Re: [PATCH] Add customizable `vcs` prompt theme (was Re: [RFC][PATCH] `newuser` prompt theme)

[Marlon Richert <marlon.richert@xxxxxxxxx>]

On Wed, Jun 9, 2021 at 4:22 PM Roman Perepelitsa
<roman.perepelitsa@xxxxxxxxx> wrote:
>
> A few questions/comments after a cursory look.
>
> Why is prompt_vcs_chpwd using exec + read instead of $(...)?

Because I apparently forgot that $(...) runs in a subshell, too. ^_^;

> Why hook zle-line-init instead of precmd? There is a comment saying
> that it's "so you can press Enter on an empty line to update VCS info"
> but I don't understand it. When I press Enter in zle with an empty
> buffer, precmd does get called.

I could've sworn that precmd doesn't get called under those
conditions, but I guess I confused it with preexec.

> There is a race that may cause incorrect git status to be displayed.
> For example, suppose I run these commands in quick succession in a
> large git repository:
>
>     git checkout -b foo
>     git checkout -b bar
>
> If the two background vcs processes finish out of order, prompt will
> incorrectly display "foo" when the current branch is "bar". This error
> will persist until another command (perhaps empty) is executed.
>
> Pressing and holding Enter in a large repository may cause large (and
> unbounded) strain on the machine.

Thanks for the review! Here's a new version of the patch that
hopefully addresses the concerns you raised.

From 41ffe718d7d58411254dc35f9618ae4fb0906aa6 Mon Sep 17 00:00:00 2001
From: Marlon Richert <marlon.richert@xxxxxxxxx>
Date: Wed, 9 Jun 2021 15:53:47 +0300
Subject: [PATCH] Add customizable `vcs` prompt theme

---
 Functions/Prompts/prompt_vcs_setup | 180 +++++++++++++++++++++++++++++
 1 file changed, 180 insertions(+)
 create mode 100644 Functions/Prompts/prompt_vcs_setup

diff --git a/Functions/Prompts/prompt_vcs_setup b/Functions/Prompts/prompt_vcs_setup
new file mode 100644
index 000000000..8adc7c04d
--- /dev/null
+++ b/Functions/Prompts/prompt_vcs_setup
@@ -0,0 +1,180 @@
+##
+# Prompt that can be customized through vcs_info
+#
+
+autoload -Uz add-zsh-hook vcs_info
+
+# Prompt segments
+readonly -gHA _prompt_vcs_ps1=(
+    chpwd     $'\n%B%F{blue}%~%%b%f/'
+    left      $'%%(?,%F{green},%F{red})%#%%b%f%%s '
+    right     '%B%F{blue}%n%b%f%k@%F{magenta}%m%f'
+    staged    '%B%F{green}+%b%f'
+    unstaged  '%B%F{red}*%b%f'
+    action    '%B%F{red}%a%%b%f'
+    branch    '%B%F{cyan}%b%%b%f'
+    repo      '|%B%F{blue}%r%%b%f'
+)
+
+prompt_vcs_help() {
+  print -r -- \
+"This prompt theme can by customized by copy-pasting any of the code below to
+your .zshrc file and editing it there:
+
+  # For each of the following three entries:
+  #   1st string is printed after changing dirs.
+  #   2nd string is the left prompt.
+  #   3rd string is the right prompt and updated asynchronously.
+
+  # Normal prompt:
+  zstyle ':vcs_info:*:prompt_vcs:*' nvcsformats \\
+      "${(q+)_prompt_vcs_ps1[chpwd]//'%%'/%}" \\
+      "${(q+)_prompt_vcs_ps1[left]//'%%'/%}" \\
+      "${(q+)_prompt_vcs_ps1[right]//'%%'/%}"
+
+  # Prompt inside VCS repo:
+  zstyle ':vcs_info:*:prompt_vcs:*' formats \\
+      ${(q+)_prompt_vcs_ps1[chpwd]} \\
+      ${(q+)_prompt_vcs_ps1[left]} \\
+      ${(q+):-%u%c$_prompt_vcs_ps1[branch]$_prompt_vcs_ps1[repo]}
+
+  # Prompt during an ongoing VCS action:
+  zstyle ':vcs_info:*:prompt_vcs:*' actionformats \\
+      ${(q+)_prompt_vcs_ps1[chpwd]} \\
+      ${(q+)_prompt_vcs_ps1[left]} \\
+      ${(q+):-%u%c$_prompt_vcs_ps1[action]$_prompt_vcs_ps1[repo]}
+
+  # These set the values of %c and %u, respectively:
+  zstyle ':vcs_info:*:prompt_vcs:*' stagedstr ${(q+)_prompt_vcs_ps1[staged]}
+  zstyle ':vcs_info:*:prompt_vcs:*' unstagedstr ${(q+)_prompt_vcs_ps1[unstaged]}
+
+For more info on the settings above, see
+http://zsh.sourceforge.net/Doc/Release/Prompt-Expansion.html and the end of
+http://zsh.sourceforge.net/Doc/Release/User-Contributions.html#vcs_005finfo-Configuration";
+}
+
+# Sets a style if it hasn't been set yet.
+_prompt_vcs_zstyle() {
+  local -a val
+  zstyle -g val "$1" "$2"
+  (( $#val )) ||
+      zstyle "$@"
+}
+
+_prompt_vcs_info() {
+  _prompt_vcs_zstyle ':vcs_info:*:prompt_vcs:*' max-exports 3 # Default is 2.
+
+  _prompt_vcs_zstyle ':vcs_info:*:prompt_vcs:*' nvcsformats \
+      "${_prompt_vcs_ps1[chpwd]//'%%'/%}" \
+      "${_prompt_vcs_ps1[left]//'%%'/%}" \
+      "${_prompt_vcs_ps1[right]//'%%'/%}"
+  _prompt_vcs_zstyle ':vcs_info:*:prompt_vcs:*' formats \
+      "$_prompt_vcs_ps1[chpwd]" \
+      "$_prompt_vcs_ps1[left]" \
+      "%u%c$_prompt_vcs_ps1[branch]$_prompt_vcs_ps1[repo]"
+  _prompt_vcs_zstyle ':vcs_info:*:prompt_vcs:*' actionformats \
+      "$_prompt_vcs_ps1[chpwd]" \
+      "$_prompt_vcs_ps1[left]" \
+      "%u%c$_prompt_vcs_ps1[action]$_prompt_vcs_ps1[repo]"
+  _prompt_vcs_zstyle ':vcs_info:*:prompt_vcs:*' stagedstr \
+      "$_prompt_vcs_ps1[staged]"
+  _prompt_vcs_zstyle ':vcs_info:*:prompt_vcs:*' unstagedstr \
+      "$_prompt_vcs_ps1[unstaged]"
+
+  vcs_info prompt_vcs # Call with namespace.
+
+  print -rNC1 -- \
+      "${(q+)vcs_info_msg_0_}" "${(q+)vcs_info_msg_1_}" "${(q+)vcs_info_msg_2_}"
+}
+
+prompt_vcs_chpwd() {
+  emulate -L zsh
+
+  # Don't check for changes at this point, for performance reasons.
+  typeset -ga _prompt_vcs_info_msg_=( "${(0@Q)$(
+    _prompt_vcs_zstyle ':vcs_info:*:prompt_vcs:*' check-for-changes no
+    _prompt_vcs_zstyle ':vcs_info:*:prompt_vcs:*' check-for-staged-changes no
+    _prompt_vcs_info
+  )}" )
+  shift -p _prompt_vcs_info_msg_
+  print -Pr -- "$_prompt_vcs_info_msg_[1]"
+  PS1="$_prompt_vcs_info_msg_[2]"
+  RPS1="$_prompt_vcs_info_msg_[3]"
+}
+
+prompt_vcs_precmd() {
+  emulate -L zsh
+
+  # Kill any unfinished process before starting a new one.
+  if [[ -n $prompt_vcs_fd ]] && { : <&$prompt_vcs_fd } 2>/dev/null; then
+    zle -F "$prompt_vcs_fd" 2> /dev/null
+    exec {prompt_vcs_fd}<&-
+  fi
+
+  # Asynchronously check for changes.
+  typeset -gH prompt_vcs_fd=
+  exec {prompt_vcs_fd}< <(
+    _prompt_vcs_zstyle ':vcs_info:*:prompt_vcs:*' check-for-changes yes
+    _prompt_vcs_zstyle ':vcs_info:*:prompt_vcs:*' check-for-staged-changes yes
+    _prompt_vcs_info
+    print -r -- "$PWD"
+  )
+
+  # Add callback. Needs to be a widget, so we can refresh the prompt.
+  zle -Fw "$prompt_vcs_fd" prompt_vcs_fd-widget
+}
+
+# Callback widget function for our async fetch of VCS changes
+prompt_vcs_fd-widget() {
+  emulate -L zsh
+
+  [[ -n $1 ]] ||
+      return  # Don't accidentally close fd 0.
+  {
+    local -i fd=$1
+    zle -F "$fd"  # Detach ourselves, so we don't get called more than once.
+
+    [[ -z $2 ]] ||
+        return  # Error occured.
+
+    local -a reply
+    IFS=$'\0' read -Aru "$fd"
+  } always {
+    exec {fd}<&-
+  }
+  [[ $reply[-1] == $PWD ]] ||
+      return  # Info is not for current dir.
+
+  shift -p reply
+  typeset -ga _prompt_vcs_info_msg_=( "${(@Q)reply}" )
+  RPS1="$_prompt_vcs_info_msg_[3]"
+  zle .reset-prompt
+}
+
+prompt_vcs_setup() {
+  prompt_opts=( cr percent sp ) # Tell promptinit which options to set.
+
+  # Indent left continuation prompt for each open shell construct.
+  local -a indent=( '%('{1..36}'_,  ,)' )
+  PS2="${(j::)indent}"
+
+  RPS2='%F{yellow}# %^%f'
+  PS4=$'#->%(?,%F{green},%B%F{red}%S)%?%b%f%s\t%e+%F{green}%1N%f:%I  %(1_,%F{yellow}%K{black}%_%f%k ,)'
+  SPROMPT='Correct %B%F{red}%U%R%b%f%u to %B%F{green}%r%b%f? [%Sy%ses|%Sn%so|%Se%sdit|%Sa%sbort] '
+  PROMPT_EOL_MARK='%S%F{cyan}%#%s%f'
+  zle_highlight=(
+      isearch:fg=black,bg=yellow
+      special:fg=cyan,bold
+      region:fg=white,bg=blue,bold
+      suffix:fg=white,bg=blue,bold
+      paste:bold
+  )
+
+  add-zsh-hook chpwd  prompt_vcs_chpwd
+  add-zsh-hook precmd prompt_vcs_precmd
+  zle -N prompt_vcs_fd-widget # Callback widget for async VCS update.
+
+  prompt_vcs_chpwd
+}
+
+prompt_vcs_setup "$@"
-- 
2.30.1 (Apple Git-130)