From 31487e73a3ec6d8df0a5a1ad96f6d169d4bf6066 Mon Sep 17 00:00:00 2001
From: Naveen Gogineni <dear.chap@gmail.com>
Date: Sun, 23 Oct 2022 15:56:46 -0400
Subject: [PATCH 1/4] Documentation:(issue_786) Add docs for flag validation

---
 docs/v2/examples/flags.md | 48 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 48 insertions(+)

diff --git a/docs/v2/examples/flags.md b/docs/v2/examples/flags.md
index 873c6ff7e7..fd1f21135a 100644
--- a/docs/v2/examples/flags.md
+++ b/docs/v2/examples/flags.md
@@ -596,3 +596,51 @@ The precedence for flag value sources is as follows (highest to lowest):
 0. Environment variable (if specified)
 0. Configuration file (if specified)
 0. Default defined on the flag
+
+#### Flag Actions
+
+Handlers can be registered per flag which are triggered after a flag has been processed. 
+This can be used for a variety of purposes, one of which is flag validation
+
+<!-- {
+  "args": ["&#45;&#45;port 70000"],
+  "output": "Flag port value 70000 out of range[0-65535]"
+} -->
+```go
+package main
+
+import (
+	"log"
+	"os"
+
+	"github.com/urfave/cli/v2"
+)
+
+func main() {
+	app := &cli.App{
+		Flags: []cli.Flag{
+			&cli.IntFlag{
+				Name:        "port",
+				Usage:       "Use a randomized port",
+				Value:       0,
+				DefaultText: "random",
+				Action: func(ctx *cli.Context, v int) error {
+					if v >= 65536 {
+						return fmt.Errorf("Flag port value %v out of range[0-65535]", v)
+					}
+				},
+			},
+		},
+	}
+
+	if err := app.Run(os.Args); err != nil {
+		log.Fatal(err)
+	}
+}
+```
+
+Will result in help output like:
+
+```
+Flag port value 70000 out of range[0-65535]
+```

From 9d0fdbe28965ff6e530bb1e12950d922631f8c17 Mon Sep 17 00:00:00 2001
From: Naveen Gogineni <dear.chap@gmail.com>
Date: Sun, 23 Oct 2022 16:00:15 -0400
Subject: [PATCH 2/4] Add fmt import

---
 docs/v2/examples/flags.md | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/docs/v2/examples/flags.md b/docs/v2/examples/flags.md
index fd1f21135a..5d817216ec 100644
--- a/docs/v2/examples/flags.md
+++ b/docs/v2/examples/flags.md
@@ -612,6 +612,7 @@ package main
 import (
 	"log"
 	"os"
+	"fmt"
 
 	"github.com/urfave/cli/v2"
 )
@@ -628,6 +629,7 @@ func main() {
 					if v >= 65536 {
 						return fmt.Errorf("Flag port value %v out of range[0-65535]", v)
 					}
+					return nil
 				},
 			},
 		},

From 0dca2d8969c31af7a9890fdde22b85e2b8ba4da9 Mon Sep 17 00:00:00 2001
From: Naveen Gogineni <dear.chap@gmail.com>
Date: Sun, 23 Oct 2022 16:11:30 -0400
Subject: [PATCH 3/4] Add arg

---
 docs/v2/examples/flags.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/docs/v2/examples/flags.md b/docs/v2/examples/flags.md
index 5d817216ec..5beac78174 100644
--- a/docs/v2/examples/flags.md
+++ b/docs/v2/examples/flags.md
@@ -603,7 +603,7 @@ Handlers can be registered per flag which are triggered after a flag has been pr
 This can be used for a variety of purposes, one of which is flag validation
 
 <!-- {
-  "args": ["&#45;&#45;port 70000"],
+  "args": ["&#45;&#45;port","70000"],
   "output": "Flag port value 70000 out of range[0-65535]"
 } -->
 ```go

From de73d1b341292ee628f57da0ffc6a478fb083503 Mon Sep 17 00:00:00 2001
From: dearchap <dear.chap@gmail.com>
Date: Mon, 24 Oct 2022 04:02:15 -0400
Subject: [PATCH 4/4] Update docs/v2/examples/flags.md

Co-authored-by: Dan Buch <dan@meatballhat.com>
---
 docs/v2/examples/flags.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/docs/v2/examples/flags.md b/docs/v2/examples/flags.md
index 5beac78174..eaec6f4a39 100644
--- a/docs/v2/examples/flags.md
+++ b/docs/v2/examples/flags.md
@@ -604,7 +604,7 @@ This can be used for a variety of purposes, one of which is flag validation
 
 <!-- {
   "args": ["&#45;&#45;port","70000"],
-  "output": "Flag port value 70000 out of range[0-65535]"
+  "error": "Flag port value 70000 out of range[0-65535]"
 } -->
 ```go
 package main