cmd/viewer: add codegen tool for Views

Signed-off-by: Maisem Ali <maisem@tailscale.com>

cmd/viewer/tests/tests.go

@@ -0,0 +1,48 @@
+// Copyright (c) 2022 Tailscale Inc & AUTHORS All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package tests serves a list of tests for tailscale.com/cmd/viewer.
+package tests
+
+import (
+	"fmt"
+
+	"inet.af/netaddr"
+)
+
+//go:generate go run tailscale.com/cmd/viewer --type=StructWithPtrs,StructWithoutPtrs,Map,StructWithSlices
+
+type StructWithoutPtrs struct {
+	Int int
+	Pfx netaddr.IPPrefix
+}
+
+type Map struct {
+	M map[string]int
+}
+
+type StructWithPtrs struct {
+	Value *StructWithoutPtrs
+	Int   *int
+
+	NoCloneValue *StructWithoutPtrs `codegen:"noclone"`
+}
+
+func (v *StructWithPtrs) String() string { return fmt.Sprintf("%v", v.Int) }
+
+func (v *StructWithPtrs) Equal(v2 *StructWithPtrs) bool {
+	return v.Value == v2.Value
+}
+
+type StructWithSlices struct {
+	Values         []StructWithoutPtrs
+	ValuePointers  []*StructWithoutPtrs
+	StructPointers []*StructWithPtrs
+	Structs        []StructWithPtrs
+	Ints           []*int
+
+	Slice    []string
+	Prefixes []netaddr.IPPrefix
+	Data     []byte
+}