Bug #6601
closed
[readline] Alt-* commands do not work in reverse-i-search
Description
=begin
= Steps to reproduce
Below are the steps to reproduce from an (({irb})) session. ^ is used to denote the cursor position on the screen.
-
Type ((%puts :a%)) then ((%Enter%)). This is to populate the history for reverse-i-search.
irb(main):001:0> puts :a
a
=> nil -
Hit ((%Ctrl-R%)) (for reverse-i-search), followed by ((%u%)):
(reverse-i-search)`u': puts :a
^ -
Hit ((%Alt-F%)) (for forward-word).
Observed: reverse-i-search terminated, with an 'f' inserted at cursor position.
irb(main):002:0> pfuts :a
^
Expected: reverse-i-search terminated, nothing inserted, cursor moves to end of the word (({puts})):
irb(main):002:0> puts :a
^
Note that other ((%Alt-*%)) commands don't work too (ie ((%x%)) is inserted instead of the command ((%Alt-x%)) being performed), including
- ((%Alt-B%)) (move backward a word)
- ((%Alt-C%)) (capitalize letter)
- ((%Alt-D%)) (delete till end of word)
= Fix
When we hit ((%Alt-F%)) from reverse-i-search, execution arrives at this piece of code in libreadline's (({isearch.c})):
387 /* ESC still terminates the search, but if there is pending
388 input or if input arrives within 0.1 seconds (on systems
389 with select(2)) it is used as a prefix character
390 with rl_execute_next. WATCH OUT FOR THIS! This is intended
391 to allow the arrow keys to be used like ^F and ^B are used
392 to terminate the search and execute the movement command.
393 XXX - since _rl_input_available depends on the application-
394 settable keyboard timeout value, this could alternatively
395 use _rl_input_queued(100000) */
396 if (cxt->lastc == ESC && _rl_input_available ())
397 rl_execute_next (ESC);
Due to (({readline_getc()})), our (({rl_getc_function()})) implementation, (({IO::getbyte()})) is called, causing all input characters to be "swallowed" into our byte buffer in (({readline_instream})). Thus (({_rl_input_available()})) incorrectly returns false, and the keystrokes (eg. Alt, F) fail to be recognized as a binding for a command.
The proposed fix (attached) uses (({rb_io_read_pending()})) to emulate (({_rl_input_available()})), and calls (({rl_execute_next()})), as libreadline does.
= Affected Versions
Ruby trunk and 1.9.3 (latest) exhibits this issue.
Ruby 1.8 also has exhibits this issue, but the fix would be different since (({rl_getc_function()})) isn't overriden in (({ext/readline/readline.c})).
Tested on readline 6.2; blame'ing the above snippet shows that readline as far back as 5.1 should also give this behaviour.
=end
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