From e949e84978f2472603bac2a34ad8b0d99da312b8 Mon Sep 17 00:00:00 2001
From: Tim Reddehase <tim.reddehase@xing.com>
Date: Tue, 25 Sep 2018 10:22:55 +0200
Subject: [PATCH] add fish completion basics to cobra.

---
 fish_completions.go | 134 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 134 insertions(+)
 create mode 100644 fish_completions.go

diff --git a/fish_completions.go b/fish_completions.go
new file mode 100644
index 00000000..1eb70441
--- /dev/null
+++ b/fish_completions.go
@@ -0,0 +1,134 @@
+package cobra
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"strings"
+
+	"github.com/spf13/pflag"
+)
+
+// GenFishCompletion generates fish completion and writes to the passed writer.
+func (c *Command) GenFishCompletion(w io.Writer) error {
+	buf := new(bytes.Buffer)
+
+	writeFishPreamble(c, buf)
+	writeFishCommandCompletion(c, c, buf)
+
+	_, err := buf.WriteTo(w)
+	return err
+}
+
+func writeFishPreamble(cmd *Command, buf *bytes.Buffer) {
+	subCommandNames := []string{}
+	rangeCommands(cmd, func(subCmd *Command) {
+		subCommandNames = append(subCommandNames, subCmd.Name())
+	})
+	buf.WriteString(fmt.Sprintf(`
+function __fish_%s_no_subcommand --description 'Test if oly has yet to be given the subcommand'
+	for i in (commandline -opc)
+		if contains -- $i %s
+			return 1
+		end
+	end
+	return 0
+end
+function __fish_%s_has_flag
+  for i in (commandline -opc)
+		if contains -- "--$1" $i
+			return 0
+		end
+	end
+	return 1
+end
+`, cmd.Name(), strings.Join(subCommandNames, " "), cmd.Name()))
+}
+
+func writeFishCommandCompletion(rootCmd, cmd *Command, buf *bytes.Buffer) {
+	rangeCommands(cmd, func(subCmd *Command) {
+		condition := commandCompletionCondition(rootCmd, cmd)
+		buf.WriteString(fmt.Sprintf("complete -c %s -f %s -a %s -d '%s'\n", rootCmd.Name(), condition, subCmd.Name(), subCmd.Short))
+	})
+	writeCommandFlagsCompletion(rootCmd, cmd, buf)
+	rangeCommands(cmd, func(subCmd *Command) {
+		writeFishCommandCompletion(rootCmd, subCmd, buf)
+	})
+}
+
+func writeCommandFlagsCompletion(rootCmd, cmd *Command, buf *bytes.Buffer) {
+	cmd.NonInheritedFlags().VisitAll(func(flag *pflag.Flag) {
+		if nonCompletableFlag(flag) {
+			return
+		}
+		writeCommandFlagCompletion(rootCmd, cmd, buf, flag)
+	})
+	cmd.InheritedFlags().VisitAll(func(flag *pflag.Flag) {
+		if nonCompletableFlag(flag) {
+			return
+		}
+		writeCommandFlagCompletion(rootCmd, cmd, buf, flag)
+	})
+}
+
+func writeCommandFlagCompletion(rootCmd, cmd *Command, buf *bytes.Buffer, flag *pflag.Flag) {
+	shortHandPortion := ""
+	if len(flag.Shorthand) > 0 {
+		shortHandPortion = fmt.Sprintf("-s %s", flag.Shorthand)
+	}
+	condition := completionCondition(rootCmd, cmd)
+	buf.WriteString(fmt.Sprintf("complete -c %s -f %s %s %s -l %s -d '%s'\n",
+		rootCmd.Name(), condition, flagRequiresArgumentCompletion(flag), shortHandPortion, flag.Name, flag.Usage))
+}
+
+func flagRequiresArgumentCompletion(flag *pflag.Flag) string {
+	if flag.Value.Type() != "bool" {
+		return "-r"
+	}
+	return ""
+}
+
+func subCommandPath(rootCmd *Command, cmd *Command) string {
+	path := []string{}
+	currentCmd := cmd
+	for {
+		path = append([]string{currentCmd.Name()}, path...)
+		if currentCmd.Parent() == rootCmd {
+			return strings.Join(path, " ")
+		}
+		currentCmd = currentCmd.Parent()
+	}
+	return ""
+}
+
+func rangeCommands(cmd *Command, callback func(subCmd *Command)) {
+	for _, subCmd := range cmd.Commands() {
+		// TODO: for merging to cobra: add || subCmd == cmd.helpCommand
+		if !subCmd.IsAvailableCommand() {
+			continue
+		}
+		callback(subCmd)
+	}
+}
+
+func commandCompletionCondition(rootCmd, cmd *Command) string {
+	localNonPersistentFlags := cmd.LocalNonPersistentFlags()
+	bareConditions := []string{}
+	if rootCmd != cmd {
+		bareConditions = append(bareConditions, fmt.Sprintf("__fish_seen_subcommand_from %s", subCommandPath(rootCmd, cmd)))
+	} else {
+		bareConditions = append(bareConditions, fmt.Sprintf("__fish_%s_no_subcommand", rootCmd.Name()))
+	}
+	localNonPersistentFlags.VisitAll(func(flag *pflag.Flag) {
+		bareConditions = append(bareConditions, fmt.Sprintf("not __fish_%s_has_flag %s", rootCmd.Name(), flag.Name))
+	})
+	return fmt.Sprintf("-n '%s'", strings.Join(bareConditions, "; and "))
+}
+
+func completionCondition(rootCmd, cmd *Command) string {
+	condition := fmt.Sprintf("-n '__fish_%s_no_subcommand'", rootCmd.Name())
+	if rootCmd != cmd {
+		condition = fmt.Sprintf("-n '__fish_seen_subcommand_from %s'", subCommandPath(rootCmd, cmd))
+	}
+	return condition
+}