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// Copyright (c) Tailscale Inc & contributors
// SPDX-License-Identifier: BSD-3-Clause
// listpkgs prints the import paths that match the Go package patterns
// given on the command line and conditionally filters them in various ways.
package main
import (
"bufio"
"flag"
"fmt"
"go/build/constraint"
"log"
"os"
"slices"
"strings"
"sync"
"golang.org/x/tools/go/packages"
)
var (
ignore3p = flag.Bool("ignore-3p", false, "ignore third-party packages forked/vendored into Tailscale")
goos = flag.String("goos", "", "GOOS to use for loading packages (default: current OS)")
goarch = flag.String("goarch", "", "GOARCH to use for loading packages (default: current architecture)")
withTagsAllStr = flag.String("with-tags-all", "", "if non-empty, a comma-separated list of builds tags to require (a package will only be listed if it contains all of these build tags)")
withoutTagsAnyStr = flag.String("without-tags-any", "", "if non-empty, a comma-separated list of build constraints to exclude (a package will be omitted if it contains any of these build tags)")
shard = flag.String("shard", "", "if non-empty, a string of the form 'N/M' to only print packages in shard N of M (e.g. '1/3', '2/3', '3/3/' for different thirds of the list)")
)
func main() {
flag.Parse()
patterns := flag.Args()
if len(patterns) == 0 {
flag.Usage()
os.Exit(1)
}
cfg := &packages.Config{
Mode: packages.LoadFiles,
Env: os.Environ(),
}
if *goos != "" {
cfg.Env = append(cfg.Env, "GOOS="+*goos)
}
if *goarch != "" {
cfg.Env = append(cfg.Env, "GOARCH="+*goarch)
}
pkgs, err := packages.Load(cfg, patterns...)
if err != nil {
log.Fatalf("loading packages: %v", err)
}
var withoutAny []string
if *withoutTagsAnyStr != "" {
withoutAny = strings.Split(*withoutTagsAnyStr, ",")
}
var withAll []string
if *withTagsAllStr != "" {
withAll = strings.Split(*withTagsAllStr, ",")
}
seen := map[string]bool{}
matches := 0
Pkg:
for _, pkg := range pkgs {
if pkg.PkgPath == "" { // malformed (shouldn’t happen)
continue
}
if seen[pkg.PkgPath] {
continue // suppress duplicates when patterns overlap
}
seen[pkg.PkgPath] = true
pkgPath := pkg.PkgPath
if *ignore3p && isThirdParty(pkgPath) {
continue
}
if withAll != nil {
for _, t := range withAll {
if !hasBuildTag(pkg, t) {
continue Pkg
}
}
}
for _, t := range withoutAny {
if hasBuildTag(pkg, t) {
continue Pkg
}
}
matches++
if *shard != "" {
var n, m int
if _, err := fmt.Sscanf(*shard, "%d/%d", &n, &m); err != nil || n < 1 || m < 1 {
log.Fatalf("invalid shard format %q; expected 'N/M'", *shard)
}
if m > 0 && (matches-1)%m != n-1 {
continue // not in this shard
}
}
fmt.Println(pkgPath)
}
// If any package had errors (e.g. missing deps) report them via packages.PrintErrors.
// This mirrors `go list` behaviour when -e is *not* supplied.
if packages.PrintErrors(pkgs) > 0 {
os.Exit(1)
}
}
func isThirdParty(pkg string) bool {
return strings.HasPrefix(pkg, "tailscale.com/tempfork/")
}
// hasBuildTag reports whether any source file in pkg mentions `tag`
// in a //go:build constraint.
func hasBuildTag(pkg *packages.Package, tag string) bool {
all := slices.Concat(pkg.CompiledGoFiles, pkg.OtherFiles, pkg.IgnoredFiles)
suffix := "_" + tag + ".go"
for _, name := range all {
if strings.HasSuffix(name, suffix) {
return true
}
ok, err := fileMentionsTag(name, tag)
if err != nil {
log.Printf("reading %s: %v", name, err)
continue
}
if ok {
return true
}
}
return false
}
// tagSet is a set of build tags.
// The values are always true. We avoid non-std set types
// to make this faster to "go run" on empty caches.
type tagSet map[string]bool
var (
mu sync.Mutex
fileTags = map[string]tagSet{} // abs path -> set of build tags mentioned in file
)
func getFileTags(filename string) (tagSet, error) {
mu.Lock()
tags, ok := fileTags[filename]
mu.Unlock()
if ok {
return tags, nil
}
f, err := os.Open(filename)
if err != nil {
return nil, err
}
defer f.Close()
ts := make(tagSet)
s := bufio.NewScanner(f)
for s.Scan() {
line := s.Text()
if strings.TrimSpace(line) == "" {
continue // still in leading blank lines
}
if !strings.HasPrefix(line, "//") {
// hit real code – done with header comments
// TODO(bradfitz): care about /* */ comments?
break
}
if !strings.HasPrefix(line, "//go:build") {
continue // some other comment
}
expr, err := constraint.Parse(line)
if err != nil {
return nil, fmt.Errorf("parsing %q: %w", line, err)
}
// Call Eval to populate ts with the tags mentioned in the expression.
// We don't care about the result, just the side effect of populating ts.
expr.Eval(func(tag string) bool {
ts[tag] = true
return true // arbitrary
})
}
if err := s.Err(); err != nil {
return nil, fmt.Errorf("reading %s: %w", filename, err)
}
mu.Lock()
defer mu.Unlock()
fileTags[filename] = ts
return tags, nil
}
func fileMentionsTag(filename, tag string) (bool, error) {
tags, err := getFileTags(filename)
if err != nil {
return false, err
}
return tags[tag], nil
}
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