[ruby/reline] Ignore unhandled escape sequences

(https://github.com/ruby/reline/pull/522)

* Add unassigned escape sequence matcher to KeyStroke

* Do not insert ESC and unassigned ESC+key to input buffer

2 files changed, 60 insertions, 12 deletions

diff --git a/lib/reline/key_stroke.rb b/lib/reline/key_stroke.rb
index c1c61513a9..bceffbb53f 100644
--- a/lib/reline/key_stroke.rb
+++ b/lib/reline/key_stroke.rb
@@ -1,4 +1,8 @@
 class Reline::KeyStroke
+  ESC_BYTE = 27
+  CSI_PARAMETER_BYTES_RANGE = 0x30..0x3f
+  CSI_INTERMEDIATE_BYTES_RANGE = (0x20..0x2f)
+
   def initialize(config)
     @config = config
   end
@@ -73,17 +77,26 @@ class Reline::KeyStroke
       return :matched  if it.max_by(&:size)&.size&.< input.size
       return :matching if it.size > 1
     }
-    key_mapping.keys.select { |lhs|
-      start_with?(input, lhs)
-    }.tap { |it|
-      return it.size > 0 ? :matched : :unmatched
-    }
+    if key_mapping.keys.any? { |lhs| start_with?(input, lhs) }
+      :matched
+    else
+      match_unknown_escape_sequence(input).first
+    end
   end
 
   def expand(input)
-    input = compress_meta_key(input)
     lhs = key_mapping.keys.select { |item| start_with?(input, item) }.sort_by(&:size).last
-    return input unless lhs
+    unless lhs
+      status, size = match_unknown_escape_sequence(input)
+      case status
+      when :matched
+        return [:ed_unassigned] + expand(input.drop(size))
+      when :matching
+        return [:ed_unassigned]
+      else
+        return input
+      end
+    end
     rhs = key_mapping[lhs]
 
     case rhs
@@ -99,6 +112,36 @@ class Reline::KeyStroke
 
   private
 
+  # returns match status of CSI/SS3 sequence and matched length
+  def match_unknown_escape_sequence(input)
+    idx = 0
+    return [:unmatched, nil] unless input[idx] == ESC_BYTE
+    idx += 1
+    idx += 1 if input[idx] == ESC_BYTE
+
+    case input[idx]
+    when nil
+      return [:matching, nil]
+    when 91 # == '['.ord
+      # CSI sequence
+      idx += 1
+      idx += 1 while idx < input.size && CSI_PARAMETER_BYTES_RANGE.cover?(input[idx])
+      idx += 1 while idx < input.size && CSI_INTERMEDIATE_BYTES_RANGE.cover?(input[idx])
+      input[idx] ? [:matched, idx + 1] : [:matching, nil]
+    when 79 # == 'O'.ord
+      # SS3 sequence
+      input[idx + 1] ? [:matched, idx + 2] : [:matching, nil]
+    else
+      if idx == 1
+        # `ESC char`, make it :unmatched so that it will be handled correctly in `read_2nd_character_of_key_sequence`
+        [:unmatched, nil]
+      else
+        # `ESC ESC char`
+        [:matched, idx + 1]
+      end
+    end
+  end
+
   def key_mapping
     @config.key_bindings
   end
diff --git a/lib/reline/line_editor.rb b/lib/reline/line_editor.rb
index 4030902139..7ad56a39f8 100644
--- a/lib/reline/line_editor.rb
+++ b/lib/reline/line_editor.rb
@@ -1514,11 +1514,13 @@ class Reline::LineEditor
       return if key.char >= 128 # maybe, first byte of multi byte
       method_symbol = @config.editing_mode.get_method(key.combined_char)
       if key.with_meta and method_symbol == :ed_unassigned
-        # split ESC + key
-        method_symbol = @config.editing_mode.get_method("\e".ord)
-        process_key("\e".ord, method_symbol)
-        method_symbol = @config.editing_mode.get_method(key.char)
-        process_key(key.char, method_symbol)
+        if @config.editing_mode_is?(:vi_command, :vi_insert)
+          # split ESC + key in vi mode
+          method_symbol = @config.editing_mode.get_method("\e".ord)
+          process_key("\e".ord, method_symbol)
+          method_symbol = @config.editing_mode.get_method(key.char)
+          process_key(key.char, method_symbol)
+        end
       else
         process_key(key.combined_char, method_symbol)
       end
@@ -3290,4 +3292,7 @@ class Reline::LineEditor
     @mark_pointer = new_pointer
   end
   alias_method :exchange_point_and_mark, :em_exchange_mark
+
+  private def em_meta_next(key)
+  end
 end