Migrate sorin prompt to zsh-async (#1385)

This includes some improvements by @indrajitr in addition to the main migration.

The first step was to avoid PROMPT and RPROMPT modification when possible (which may help resolve some other issues as well relating to zsh crashes with the sorin prompt) then update the displayed git information in a separate variable rather than a command.

We use zsh-async for creating and running background tasks. The sorin prompt uses it to update git info without blocking the prompt from displaying (because of how long it can take). In the future it may be worth moving more tasks and more prompts to using this.

The move to zsh-async does make the git prompt slower in some circumstances (most noticeable in large repos), but this is a worthwhile tradeoff to avoid the cache file which had a number of potential security holes.

We have also switched to adding zsh-async as an external submodule (rather than the version bundled with pure) which may cause some migration headaches, but it will be worth it in the long run.

.gitmodules

@@ -22,3 +22,6 @@
 [submodule "modules/fasd/external"]
 	path = modules/fasd/external
 	url = https://github.com/clvv/fasd.git
+[submodule "modules/prompt/external/async"]
+	path = modules/prompt/external/async
+	url = https://github.com/mafredri/zsh-async.git

modules/prompt/external/async

@@ -0,0 +1 @@
+Subproject commit 28c7a644227a5ad7249193525ef27734781f6a63

modules/prompt/functions/async

@@ -1 +1 @@
-../external/pure/async.zsh
+../external/async/async.zsh

modules/prompt/functions/prompt_sorin_setup

@@ -32,49 +32,33 @@
 # Load dependencies.
 pmodload 'helper'
 
-prompt_sorin_git_info() {
-  if (( _prompt_sorin_precmd_async_pid > 0 )); then
-    # Append Git status.
-    if [[ -s "$_prompt_sorin_precmd_async_data" ]]; then
-      alias typeset='typeset -g'
-      source "$_prompt_sorin_precmd_async_data"
-      RPROMPT+='${git_info:+${(e)git_info[status]}}'
-      unalias typeset
+function prompt_sorin_git_info {
+  # We can safely split on ':' because it isn't allowed in ref names.
+  IFS=':' read _git_target _git_post_target <<<"$3"
+
+  # The target actually contains 3 space separated possibilities, so we need to
+  # make sure we grab the first one.
+  _git_target=$(coalesce ${(@)${(z)_git_target}})
+
+  if [[ -z "$_git_target" ]]; then
+    # No git target detected, flush the git fragment and redisplay the prompt.
+    if [[ -n "$_prompt_sorin_git" ]]; then
+      _prompt_sorin_git=''
+      zle && zle reset-prompt
     fi
-
-    # Reset PID.
-    _prompt_sorin_precmd_async_pid=0
-
-    # Redisplay prompt.
+  else
+    # Git target detected, update the git fragment and redisplay the prompt.
+    _prompt_sorin_git="${_git_target}${_git_post_target}"
     zle && zle reset-prompt
   fi
 }
 
-function prompt_sorin_precmd_async {
-  # Get Git repository information.
+function prompt_sorin_async_git {
+  cd -q "$1"
   if (( $+functions[git-info] )); then
     git-info
-    ### TODO XXX
-    # This section exists to patch over vulnerabilities when sourcing the
-    # file in $_prompt_sorin_precmd_async_data. Without it if a branch is named
-    # $foo it will expand if we have a $foo variable, and a branch named
-    # $(IFS=_;cmd=rm_-rf_~;$cmd) could delete the users home directory.
-    # This is a stopgap to prevent code execution and fix the vulnerability,
-    # but it eventually needs to be removed in favor of zsh_async and not using
-    # a file to store the prompt data in.
-    ###
-    local tmp_prompt_var=$(typeset -p git_info)
-    # Replace all $ with $\ to escape
-    tmp_prompt_var=${tmp_prompt_var//\$/\\$}
-    # Unescape the first \$ as it's our $( )
-    tmp_prompt_var=${tmp_prompt_var:s/\\$/\$}
-    # Escape all backticks ` to \`
-    tmp_prompt_var=${tmp_prompt_var//\`/\\\`}
-    printf "%s\n" "$tmp_prompt_var" >! "$_prompt_sorin_precmd_async_data"
+    print ${git_info[status]}
   fi
-
-  # Signal completion to parent process.
-  kill -WINCH $$
 }
 
 function prompt_sorin_precmd {
@@ -84,18 +68,21 @@ function prompt_sorin_precmd {
   # Format PWD.
   _prompt_sorin_pwd=$(prompt-pwd)
 
-  # Define prompts.
-  RPROMPT='${editor_info[overwrite]}%(?:: %F{1}⏎%f)${VIM:+" %B%F{6}V%f%b"}'
-
   # Kill the old process of slow commands if it is still running.
-  if (( _prompt_sorin_precmd_async_pid > 0 )); then
-    kill -KILL "$_prompt_sorin_precmd_async_pid" &>/dev/null
+  async_flush_jobs async_sorin_git
+
+  # Handle updating git data. We also clear the git prompt data if we're in a
+  # different git root now.
+  if (( $+functions[git-dir] )); then
+    local new_git_root="$(git-dir 2>/dev/null)"
+    if [[ $new_git_root != $_sorin_cur_git_root ]]; then
+      _prompt_sorin_git=''
+      _sorin_cur_git_root=$new_git_root
+    fi
   fi
 
   # Compute slow commands in the background.
-  trap prompt_sorin_git_info WINCH
-  prompt_sorin_precmd_async &!
-  _prompt_sorin_precmd_async_pid=$!
+  async_job async_sorin_git prompt_sorin_async_git "$PWD"
 }
 
 function prompt_sorin_setup {
@@ -107,6 +94,7 @@ function prompt_sorin_setup {
 
   # Load required functions.
   autoload -Uz add-zsh-hook
+  autoload -Uz async && async
 
   # Add hook for calling git-info before each command.
   add-zsh-hook precmd prompt_sorin_precmd
@@ -133,11 +121,19 @@ function prompt_sorin_setup {
   zstyle ':prezto:module:git:info:unmerged' format ' %%B%F{3}═%f%%b'
   zstyle ':prezto:module:git:info:untracked' format ' %%B%F{7}◼%f%%b'
   zstyle ':prezto:module:git:info:keys' format \
-    'status' '$(coalesce "%b" "%p" "%c")%s%A%B%S%a%d%m%r%U%u'
+    'status' '%b %p %c:%s%A%B%S%a%d%m%r%U%u'
+
+  # Get the async worker set up
+  async_start_worker async_sorin_git -n
+  async_register_callback async_sorin_git prompt_sorin_git_info
+  _sorin_cur_git_root=''
+
+  _prompt_sorin_git=''
+  _prompt_sorin_pwd=''
 
   # Define prompts.
   PROMPT='${SSH_TTY:+"%F{9}%n%f%F{7}@%f%F{3}%m%f "}%F{4}${_prompt_sorin_pwd}%(!. %B%F{1}#%f%b.)${editor_info[keymap]} '
-  RPROMPT=''
+  RPROMPT='${editor_info[overwrite]}%(?:: %F{1}⏎%f)${VIM:+" %B%F{6}V%f%b"}${_prompt_sorin_git}'
   SPROMPT='zsh: correct %F{1}%R%f to %F{2}%r%f [nyae]? '
 }