Use native zsh completion script generator

So far, Skaffold used a wrapper code borrowed from kubectl to use the bash completion script for zsh. Cobra v0.0.5 introduced a native completion script generator for zsh. To support the `source <(...)` use-case, a minor tweak is necessary (also see spf13/cobra#887)

Signed-off-by: Cornelius Weig <22861411+corneliusweig@users.noreply.github.com>

cmd/skaffold/app/cmd/completion.go

@@ -14,30 +14,9 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-/*
-NOTICE: The zsh wrapper code below is derived from the completion code
-in kubectl (k8s.io/kubernetes/pkg/kubectl/cmd/completion/completion.go),
-with the following license:
-
-Copyright 2016 The Kubernetes Authors.
-
-Licensed under the Apache License, Version 2.0 (the "License");
-you may not use this file except in compliance with the License.
-You may obtain a copy of the License at
-
-    http://www.apache.org/licenses/LICENSE-2.0
-
-Unless required by applicable law or agreed to in writing, software
-distributed under the License is distributed on an "AS IS" BASIS,
-WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-See the License for the specific language governing permissions and
-limitations under the License.
-*/
-
 package cmd
 
 import (
-	"bytes"
 	"fmt"
 	"io"
 	"os"
@@ -65,157 +44,7 @@ const (
 	Additionally, you may want to output the completion to a file and source in your .bashrc
 `
 
-	zshInitialization = `#compdef skaffold
-
-__skaffold_bash_source() {
-	alias shopt=':'
-	alias _expand=_bash_expand
-	alias _complete=_bash_comp
-	emulate -L sh
-	setopt kshglob noshglob braceexpand
-
-	source "$@"
-}
-
-__skaffold_type() {
-	# -t is not supported by zsh
-	if [ "$1" == "-t" ]; then
-		shift
-
-		# fake Bash 4 to disable "complete -o nospace". Instead
-		# "compopt +-o nospace" is used in the code to toggle trailing
-		# spaces. We don't support that, but leave trailing spaces on
-		# all the time
-		if [ "$1" = "__skaffold_compopt" ]; then
-			echo builtin
-			return 0
-		fi
-	fi
-	type "$@"
-}
-
-__skaffold_compgen() {
-	local completions w
-	completions=( $(compgen "$@") ) || return $?
-
-	# filter by given word as prefix
-	while [[ "$1" = -* && "$1" != -- ]]; do
-		shift
-		shift
-	done
-	if [[ "$1" == -- ]]; then
-		shift
-	fi
-	for w in "${completions[@]}"; do
-		if [[ "${w}" = "$1"* ]]; then
-			echo "${w}"
-		fi
-	done
-}
-
-__skaffold_compopt() {
-	true # don't do anything. Not supported by bashcompinit in zsh
-}
-
-__skaffold_ltrim_colon_completions()
-{
-	if [[ "$1" == *:* && "$COMP_WORDBREAKS" == *:* ]]; then
-		# Remove colon-word prefix from COMPREPLY items
-		local colon_word=${1%${1##*:}}
-		local i=${#COMPREPLY[*]}
-		while [[ $((--i)) -ge 0 ]]; do
-			COMPREPLY[$i]=${COMPREPLY[$i]#"$colon_word"}
-		done
-	fi
-}
-
-__skaffold_get_comp_words_by_ref() {
-	cur="${COMP_WORDS[COMP_CWORD]}"
-	prev="${COMP_WORDS[${COMP_CWORD}-1]}"
-	words=("${COMP_WORDS[@]}")
-	cword=("${COMP_CWORD[@]}")
-}
-
-__skaffold_filedir() {
-	local RET OLD_IFS w qw
-
-	__skaffold_debug "_filedir $@ cur=$cur"
-	if [[ "$1" = \~* ]]; then
-		# somehow does not work. Maybe, zsh does not call this at all
-		eval echo "$1"
-		return 0
-	fi
-
-	OLD_IFS="$IFS"
-	IFS=$'\n'
-	if [ "$1" = "-d" ]; then
-		shift
-		RET=( $(compgen -d) )
-	else
-		RET=( $(compgen -f) )
-	fi
-	IFS="$OLD_IFS"
-
-	IFS="," __skaffold_debug "RET=${RET[@]} len=${#RET[@]}"
-
-	for w in ${RET[@]}; do
-		if [[ ! "${w}" = "${cur}"* ]]; then
-			continue
-		fi
-		if eval "[[ \"\${w}\" = *.$1 || -d \"\${w}\" ]]"; then
-			qw="$(__skaffold_quote "${w}")"
-			if [ -d "${w}" ]; then
-				COMPREPLY+=("${qw}/")
-			else
-				COMPREPLY+=("${qw}")
-			fi
-		fi
-	done
-}
-
-__skaffold_quote() {
-    if [[ $1 == \'* || $1 == \"* ]]; then
-        # Leave out first character
-        printf %q "${1:1}"
-    else
-	printf %q "$1"
-    fi
-}
-
-autoload -U +X bashcompinit && bashcompinit
-
-# use word boundary patterns for BSD or GNU sed
-LWORD='[[:<:]]'
-RWORD='[[:>:]]'
-if sed --help 2>&1 | grep -q GNU; then
-	LWORD='\<'
-	RWORD='\>'
-fi
-
-__skaffold_convert_bash_to_zsh() {
-	sed \
-	-e 's/declare -F/whence -w/' \
-	-e 's/_get_comp_words_by_ref "\$@"/_get_comp_words_by_ref "\$*"/' \
-	-e 's/local \([a-zA-Z0-9_]*\)=/local \1; \1=/' \
-	-e 's/flags+=("\(--.*\)=")/flags+=("\1"); two_word_flags+=("\1")/' \
-	-e 's/must_have_one_flag+=("\(--.*\)=")/must_have_one_flag+=("\1")/' \
-	-e "s/${LWORD}_filedir${RWORD}/__skaffold_filedir/g" \
-	-e "s/${LWORD}_get_comp_words_by_ref${RWORD}/__skaffold_get_comp_words_by_ref/g" \
-	-e "s/${LWORD}__ltrim_colon_completions${RWORD}/__skaffold_ltrim_colon_completions/g" \
-	-e "s/${LWORD}compgen${RWORD}/__skaffold_compgen/g" \
-	-e "s/${LWORD}compopt${RWORD}/__skaffold_compopt/g" \
-	-e "s/${LWORD}declare${RWORD}/builtin declare/g" \
-	-e "s/\\\$(type${RWORD}/\$(__skaffold_type/g" \
-	<<'BASH_COMPLETION_EOF'
-`
-
-	zshTail = `
-BASH_COMPLETION_EOF
-}
-
-__skaffold_bash_source <(__skaffold_convert_bash_to_zsh)
-_complete skaffold 2>/dev/null
-`
+	zshCompdef = "\ncompdef _skaffold skaffold\n"
 )
 
 func completion(cmd *cobra.Command, args []string) {
@@ -245,11 +74,8 @@ func NewCmdCompletion() *cobra.Command {
 }
 
 func runCompletionZsh(cmd *cobra.Command, out io.Writer) {
-	io.WriteString(out, zshInitialization)
-	buf := new(bytes.Buffer)
-	rootCmd(cmd).GenBashCompletion(buf)
-	out.Write(buf.Bytes())
-	io.WriteString(out, zshTail)
+	_ = rootCmd(cmd).GenZshCompletion(out)
+	_, _ = io.WriteString(out, zshCompdef)
 }
 
 func rootCmd(cmd *cobra.Command) *cobra.Command {