zsh-native asdf completion setup

Add a zsh-native completion system function for `asdf`.

I too often hit snags with bash completions in zsh, so I bias strongly
towards zsh-native completions.

This needs to end up in `$fpath` with a filename of `_asdf` but it
seemed unfriendly to use that name in this repo, so call it `_asdf.zsh`
and document a symlink.  Mark the file as executable to be compatible
with one convention of "personal functions should only autoload if
executable" (but that's probably so historic that very few people still
use it; I'm one of them, though).

completions/_asdf.zsh

@@ -0,0 +1,143 @@
+#compdef asdf
+#description tool to manage versions of multiple runtimes
+
+local curcontext="$curcontext" state state_descr line subcmd
+local asdf_dir="${ASDF_DATA_DIR:-$HOME/.asdf}"
+
+local -a asdf_commands
+asdf_commands=( # 'asdf help' lists commands with help text
+  'plugin-add:add plugin from asdf-plugins repo or from git URL'
+  'plugin-list:list installed plugins (--url with URLs)'
+  'plugin-list-all:list all plugins registered in asdf-plugins repo'
+  'plugin-remove:remove named plugin and all packages for it'
+  'plugin-update:update named plugin (or --all)'
+  'install:install plugin at stated version, or all from .tools-versions'
+  'uninstall:remove a specific version of a package'
+  'current:display current versions for named package (else all)'
+  'where:display install path for given package at optional specified version'
+  'which:display path to an executable'
+  'shell:via env vars, set package to version in current shell'
+  'local:set package local version'
+  'global:set package global version'
+  'list:list installed versions of a package'
+  'list-all:list all available (remote) versions of a package'
+  'exec:executes the command shim for the current version'
+  'env:prints or runs an executable under a command environment'
+  'reshim:recreate shims for version of a package'
+  'shim-versions:list for given command which plugins and versions provide it'
+  'update:update ASDF to the latest stable release (unless --head)'
+)
+
+_asdf__available_plugins() {
+  local plugin_dir="${asdf_dir:?}/repository/plugins"
+  if [[ ! -d "$plugin_dir" ]]; then
+    _wanted asdf-available-plugins expl 'ASDF Installable Plugins' \
+      compadd -x "no plugins repository found"
+    return
+  fi
+  local -a plugins
+  plugins=( "$plugin_dir"/*(:t) )
+  _wanted asdf-available-plugins expl 'ASDF Installable Plugins' \
+    compadd -a plugins
+}
+
+_asdf__installed_plugins() {
+  local plugin_dir="${asdf_dir:?}/plugins"
+  if [[ ! -d "$plugin_dir" ]]; then
+    _wanted asdf-plugins expl 'ASDF Plugins' \
+      compadd -x "no plugins dir, none installed yet"
+    return
+  fi
+  local -a plugins
+  plugins=( "$plugin_dir"/*(:t) )
+  _wanted asdf-plugins expl 'ASDF Plugins' \
+    compadd -a plugins
+}
+
+_asdf__installed_versions_of() {
+  local plugin_dir="${asdf_dir:?}/installs/${1:?need a plugin version}"
+  if [[ ! -d "$plugin_dir" ]]; then
+    _wanted "asdf-versions-$1" expl "ASDF Plugin ${(q-)1} versions" \
+      compadd -x "no versions installed"
+    return
+  fi
+  local -a versions
+  versions=( "$plugin_dir"/*(:t) )
+  _wanted "asdf-versions-$1" expl "ASDF Plugin ${(q-)1} versions" \
+    compadd -a versions
+}
+
+if (( CURRENT == 2 )); then
+  _arguments -C : '--version[version]' ':command:->command'
+fi
+
+case "$state" in
+(command)
+  _describe -t asdf-commands 'ASDF Commands' asdf_commands
+  return
+  ;;
+esac
+subcmd="${words[2]}"
+curcontext="${curcontext%:*}=$subcmd:"
+
+case "$subcmd" in
+(plugin-add)
+  if (( CURRENT == 3 )); then
+    _asdf__available_plugins
+  else
+    # Optional URL
+    curcontext="${curcontext/=plugin-add:/=plugin-add-${words[3]}:}"
+    if (( CURRENT == 4 )); then
+      _arguments "*:${words[3]} package url:_urls"
+    fi
+  fi
+  ;;
+(plugin-remove|current|list|list-all)
+  (( CURRENT == 3 )) && _asdf__installed_plugins
+  ;;
+(plugin-update)
+  (( CURRENT == 3 )) && _alternative \
+    'all:all:(--all)' \
+    'asdf-available-plugins:Installed ASDF Plugins:_asdf__installed_plugins'
+  ;;
+(install)
+  if (( CURRENT == 3 )); then
+    _asdf__installed_plugins
+  elif (( CURRENT == 4 )); then
+    _wanted "remote-versions-${words[3]}" \
+      expl "Available versions of ${words[3]}" \
+      compadd -- $(asdf list-all "${words[3]}")
+  fi
+  ;;
+(uninstall|where|shell|local|global)
+  if (( CURRENT == 3 )); then
+    _asdf__installed_plugins
+  elif (( CURRENT == 4 )); then
+    _asdf__installed_versions_of "${words[3]}"
+  fi
+  ;;
+(which|shim-versions)
+  _wanted asdf-shims expl "ASDF Shims" compadd -- "${asdf_dir:?}/shims"/*(:t)
+  ;;
+(exec)
+  # asdf exec <shim-cmd> [<shim-cmd args ...>]
+  if (( CURRENT == 3 )); then
+    _wanted asdf-shims expl "ASDF Shims" compadd -- "${asdf_dir:?}/shims"/*(:t)
+  else
+    compset -n 3
+    _normal -p "asdf-shims-${words[3]}"
+  fi
+  ;;
+(env)
+  # asdf exec <shim-name> <arbitrary-cmd> [<cmd args ...>]
+  if (( CURRENT == 3 )); then
+    _wanted asdf-shims expl "ASDF Shims" compadd -- "${asdf_dir:?}/shims"/*(:t)
+  else
+    compset -n 4
+    _normal -p "asdf-shims-${words[3]}"
+  fi
+  ;;
+(update)
+  (( CURRENT == 3 )) && compadd -- --head
+  ;;
+esac

docs/core-manage-asdf-vm.md

@@ -105,6 +105,14 @@ the ones above.
 autoload -Uz compinit && compinit
 ```
 
+If you have a function path set up and have a place to put a custom completion
+file, then instead of adding a source of `asdf.bash` to your `.zshrc`, you can
+instead:
+
+```shell
+ln -s ~/.asdf/completions/_asdf.zsh ${fpath[1]}/_asdf
+```
+
 #### ** Fish **
 
 Installation via **Git**: