From cf3a12bf0d4ddad6ed067e85f0c9a1ef1a05447a Mon Sep 17 00:00:00 2001
From: Leon Mika <lmika@lmika.org>
Date: Sat, 4 May 2024 10:14:44 +1000
Subject: [PATCH] Fixed a few bugs with the 'index' builtin

---
 ucl/builtins.go          |  2 +-
 ucl/inst.go              |  1 -
 ucl/objs.go              | 14 +++++++++++++-
 ucl/testbuiltins_test.go | 33 ++++++++++++++++++++++++++++++---
 4 files changed, 44 insertions(+), 6 deletions(-)

diff --git a/ucl/builtins.go b/ucl/builtins.go
index a13544d..a9ad5f0 100644
--- a/ucl/builtins.go
+++ b/ucl/builtins.go
@@ -144,7 +144,7 @@ func indexBuiltin(ctx context.Context, args invocationArgs) (object, error) {
 		case listable:
 			intIdx, ok := idx.(intObject)
 			if !ok {
-				return nil, errors.New("expected int for listable")
+				return nil, nil
 			}
 			if int(intIdx) >= 0 && int(intIdx) < v.Len() {
 				val = v.Index(int(intIdx))
diff --git a/ucl/inst.go b/ucl/inst.go
index 0eef348..8fa9561 100644
--- a/ucl/inst.go
+++ b/ucl/inst.go
@@ -36,7 +36,6 @@ func New(opts ...InstOption) *Inst {
 	rootEC.addCmd("echo", invokableFunc(echoBuiltin))
 	rootEC.addCmd("set", invokableFunc(setBuiltin))
 	rootEC.addCmd("toUpper", invokableFunc(toUpperBuiltin))
-	//rootEC.addCmd("cat", invokableFunc(catBuiltin))
 	rootEC.addCmd("len", invokableFunc(lenBuiltin))
 	rootEC.addCmd("index", invokableFunc(indexBuiltin))
 	rootEC.addCmd("call", invokableFunc(callBuiltin))
diff --git a/ucl/objs.go b/ucl/objs.go
index bfa3081..3d3373d 100644
--- a/ucl/objs.go
+++ b/ucl/objs.go
@@ -425,7 +425,19 @@ func (s structProxyObject) Len() int {
 }
 
 func (s structProxyObject) Value(k string) object {
-	e, err := fromGoValue(s.v.FieldByName(k).Interface())
+	f := s.v.FieldByName(k)
+	if !f.IsValid() {
+		return nil
+	}
+
+	if f.Kind() == reflect.Ptr {
+		if f.IsNil() {
+			return nil
+		}
+		f = f.Elem()
+	}
+
+	e, err := fromGoValue(f.Interface())
 	if err != nil {
 		return nil
 	}
diff --git a/ucl/testbuiltins_test.go b/ucl/testbuiltins_test.go
index 11f6c8d..10a16ab 100644
--- a/ucl/testbuiltins_test.go
+++ b/ucl/testbuiltins_test.go
@@ -524,9 +524,21 @@ func TestBuiltins_Index(t *testing.T) {
 
 		{desc: "go list 1", expr: `goInt | index 1`, want: "5\n"},
 		{desc: "go list 2", expr: `goInt | index 2`, want: "4\n"},
+		{desc: "go list 3", expr: `goInt | index 555`, want: "(nil)\n"},
+		{desc: "go list 4", expr: `goInt | index -12`, want: "(nil)\n"},
+		{desc: "go list 5", expr: `goInt | index NotAnIndex`, want: "(nil)\n"},
 		{desc: "go struct 1", expr: `goStruct | index Alpha`, want: "foo\n"},
 		{desc: "go struct 2", expr: `goStruct | index Beta`, want: "bar\n"},
 		{desc: "go struct 3", expr: `goStruct | index Gamma 1`, want: "33\n"},
+		{desc: "go struct 4", expr: `goStruct | index Nested This`, want: "fla\n"},
+		{desc: "go struct 5", expr: `goStruct | index Nested That`, want: "132\n"},
+		{desc: "go struct 6", expr: `goStruct | index NestedPtr This`, want: "flaPtr\n"},
+		{desc: "go struct 7", expr: `goStruct | index NestedPtr That`, want: "6678\n"},
+		{desc: "go struct 8", expr: `goStruct | index Missing`, want: "(nil)\n"},
+		{desc: "go struct 9", expr: `goStruct | index Nested Missing 123 Stuff`, want: "(nil)\n"},
+		{desc: "go struct 10", expr: `goStruct | index NestedPtrNil`, want: "(nil)\n"},
+		{desc: "go struct 11", expr: `goStruct | index NestedPtrNil This`, want: "(nil)\n"},
+		{desc: "go struct 12", expr: `goStruct | index NestedPtrNil Missing`, want: "(nil)\n"},
 	}
 
 	for _, tt := range tests {
@@ -539,14 +551,29 @@ func TestBuiltins_Index(t *testing.T) {
 				return []int{6, 5, 4}, nil
 			})
 			inst.SetBuiltin("goStruct", func(ctx context.Context, args CallArgs) (any, error) {
+				type nested struct {
+					This string
+					That int
+				}
 				return struct {
-					Alpha string
-					Beta  string
-					Gamma []int
+					Alpha        string
+					Beta         string
+					Gamma        []int
+					Nested       nested
+					NestedPtr    *nested
+					NestedPtrNil *nested
 				}{
 					Alpha: "foo",
 					Beta:  "bar",
 					Gamma: []int{22, 33},
+					Nested: nested{
+						This: "fla",
+						That: 132,
+					},
+					NestedPtr: &nested{
+						This: "flaPtr",
+						That: 6678,
+					},
 				}, nil
 			})
 			err := EvalAndDisplay(ctx, inst, tt.expr)