From e3e49cc099efaabe9713f5602e42bb87d1c46670 Mon Sep 17 00:00:00 2001
From: Mateusz Gozdek <mateusz@kinvolk.io>
Date: Wed, 15 Jan 2020 13:30:47 +0100
Subject: [PATCH] gohcl/decode.go: fix decoding value slices

Currently, if user tries to decode such scenario, it results in
"slice index out of range".

Fixes regression introduced in 42351b1d15716a53accce7144d13df5606d56b19.

Signed-off-by: Mateusz Gozdek <mateusz@kinvolk.io>
---
 gohcl/decode.go      |  3 +++
 gohcl/decode_test.go | 31 +++++++++++++++++++++++++++++++
 2 files changed, 34 insertions(+)

diff --git a/gohcl/decode.go b/gohcl/decode.go
index f0d589d7..6079a01e 100644
--- a/gohcl/decode.go
+++ b/gohcl/decode.go
@@ -185,6 +185,9 @@ func decodeBodyToStruct(body hcl.Body, ctx *hcl.EvalContext, val reflect.Value)
 					diags = append(diags, decodeBlockToValue(block, ctx, v.Elem())...)
 					sli.Index(i).Set(v)
 				} else {
+					if i >= sli.Len() {
+						sli = reflect.Append(sli, reflect.Indirect(reflect.New(ty)))
+					}
 					diags = append(diags, decodeBlockToValue(block, ctx, sli.Index(i))...)
 				}
 			}
diff --git a/gohcl/decode_test.go b/gohcl/decode_test.go
index 8f065c46..5260a0e4 100644
--- a/gohcl/decode_test.go
+++ b/gohcl/decode_test.go
@@ -37,6 +37,10 @@ func TestDecodeBody(t *testing.T) {
 		Nested []*withTwoAttributes `hcl:"nested,block"`
 	}
 
+	type withListofNestedBlocksNoPointers struct {
+		Nested []withTwoAttributes `hcl:"nested,block"`
+	}
+
 	tests := []struct {
 		Body      map[string]interface{}
 		Target    func() interface{}
@@ -623,6 +627,33 @@ func TestDecodeBody(t *testing.T) {
 			},
 			0,
 		},
+		{
+			// Make sure decoding value slices works the same as pointer slices.
+			map[string]interface{}{
+				"nested": []map[string]interface{}{
+					{
+						"b": "bar",
+					},
+					{
+						"b": "baz",
+					},
+				},
+			},
+			func() interface{} {
+				return &withListofNestedBlocksNoPointers{
+					Nested: []withTwoAttributes{
+						{
+							B: "foo",
+						},
+					},
+				}
+			},
+			func(gotI interface{}) bool {
+				n := gotI.(withListofNestedBlocksNoPointers)
+				return n.Nested[0].B == "bar" && len(n.Nested) == 2
+			},
+			0,
+		},
 	}
 
 	for i, test := range tests {