From cdc7af744e07ac8dbb34793f8b392af46ba443f7 Mon Sep 17 00:00:00 2001
From: Lynn Cyrin <lynn@textio.com>
Date: Wed, 17 Jul 2019 00:16:40 -0700
Subject: [PATCH] add handling for multiple required flags

---
 context.go      | 21 ++++++++++++++++++++-
 context_test.go | 23 ++++++++++++++++-------
 2 files changed, 36 insertions(+), 8 deletions(-)

diff --git a/context.go b/context.go
index 8caf90d..383749d 100644
--- a/context.go
+++ b/context.go
@@ -293,13 +293,32 @@ func checkRequiredFlags(flags []Flag, set *flag.FlagSet) error {
 		visited[f.Name] = true
 	})
 
+	var missingFlags []string
 	for _, f := range flags {
 		if rf, ok := f.(RequiredFlag); ok && rf.IsRequired() {
 			key := strings.Split(f.GetName(), ",")[0]
 			if !visited[key] {
-				return fmt.Errorf("Required flag %q not set", f.GetName())
+				missingFlags = append(missingFlags, f.GetName())
 			}
 		}
 	}
+
+	numberOfMissingFlags := len(missingFlags)
+	if numberOfMissingFlags == 1 {
+		return fmt.Errorf("Required flag %q not set", missingFlags[0])
+	}
+	if numberOfMissingFlags >= 2 {
+		var missingFlagsOutput string
+		for idx, f := range missingFlags {
+			// if not the last item, append with a ", "
+			if idx != numberOfMissingFlags-1 {
+				missingFlagsOutput = fmt.Sprintf("%s%s, ", missingFlagsOutput, f)
+			} else {
+				missingFlagsOutput = fmt.Sprintf("%s%s", missingFlagsOutput, f)
+			}
+		}
+		return fmt.Errorf("Required flags %q not set", missingFlagsOutput)
+	}
+
 	return nil
 }
diff --git a/context_test.go b/context_test.go
index fac1d4b..585ca82 100644
--- a/context_test.go
+++ b/context_test.go
@@ -3,6 +3,7 @@ package cli
 import (
 	"flag"
 	"os"
+	"strings"
 	"testing"
 	"time"
 )
@@ -404,10 +405,11 @@ func TestContext_GlobalSet(t *testing.T) {
 
 func TestCheckRequiredFlags(t *testing.T) {
 	tdata := []struct {
-		testCase        string
-		parseInput      []string
-		flags           []Flag
-		expectedAnError bool
+		testCase              string
+		parseInput            []string
+		flags                 []Flag
+		expectedAnError       bool
+		expectedErrorContents []string
 	}{
 		{
 			testCase: "empty",
@@ -423,7 +425,8 @@ func TestCheckRequiredFlags(t *testing.T) {
 			flags: []Flag{
 				StringFlag{Name: "requiredFlag", Required: true},
 			},
-			expectedAnError: true,
+			expectedAnError:       true,
+			expectedErrorContents: []string{"requiredFlag"},
 		},
 		{
 			testCase: "required_and_present",
@@ -460,10 +463,11 @@ func TestCheckRequiredFlags(t *testing.T) {
 		{
 			testCase: "two_required",
 			flags: []Flag{
-				StringFlag{Name: "requiredFlag", Required: true},
+				StringFlag{Name: "requiredFlagOne", Required: true},
 				StringFlag{Name: "requiredFlagTwo", Required: true},
 			},
-			expectedAnError: true,
+			expectedAnError:       true,
+			expectedErrorContents: []string{"requiredFlagOne", "requiredFlagTwo"},
 		},
 		{
 			testCase: "two_required_and_one_present",
@@ -502,6 +506,11 @@ func TestCheckRequiredFlags(t *testing.T) {
 			if !test.expectedAnError && err != nil {
 				t.Errorf("did not expected an error, but there was one: %s", err)
 			}
+			for _, errString := range test.expectedErrorContents {
+				if !strings.Contains(err.Error(), errString) {
+					t.Errorf("expected error %q to contain %q, but it didn't!", err.Error(), errString)
+				}
+			}
 		})
 	}
 }