From cdbff761b6878ce921c4d27671d2c7eec5c8eaaa Mon Sep 17 00:00:00 2001
From: Vladislav Mitov <vladislav.mitov@gmail.com>
Date: Thu, 5 Apr 2018 19:30:37 +0300
Subject: [PATCH] Allow duplicate keys in sources

When same key appear multiple times in sources, casper will merge them
in array. That way you can construct arrays in the command line.
---
 source/multi.go      | 18 +++++++++++++++---
 source/multi_test.go | 10 ++++++++--
 2 files changed, 23 insertions(+), 5 deletions(-)

diff --git a/source/multi.go b/source/multi.go
index 054fae1..f291d1c 100644
--- a/source/multi.go
+++ b/source/multi.go
@@ -1,6 +1,8 @@
 package source
 
-import "fmt"
+import (
+	"fmt"
+)
 
 // NewMultiSourcer create source that is a collection of value sources.
 func NewMultiSourcer(vss ...Getter) (*Source, error) {
@@ -8,8 +10,18 @@ func NewMultiSourcer(vss ...Getter) (*Source, error) {
 
 	for _, s := range vss {
 		for k, v := range s.Get() {
-			if _, ok := vars[k]; ok {
-				return nil, fmt.Errorf("duplicated key '%v'", k)
+			if prev, ok := vars[k]; ok {
+				switch p := prev.(type) {
+				case interface{}:
+					vars[k] = []interface{}{p, v}
+				case []interface{}:
+					vars[k] = append(p, v)
+				default:
+					return nil, fmt.Errorf("multy sources merging failed")
+				}
+
+				continue
+
 			}
 			vars[k] = v
 		}
diff --git a/source/multi_test.go b/source/multi_test.go
index bf44cbb..4b49628 100644
--- a/source/multi_test.go
+++ b/source/multi_test.go
@@ -56,8 +56,14 @@ func TestMultiSourcer(t *testing.T) {
 					"key1": "var3",
 				}),
 			},
-			nil,
-			false,
+			map[string]interface{}{
+				"key1": []interface{}{
+					"var1",
+					"var3",
+				},
+				"key2": "var2",
+			},
+			true,
 		},
 	}