cmd/cloner, tailcfg: fix nil vs len 0 issues, add tests, use for Hostinfo

Also use go:generate and https://golang.org/s/generatedcode header style.

Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

cmd/cloner/cloner.go

@@ -123,7 +123,7 @@ const header = `// Copyright (c) 2020 Tailscale Inc & AUTHORS All rights reserve
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// AUTO-GENERATED by: tailscale.com/cmd/cloner -type %s
+// Code generated by tailscale.com/cmd/cloner -type %s; DO NOT EDIT.
 
 package %s
 
@@ -168,8 +168,8 @@ func gen(buf *bytes.Buffer, imports map[string]struct{}, name string, typ *types
 			}
 			switch ft := ft.Underlying().(type) {
 			case *types.Slice:
-				n := importedName(ft.Elem())
 				if containsPointers(ft.Elem()) {
+					n := importedName(ft.Elem())
 					writef("dst.%s = make([]%s, len(src.%s))", fname, n, fname)
 					writef("for i := range dst.%s {", fname)
 					if _, isPtr := ft.Elem().(*types.Pointer); isPtr {
@@ -179,7 +179,7 @@ func gen(buf *bytes.Buffer, imports map[string]struct{}, name string, typ *types
 					}
 					writef("}")
 				} else {
-					writef("dst.%s = append([]%s(nil), src.%s...)", fname, n, fname)
+					writef("dst.%s = append(src.%s[:0:0], src.%s...)", fname, fname, fname)
 				}
 			case *types.Pointer:
 				if named, _ := ft.Elem().(*types.Named); named != nil && containsPointers(ft.Elem()) {

tailcfg/tailcfg.go

@@ -4,6 +4,8 @@
 
 package tailcfg
 
+//go:generate go run tailscale.com/cmd/cloner -type=User,Node,Hostinfo,NetInfo -output=tailcfg_clone.go
+
 import (
 	"bytes"
 	"errors"
@@ -371,20 +373,6 @@ func (ni *NetInfo) BasicallyEqual(ni2 *NetInfo) bool {
 		ni.LinkType == ni2.LinkType
 }
 
-// Clone makes a deep copy of Hostinfo.
-// The result aliases no memory with the original.
-//
-// TODO: use cmd/cloner, reconcile len(0) vs. nil.
-func (h *Hostinfo) Clone() (res *Hostinfo) {
-	res = new(Hostinfo)
-	*res = *h
-
-	res.RoutableIPs = append([]wgcfg.CIDR{}, h.RoutableIPs...)
-	res.Services = append([]Service{}, h.Services...)
-	res.NetInfo = h.NetInfo.Clone()
-	return res
-}
-
 // Equal reports whether h and h2 are equal.
 func (h *Hostinfo) Equal(h2 *Hostinfo) bool {
 	if h == nil && h2 == nil {

tailcfg/tailcfg_clone.go

@@ -2,12 +2,11 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// AUTO-GENERATED by tailscale.com/cmd/cloner -type User,Node,NetInfo
+// Code generated by tailscale.com/cmd/cloner -type User,Node,Hostinfo,NetInfo; DO NOT EDIT.
 
 package tailcfg
 
 import (
-	"github.com/tailscale/wireguard-go/wgcfg"
 	"time"
 )
 
@@ -19,8 +18,8 @@ func (src *User) Clone() *User {
 	}
 	dst := new(User)
 	*dst = *src
-	dst.Logins = append([]LoginID(nil), src.Logins...)
-	dst.Roles = append([]RoleID(nil), src.Roles...)
+	dst.Logins = append(src.Logins[:0:0], src.Logins...)
+	dst.Roles = append(src.Roles[:0:0], src.Roles...)
 	return dst
 }
 
@@ -32,9 +31,9 @@ func (src *Node) Clone() *Node {
 	}
 	dst := new(Node)
 	*dst = *src
-	dst.Addresses = append([]wgcfg.CIDR(nil), src.Addresses...)
-	dst.AllowedIPs = append([]wgcfg.CIDR(nil), src.AllowedIPs...)
-	dst.Endpoints = append([]string(nil), src.Endpoints...)
+	dst.Addresses = append(src.Addresses[:0:0], src.Addresses...)
+	dst.AllowedIPs = append(src.AllowedIPs[:0:0], src.AllowedIPs...)
+	dst.Endpoints = append(src.Endpoints[:0:0], src.Endpoints...)
 	dst.Hostinfo = *src.Hostinfo.Clone()
 	if dst.LastSeen != nil {
 		dst.LastSeen = new(time.Time)
@@ -43,6 +42,21 @@ func (src *Node) Clone() *Node {
 	return dst
 }
 
+// Clone makes a deep copy of Hostinfo.
+// The result aliases no memory with the original.
+func (src *Hostinfo) Clone() *Hostinfo {
+	if src == nil {
+		return nil
+	}
+	dst := new(Hostinfo)
+	*dst = *src
+	dst.RoutableIPs = append(src.RoutableIPs[:0:0], src.RoutableIPs...)
+	dst.RequestTags = append(src.RequestTags[:0:0], src.RequestTags...)
+	dst.Services = append(src.Services[:0:0], src.Services...)
+	dst.NetInfo = src.NetInfo.Clone()
+	return dst
+}
+
 // Clone makes a deep copy of NetInfo.
 // The result aliases no memory with the original.
 func (src *NetInfo) Clone() *NetInfo {

tailcfg/tailcfg_test.go

@@ -390,3 +390,43 @@ func testKey(t *testing.T, prefix string, in keyIn, out encoding.TextUnmarshaler
 		t.Errorf("mismatch after unmarshal")
 	}
 }
+
+func TestCloneUser(t *testing.T) {
+	tests := []struct {
+		name string
+		u    *User
+	}{
+		{"nil_logins", &User{}},
+		{"zero_logins", &User{Logins: make([]LoginID, 0)}},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			u2 := tt.u.Clone()
+			if !reflect.DeepEqual(tt.u, u2) {
+				t.Errorf("not equal")
+			}
+		})
+	}
+}
+
+func TestCloneNode(t *testing.T) {
+	tests := []struct {
+		name string
+		v    *Node
+	}{
+		{"nil_fields", &Node{}},
+		{"zero_fields", &Node{
+			Addresses:  make([]wgcfg.CIDR, 0),
+			AllowedIPs: make([]wgcfg.CIDR, 0),
+			Endpoints:  make([]string, 0),
+		}},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			v2 := tt.v.Clone()
+			if !reflect.DeepEqual(tt.v, v2) {
+				t.Errorf("not equal")
+			}
+		})
+	}
+}