https://github.com/zsh-users/zsh-autosuggestions/issues/341

See technique used in `fast-syntax-highlighting`:
- ca2e18bbc9
- http://www.zsh.org/mla/users/2018/msg00424.html

Fixes #337

`zpty -r` with a pattern seems to have some funky behavior on older
versions, giving unpredictable results

Need to make sure compinit is called in the pty or the shell hangs

Only a problem in synchronous mode

The `zsh -f` running in the PTY doesn't know about the non-exported
variables and functions defined in the original shell, thus can't make
suggestions for them. Run local functions in the PTY instead of a new
`zsh` process.

We have to handle things differently based on whether zle is active or
not (async vs. sync mode).

Only need the first completion result

Uses https://github.com/Valodim/zsh-capture-completion with some slight
modifications.

For unknown reasons, the pty will occasionally quit running. In these
cases, we still want to remove it so that a fresh one can be created. We
don't actually need this check because error messages from `zle` and
`zpty` are redirected to /dev/null.

One sure way to kill all currently running pty's is to run `exit` in a
subshell. Even without zsh-autosuggestions loaded, the following works:

    % zmodload zsh/zpty
    % zpty -b foo cat
    % zpty -b bar cat
    % zpty
    (31689) bar: cat
    (31666) foo: cat
    % $(exit)
    % zpty
    (finished) bar: cat
    (finished) foo: cat

Issue #188. PR #324.

Thanks to @toadjaune and @IngoHeimbach.

Specific case where this matters is following:

Be in vi insert mode with some text in the buffer and the cursor at the
end of the buffer. Press `esc` to trigger `vi-cmd-mode widget`, then
before the cursor moves (KEYTIMEOUT), press `h` to trigger
`vi-backward-char` widget. When `vi-cmd-mode` original widget exits,
KEYS_QUEUED_COUNT will be non-zero and the suggestion will be lost.

These widgets rely on `$LASTWIDGET` being set to restore the cursor
position. When asynchronous suggestions are enabled, and the widget
triggers a suggestion to be fetched, `autosuggest-suggest` will be
called and $LASTWIDGET will be set to it.

`_zsh_autosuggest_widget_accept()` (&al.) passes this function's return status
on, and ZLE rings the bell if it's >0. Not having an original widget isn't an
error condition, so always returning 0 here should be OK to avoid the bell

Fixes #228

To support older versions of zsh (< 5.0.8).

We were missing the EXTENDED_GLOB option that allows use of `(#m)` flag.

This reverts commit 7f8ff2867c.

This fixes a small issue in src/widgets.zsh which makes it so if you
alias [ to g[ (as is done in prezto if the gnu-utility module is loaded)
autosuggestions would fail.

The documentation for GNU test mentions that -o and -a should be avoided
if possible because it's not very clear. Also, with zsh and [[ -o
actually tests if an option is set, which makes this option even more
confusing.

Now that patch has released

Fixes github issue #271

Maybe this is also a fix for #247, #248 and #258. Supersedes #267.

Testcase:
Using match_prev_cmd strategy and with these lines in history:
echo '1^'
echo '2^'
echo '1^'

type:
echo       (unexpected suggestion echo '1^' instead of echo '2^')
echo '1^1  (wrong suggestion echo '1^1echo '1^')
echo '1^#  (error "bad math expression")

This commit adds the 'emacs-forward-word' widget to the list of partial
accept widgets.

While they are still experimental

[GitHub #219]

Intended to be helpful for folks using bracketed-paste-magic and other
widgets that use `zle -U`.

Depends on patch to ZSH from workers/40702:

  http://www.zsh.org/mla/workers/2017/msg00414.html

Puts in a better fix for #126 and related issues.

There's no need to re-run feature detection or async_start on every
precmd. Just do those once.

Specifically, highlighting breaks if our widgets are wrapped by z-syn-h
widgets.

Should fix #126

So that it doesn't conflict when the file is sourced again

These options have been deprecated for over a year.

It seems like all the zle-* methods are special and shouldn't be
monkeyed with.

Specifically `zle-isearch-update` and friends. Binding that widget
caused `history-incremental-pattern-search` to stop working.

Fixes zsh-users/zsh-syntax-highlighting#387