feat(fnm): add autostart option to setup fnm env (#12972)

plugins/fnm/README.md

@@ -2,8 +2,34 @@
 
 This plugin adds autocompletion for [fnm](https://github.com/Schniz/fnm) - a Node.js version manager.
 
-To use it, add `fnm` to the plugins array in your zshrc file:
+To use it, add `fnm` to the plugins array in your `.zshrc` file:
 
 ```zsh
 plugins=(... fnm)
 ```
+
+## Configuration
+
+These settings should go in your `.zshrc` file, before Oh My Zsh is sourced.
+
+### Autostart
+
+If set, the plugin will automatically start fnm for the session, running the `fnm env`:
+
+```zsh
+zstyle ':omz:plugins:fnm' autostart yes
+```
+
+Default: `no` (disabled)
+
+### Use on cd
+
+If set, the Node.js version will be switched based on the requirements of the current directory (recommended):
+
+```zsh
+zstyle ':omz:plugins:fnm' use-on-cd yes
+```
+
+Default: `yes` (enabled)
+
+Check out the [official documentation](https://github.com/Schniz/fnm/blob/master/docs/commands.md) for the available fnm variables.

plugins/fnm/fnm.plugin.zsh

@@ -11,3 +11,11 @@ if [[ ! -f "$ZSH_CACHE_DIR/completions/_fnm" ]]; then
 fi
 
 fnm completions --shell=zsh >| "$ZSH_CACHE_DIR/completions/_fnm" &|
+
+if zstyle -t ':omz:plugins:fnm' autostart; then
+  local -a fnm_env_cmd
+  if zstyle -T ':omz:plugins:fnm' use-on-cd; then
+    fnm_env_cmd+=("--use-on-cd")
+  fi
+  eval "$(fnm env --shell=zsh $fnm_env_cmd)"
+fi