buffer = splice_buffer!(buffer(s), reg)
- refresh_line(s)
- :edit_kill_region
- else
- :ignore
- end
+ push_kill!(s, splice_buffer!(buffer(s), region(s))) || return :ignore
+ refresh_line(s)
+ :edit_kill_region
 end
 
 function edit_transpose(s::MIState)
@@ -1552,6 +1573,7 @@ AnyDict(
  "^U" => (s,o...)->edit_clear(s),
  "^K" => (s,o...)->edit_kill_line(s),
  "^Y" => (s,o...)->edit_yank(s),
+ "\ey" => (s,o...)->edit_yank_pop(s),
  "\ew" => (s,o...)->edit_copy_region(s),
  "\eW" => (s,o...)->edit_kill_region(s),
  "^A" => (s,o...)->(move_line_start(s); refresh_line(s)),