From 766072e776bb4167187436dc69c4d212c1decd4c Mon Sep 17 00:00:00 2001
From: Mahmood Ali <mahmood@hashicorp.com>
Date: Thu, 22 Jul 2021 10:49:34 -0400
Subject: [PATCH] Protect against nil LayoutRoots

When `Renderer.LayoutRoot()` is nil, rendering should do nothing, but
currently it panics with nil pointer dereference.
---
 document.go      |  3 +++
 document_test.go | 18 ++++++++++++++++++
 2 files changed, 21 insertions(+)

diff --git a/document.go b/document.go
index 45a4407..76db4d1 100644
--- a/document.go
+++ b/document.go
@@ -185,6 +185,9 @@ func (d *Document) RenderFrame() {
 
 	// Setup our root node
 	root := d.r.LayoutRoot()
+	if root == nil {
+		return
+	}
 
 	// Build our render tree
 	tree(ctx, root, Fragment(d.els...), false)
diff --git a/document_test.go b/document_test.go
index 81300f3..22bf9b5 100644
--- a/document_test.go
+++ b/document_test.go
@@ -1,6 +1,7 @@
 package glint
 
 import (
+	"bytes"
 	"context"
 	"sync/atomic"
 	"testing"
@@ -69,6 +70,23 @@ func TestDocument_unmountClose(t *testing.T) {
 	require.Equal(uint32(1), atomic.LoadUint32(&c.unmount))
 }
 
+func TestDocument_renderingWithoutLayout(t *testing.T) {
+	var buf bytes.Buffer
+
+	d := New()
+	d.SetRenderer(&TerminalRenderer{
+		Output: &buf,
+	})
+
+	var c testMount
+	d.Append(&c)
+
+	// Render once
+	d.RenderFrame()
+	require.Empty(t, buf.String())
+	require.Zero(t, atomic.LoadUint32(&c.mount))
+}
+
 type testMount struct {
 	terminalComponent