nvm: add autoloading of nvm version in .nvmrc

Closes #5782
Fixes #8959
Closes #8976

plugins/nvm/README.md

@@ -20,3 +20,7 @@ plugins=(... nvm)
 - **`NVM_LAZY`**: if you want the plugin to defer the load of nvm to speed-up the start of your zsh session,
   set `NVM_LAZY` to `1`. This will use the `--no-use` parameter when loading nvm, and will create a function
   for `node`, `npm` and `yarn`, so when you call either of these three, nvm will load with `nvm use default`.
+
+- **`NVM_AUTOLOAD`**: if `NVM_AUTOLOAD` is set to `1`, the plugin will automatically load a node version when
+  if finds a [`.nvmrc` file](https://github.com/nvm-sh/nvm#nvmrc) in the current working directory indicating
+  which node version to load.

plugins/nvm/nvm.plugin.zsh

@@ -35,6 +35,33 @@ if (( $+NVM_LAZY )); then
   }
 fi
 
+# Autoload nvm when finding a .nvmrc file in the current directory
+# Adapted from: https://github.com/nvm-sh/nvm#zsh
+if (( $+NVM_AUTOLOAD )); then
+  load-nvmrc() {
+    local node_version="$(nvm version)"
+    local nvmrc_path="$(nvm_find_nvmrc)"
+
+    if [[ -n "$nvmrc_path" ]]; then
+      local nvmrc_node_version=$(nvm version "$(cat "${nvmrc_path}")")
+
+      if [[ "$nvmrc_node_version" = "N/A" ]]; then
+        nvm install
+      elif [[ "$nvmrc_node_version" != "$node_version" ]]; then
+        nvm use
+      fi
+    elif [[ "$node_version" != "$(nvm version default)" ]]; then
+      echo "Reverting to nvm default version"
+      nvm use default
+    fi
+  }
+
+  autoload -U add-zsh-hook
+  add-zsh-hook chpwd load-nvmrc
+
+  load-nvmrc
+fi
+
 # Load nvm bash completion
 for nvm_completion in "$NVM_DIR/bash_completion" "$NVM_HOMEBREW/etc/bash_completion.d/nvm"; do
   if [[ -f "$nvm_completion" ]]; then
@@ -47,4 +74,4 @@ for nvm_completion in "$NVM_DIR/bash_completion" "$NVM_HOMEBREW/etc/bash_complet
   fi
 done
 
-unset NVM_HOMEBREW NVM_LAZY nvm_completion
+unset NVM_HOMEBREW NVM_LAZY NVM_AUTOLOAD nvm_completion