From 3064887ba769f9a62c0383ca86c99a9fe8bc0f73 Mon Sep 17 00:00:00 2001
From: Bittrance <bittrance@gmail.com>
Date: Fri, 23 May 2025 23:08:56 +0200
Subject: [PATCH] Fish completion now supports dynamic completions.

---
 command_setup.go                 |  5 -----
 command_test.go                  | 34 ++++++++++++++++++++++++++++++++
 fish.go                          | 15 +++++++++++++-
 help.go                          |  3 +++
 testdata/expected-fish-full.fish |  4 +++-
 5 files changed, 54 insertions(+), 7 deletions(-)

diff --git a/command_setup.go b/command_setup.go
index 09df4a3084..b8b32184eb 100644
--- a/command_setup.go
+++ b/command_setup.go
@@ -19,11 +19,6 @@ func (cmd *Command) setupDefaults(osArgs []string) {
 	isRoot := cmd.parent == nil
 	tracef("isRoot? %[1]v (cmd=%[2]q)", isRoot, cmd.Name)
 
-	if cmd.ShellComplete == nil {
-		tracef("setting default ShellComplete (cmd=%[1]q)", cmd.Name)
-		cmd.ShellComplete = DefaultCompleteWithFlags
-	}
-
 	if cmd.Name == "" && isRoot {
 		name := filepath.Base(osArgs[0])
 		tracef("setting cmd.Name from first arg basename (cmd=%[1]q)", name)
diff --git a/command_test.go b/command_test.go
index f88fea9d05..7aa37a1cc0 100644
--- a/command_test.go
+++ b/command_test.go
@@ -95,6 +95,10 @@ func buildExtendedTestCommand() *Command {
 		Usage:   "retrieve generic information",
 	}, {
 		Name: "some-command",
+	}, {
+		Name:          "custom",
+		ShellComplete: func(ctx context.Context, c *Command) {},
+		HideHelp:      true,
 	}, {
 		Name:   "hidden-command",
 		Hidden: true,
@@ -4870,6 +4874,36 @@ func TestJSONExportCommand(t *testing.T) {
 			"arguments": null,
 			"readArgsFromStdin": false
 		  },
+		  {
+			"name": "custom",
+			"aliases": null,
+			"usage": "",
+			"usageText": "",
+			"argsUsage": "",
+			"version": "",
+			"description": "",
+			"defaultCommand": "",
+			"category": "",
+			"commands": null,
+			"flags": null,
+			"hideHelp": true,
+			"hideHelpCommand": false,
+			"hideVersion": false,
+			"hidden": false,
+			"authors": null,
+			"copyright": "",
+			"metadata": null,
+			"sliceFlagSeparator": "",
+			"disableSliceFlagSeparator": false,
+			"useShortOptionHandling": false,
+			"suggest": false,
+			"allowExtFlags": false,
+			"skipFlagParsing": false,
+			"prefixMatchCommands": false,
+			"mutuallyExclusiveFlags": null,
+			"arguments": null,
+			"readArgsFromStdin": false
+		  },
 		  {
 			"name": "hidden-command",
 			"aliases": null,
diff --git a/fish.go b/fish.go
index 320dfc6c69..b731b28456 100644
--- a/fish.go
+++ b/fish.go
@@ -53,8 +53,21 @@ func (cmd *Command) writeFishCompletionTemplate(w io.Writer) error {
 }
 
 func prepareFishCommands(binary string, parent *Command) []string {
-	commands := parent.Commands
 	completions := []string{}
+	if parent.ShellComplete != nil {
+		var completion strings.Builder
+		fmt.Fprintf(&completion,
+			"complete -x -c %s -n '%s' -a '%s'",
+			binary,
+			commandAncestry(parent),
+			"(eval command (commandline -pc) "+completionFlag+")",
+		)
+		completions = append(
+			completions,
+			completion.String(),
+		)
+	}
+	commands := parent.Commands
 	for _, command := range commands {
 		if !command.Hidden {
 			var completion strings.Builder
diff --git a/help.go b/help.go
index c039a5d02b..2ffe83b422 100644
--- a/help.go
+++ b/help.go
@@ -502,6 +502,9 @@ func checkCompletions(ctx context.Context, cmd *Command) bool {
 	if cmd.ShellComplete != nil {
 		tracef("running shell completion func for command %[1]q", cmd.Name)
 		cmd.ShellComplete(ctx, cmd)
+	} else {
+		tracef("running default shell completion func for command %[1]q", cmd.Name)
+		DefaultCompleteWithFlags(ctx, cmd)
 	}
 
 	return true
diff --git a/testdata/expected-fish-full.fish b/testdata/expected-fish-full.fish
index b69e8e51d5..cff2ffceac 100644
--- a/testdata/expected-fish-full.fish
+++ b/testdata/expected-fish-full.fish
@@ -2,7 +2,7 @@
 
 function __fish_greet_no_subcommand --description 'Test if there has been any subcommand yet'
     for i in (commandline -opc)
-        if contains -- $i config c info i in some-command hidden-command usage u
+        if contains -- $i config c info i in some-command custom hidden-command usage u
             return 1
         end
     end
@@ -30,6 +30,8 @@ complete -x -c greet -n '__fish_seen_subcommand_from info i in; and not __fish_s
 complete -x -c greet -n '__fish_greet_no_subcommand' -a 'some-command'
 complete -c greet -n '__fish_seen_subcommand_from some-command' -f -l help -s h -d 'show help'
 complete -x -c greet -n '__fish_seen_subcommand_from some-command; and not __fish_seen_subcommand_from help h' -a 'help' -d 'Shows a list of commands or help for one command'
+complete -x -c greet -n '__fish_greet_no_subcommand' -a 'custom'
+complete -x -c greet -n '__fish_seen_subcommand_from custom' -a '(eval command (commandline -pc) --generate-shell-completion)'
 complete -c greet -n '__fish_seen_subcommand_from hidden-command' -f -l completable
 complete -c greet -n '__fish_seen_subcommand_from hidden-command' -f -l help -s h -d 'show help'
 complete -x -c greet -n '__fish_seen_subcommand_from hidden-command; and not __fish_seen_subcommand_from help h' -a 'help' -d 'Shows a list of commands or help for one command'