cmd/gomote: add missing entry in isGoToolDistGenerated

A generated file (src/time/tzdata/zzipdata.go) was added in CL 455357.

Also add a test to catch any generated files added in the future.

Updates golang/go#43350.

Change-Id: I4965744c7023a68a68609506b9cdc99a6f27ea4a
Reviewed-on: https://go-review.googlesource.com/c/build/+/463155
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Auto-Submit: Bryan Mills <bcmills@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Bryan Mills <bcmills@google.com>

Author: Bryan C. Mills

cmd/gomote/push.go

@@ -328,7 +328,8 @@ func isGoToolDistGenerated(path string) bool {
 		"src/cmd/internal/objabi/zbootstrap.go",
 		"src/go/build/zcgo.go",
 		"src/internal/buildcfg/zbootstrap.go",
-		"src/runtime/internal/sys/zversion.go":
+		"src/runtime/internal/sys/zversion.go",
+		"src/time/tzdata/zzipdata.go":
 		return true
 	}
 	return false

cmd/gomote/push_test.go

@@ -0,0 +1,91 @@
+// Copyright 2023 The Go 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 main
+
+import (
+	"bytes"
+	"io/fs"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"regexp"
+	"runtime"
+	"strings"
+	"testing"
+)
+
+func TestIsGoToolDistGenerated(t *testing.T) {
+	// This test verifies that all of the files reported by isGoToolDistGenerated
+	// are marked as generated by dist and vice-versa.
+	// This is the regexp given for such files by https://go.dev/s/generatedcode.
+	generatedRE := regexp.MustCompile(`^// Code generated by .*dist.*; DO NOT EDIT\.\n`)
+
+	goroot := runtime.GOROOT()
+	if goroot == "" {
+		cmd := exec.Command("go", "env", "GOROOT")
+		cmd.Stderr = new(strings.Builder)
+		out, err := cmd.Output()
+		goroot = string(bytes.TrimSpace(out))
+		if err != nil || goroot == "" {
+			t.Fatalf("Unable to locate GOROOT.\n%v: %v\n%s", cmd, err, cmd.Stderr)
+		}
+	}
+
+	// Add a trailing separator to follow GOROOT/src if is a symlink, as is
+	// apparently the case for some third-party distributions of the toolchain.
+	gorootSrc := filepath.Join(goroot, "src") + string(filepath.Separator)
+	t.Logf("Checking generated files in %s.", gorootSrc)
+
+	err := filepath.WalkDir(gorootSrc, func(path string, d fs.DirEntry, err error) error {
+		if err != nil {
+			return err
+		}
+
+		rel, err := filepath.Rel(goroot, path)
+		if err != nil {
+			return err
+		}
+		rel = filepath.ToSlash(rel)
+
+		got := isGoToolDistGenerated(rel)
+
+		if d.IsDir() {
+			if got {
+				t.Errorf("isGoToolDistGenerated(%q) = true, but %q is a directory", rel, rel)
+			}
+			return nil
+		}
+
+		if !got && !strings.HasPrefix(filepath.Base(path), "z") {
+			// By convention, fles generated by cmd/dist always have names starting with "z".
+			// If other files aren't matched by isGoToolDistGenerated, don't bother reading
+			// them to check.
+			return nil
+		}
+
+		b, err := os.ReadFile(path)
+		if err != nil {
+			return err
+		}
+
+		match := generatedRE.Find(b)
+		if match == nil {
+			if got {
+				t.Errorf("isGoToolDistGenerated(%q) = true; want false\n(no match for %v)", rel, generatedRE)
+			}
+		} else {
+			if !got || testing.Verbose() {
+				t.Logf("%s: %q", rel, match)
+			}
+			if !got {
+				t.Errorf("isGoToolDistGenerated(%q) = false; want true", rel)
+			}
+		}
+		return nil
+	})
+	if err != nil {
+		t.Error(err)
+	}
+}