feat(helm): cache completion file in the background (#8326)

plugins/helm/helm.plugin.zsh

-# Autocompletion for helm.
-#
-# Copy from kubectl : https://github.com/pstadler
+if (( ! $+commands[helm] )); then
+  return
+fi
+
+# TODO: 2021-12-28: delete this block
+# Remove old generated file
+command rm -f "${ZSH_CACHE_DIR}/helm_completion"
 
-if [ $commands[helm] ]; then
-  source <(helm completion zsh)
+# TODO: 2021-12-28: remove this bit of code as it exists in oh-my-zsh.sh
+# Add completions folder in $ZSH_CACHE_DIR
+command mkdir -p "$ZSH_CACHE_DIR/completions"
+(( ${fpath[(Ie)"$ZSH_CACHE_DIR/completions"]} )) || fpath=("$ZSH_CACHE_DIR/completions" $fpath)
+
+# If the completion file doesn't exist yet, we need to autoload it and
+# bind it to `helm`. Otherwise, compinit will have already done that.
+if [[ ! -f "$ZSH_CACHE_DIR/completions/_helm" ]]; then
+  declare -A _comps
+  autoload -Uz _helm
+  _comps[helm]=_helm
 fi
+
+helm completion zsh >| "$ZSH_CACHE_DIR/completions/_helm" &|