tstest/iosdeps: add test for forbidden iOS dependencies

Fixes #4463

Change-Id: I8305710e8a075263ae9a88a29624b19032d5beeb
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

tstest/iosdeps/iosdeps.go

@@ -0,0 +1,62 @@
+// 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 iosdeps is a just a list of the packages we import on iOS, to let us
+// test that our transitive closure of dependencies on iOS doesn't accidentally
+// grow too large, as we've historically been memory constrained there.
+package iosdeps
+
+import (
+	_ "bufio"
+	_ "bytes"
+	_ "context"
+	_ "crypto/rand"
+	_ "crypto/sha256"
+	_ "encoding/json"
+	_ "errors"
+	_ "fmt"
+	_ "io"
+	_ "io/fs"
+	_ "io/ioutil"
+	_ "log"
+	_ "math"
+	_ "net"
+	_ "net/http"
+	_ "os"
+	_ "os/signal"
+	_ "path/filepath"
+	_ "runtime"
+	_ "runtime/debug"
+	_ "strings"
+	_ "sync"
+	_ "sync/atomic"
+	_ "syscall"
+	_ "time"
+	_ "unsafe"
+
+	_ "go4.org/mem"
+	_ "golang.org/x/sys/unix"
+	_ "golang.zx2c4.com/wireguard/device"
+	_ "golang.zx2c4.com/wireguard/tun"
+	_ "inet.af/netaddr"
+	_ "tailscale.com/hostinfo"
+	_ "tailscale.com/ipn"
+	_ "tailscale.com/ipn/ipnlocal"
+	_ "tailscale.com/ipn/localapi"
+	_ "tailscale.com/log/logheap"
+	_ "tailscale.com/logtail"
+	_ "tailscale.com/logtail/filch"
+	_ "tailscale.com/net/dns"
+	_ "tailscale.com/net/tsdial"
+	_ "tailscale.com/net/tstun"
+	_ "tailscale.com/paths"
+	_ "tailscale.com/tempfork/pprof"
+	_ "tailscale.com/types/empty"
+	_ "tailscale.com/types/logger"
+	_ "tailscale.com/util/clientmetric"
+	_ "tailscale.com/util/dnsname"
+	_ "tailscale.com/version"
+	_ "tailscale.com/wgengine"
+	_ "tailscale.com/wgengine/router"
+)

tstest/iosdeps/iosdeps_test.go

@@ -0,0 +1,42 @@
+// 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.
+
+// No need to run this on Windows where CI's slow enough. Then we don't need to
+// worry about "go.exe" etc.
+
+//go:build !windows
+// +build !windows
+
+package iosdeps
+
+import (
+	"encoding/json"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"runtime"
+	"testing"
+)
+
+func TestDeps(t *testing.T) {
+	cmd := exec.Command(filepath.Join(runtime.GOROOT(), "bin", "go"), "list", "-json", ".")
+	cmd.Env = append(os.Environ(), "GOOS=ios", "GOARCH=arm64")
+	out, err := cmd.Output()
+	if err != nil {
+		t.Fatal(err)
+	}
+	var res struct {
+		Deps []string
+	}
+	if err := json.Unmarshal(out, &res); err != nil {
+		t.Fatal(err)
+	}
+	for _, dep := range res.Deps {
+		switch dep {
+		case "regexp", "regexp/syntax", "text/template", "html/template":
+			t.Errorf("package %q is not allowed as a dependency on iOS", dep)
+		}
+	}
+	t.Logf("got %d dependencies", len(res.Deps))
+}