feat(gnolang): prints nil slices as undefined

gnovm/pkg/gnolang/uverse.go

@@ -944,7 +944,20 @@ func UverseNode() *PackageNode {
 			ss := make([]string, xvl)
 			for i := 0; i < xvl; i++ {
 				ev := xv.TV.GetPointerAtIndexInt(m.Store, i).Deref()
-				ss[i] = ev.Sprint(m)
+				// TODO: Generalize this to all types.
+				if ev.T.Kind() == SliceKind || ev.T.Kind() == StringKind {
+					if ev.V == nil {
+						ss[i] = "undefined"
+					} else {
+						ss[i] = ev.Sprint(m)
+					}
+				} else {
+					if ev.T == nil {
+						ss[i] = "undefined"
+					} else {
+						ss[i] = ev.Sprint(m)
+					}
+				}
 			}
 			rs := strings.Join(ss, " ") + "\n"
 			if debug {

gnovm/pkg/gnolang/uverse_test.go

@@ -0,0 +1,83 @@
+package gnolang
+
+import (
+	"testing"
+)
+
+func TestPrintlnPrintNil(t *testing.T){
+	m := NewMachine("test", nil)
+
+	c := `package test
+	func main() {
+		var a []string
+		println(a)
+	}`
+	n := MustParseFile("main.go", c)
+	m.RunFiles(n)
+	m.RunMain()
+	assertOutput(t, c, "undefined\n")
+}
+
+func TestPrintlnFunction(t *testing.T) {
+	m := NewMachine("test", nil)
+
+	c := `package test
+	func foo(a, b int) int {
+		return a + b
+	}
+	func main() {
+		println(foo(1, 3))
+	}`
+
+	n := MustParseFile("main.go", c)
+	m.RunFiles(n)
+	m.RunMain()
+
+	assertOutput(t, c, "4\n")
+}
+
+func TestComposite(t *testing.T) {
+	m := NewMachine("test", nil)
+	c := `package test
+	func main() {
+		a, b, c, d := 1, 2, 3, 4
+		x := []int{
+			a: b,
+			c: d,
+		}
+		println(x)
+	}`
+
+	n := MustParseFile("main.go", c)
+	m.RunFiles(n)
+	m.RunMain()
+
+	assertOutput(t, c, "slice[(0 int),(2 int),(0 int),(4 int)]\n")
+}
+
+// TODO: Resolve runtime error
+// current output: g recover <nil> wtf
+func TestRecover5(t *testing.T) {
+	m := NewMachine("test", nil)
+	c := `package test
+
+	func main() {
+		f()
+	}
+
+	func f() {
+		defer func() { println("f recover", recover()) }()
+		defer g()
+		panic("wtf")
+	}
+
+	func g() {
+		println("g recover", recover())
+	}`
+
+	n := MustParseFile("main.go", c)
+	m.RunFiles(n)
+	m.RunMain()
+
+	assertOutput(t, c, "g recover wtf\nf recover wtf\n")
+}

gnovm/tests/files/print1.gno

@@ -0,0 +1,6 @@
+package main
+
+func main() {
+	var a []string
+	println(a)
+}