src/go/build/deps_test.go

   1 // Copyright 2022 The Go Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style
   3 // license that can be found in the LICENSE file.
   4
   5 // This file exercises the import parser but also checks that
   6 // some low-level packages do not have new dependencies added.
   7
   8 package build
   9
  10 import (
  11         "bytes"
  12         "fmt"
  13         "go/token"
  14         "internal/dag"
  15         "internal/testenv"
  16         "io/fs"
  17         "os"
  18         "path/filepath"
  19         "runtime"
  20         "sort"
  21         "strings"
  22         "testing"
  23 )
  24
  25 // depsRules defines the expected dependencies between packages in
  26 // the Go source tree. It is a statement of policy.
  27 //
  28 // DO NOT CHANGE THIS DATA TO FIX BUILDS.
  29 // Existing packages should not have their constraints relaxed
  30 // without prior discussion.
  31 // Negative assertions should almost never be removed.
  32 //
  33 // "a < b" means package b can import package a.
  34 //
  35 // See `go doc internal/dag' for the full syntax.
  36 //
  37 // All-caps names are pseudo-names for specific points
  38 // in the dependency lattice.
  39 var depsRules = `
  40         # No dependencies allowed for any of these packages.
  41         NONE
  42         < constraints, container/list, container/ring,
  43           internal/cfg, internal/coverage, internal/coverage/rtcov,
  44           internal/coverage/uleb128, internal/coverage/calloc,
  45           internal/cpu, internal/goarch,
  46           internal/goexperiment, internal/goos,
  47           internal/goversion, internal/nettrace, internal/platform,
  48           log/internal,
  49           maps, slices, unicode/utf8, unicode/utf16, unicode,
  50           unsafe;
  51
  52         # These packages depend only on internal/goarch and unsafe.
  53         internal/goarch, unsafe
  54         < internal/abi;
  55
  56         # RUNTIME is the core runtime group of packages, all of them very light-weight.
  57         internal/abi, internal/cpu, internal/goarch,
  58         internal/coverage/rtcov, internal/goexperiment,
  59         internal/goos, unsafe
  60         < internal/bytealg
  61         < internal/itoa
  62         < internal/unsafeheader
  63         < runtime/internal/sys
  64         < runtime/internal/syscall
  65         < runtime/internal/atomic
  66         < runtime/internal/math
  67         < runtime
  68         < sync/atomic
  69         < internal/race
  70         < sync
  71         < internal/godebug
  72         < internal/reflectlite
  73         < errors
  74         < internal/oserror, math/bits
  75         < RUNTIME;
  76
  77         RUNTIME
  78         < sort
  79         < container/heap;
  80
  81         RUNTIME
  82         < io;
  83
  84         RUNTIME
  85         < arena;
  86
  87         syscall !< io;
  88         reflect !< sort;
  89
  90         RUNTIME, unicode/utf8
  91         < path;
  92
  93         unicode !< path;
  94
  95         # SYSCALL is RUNTIME plus the packages necessary for basic system calls.
  96         RUNTIME, unicode/utf8, unicode/utf16
  97         < internal/syscall/windows/sysdll, syscall/js
  98         < syscall
  99         < internal/syscall/unix, internal/syscall/windows, internal/syscall/windows/registry
 100         < internal/syscall/execenv
 101         < SYSCALL;
 102
 103         # TIME is SYSCALL plus the core packages about time, including context.
 104         SYSCALL
 105         < time/tzdata
 106         < time
 107         < context
 108         < TIME;
 109
 110         TIME, io, path, sort
 111         < io/fs;
 112
 113         # MATH is RUNTIME plus the basic math packages.
 114         RUNTIME
 115         < math
 116         < MATH;
 117
 118         unicode !< math;
 119
 120         MATH
 121         < math/cmplx;
 122
 123         MATH
 124         < math/rand;
 125
 126         MATH
 127         < runtime/metrics;
 128
 129         MATH, unicode/utf8
 130         < strconv;
 131
 132         unicode !< strconv;
 133
 134         # STR is basic string and buffer manipulation.
 135         RUNTIME, io, unicode/utf8, unicode/utf16, unicode
 136         < bytes, strings
 137         < bufio;
 138
 139         bufio, path, strconv
 140         < STR;
 141
 142         # OS is basic OS access, including helpers (path/filepath, os/exec, etc).
 143         # OS includes string routines, but those must be layered above package os.
 144         # OS does not include reflection.
 145         io/fs
 146         < internal/testlog
 147         < internal/poll
 148         < internal/safefilepath
 149         < os
 150         < os/signal;
 151
 152         io/fs
 153         < embed;
 154
 155         unicode, fmt !< net, os, os/signal;
 156
 157         os/signal, STR
 158         < path/filepath
 159         < io/ioutil;
 160
 161         path/filepath, internal/godebug < os/exec;
 162
 163         io/ioutil, os/exec, os/signal
 164         < OS;
 165
 166         reflect !< OS;
 167
 168         OS
 169         < golang.org/x/sys/cpu;
 170
 171         # FMT is OS (which includes string routines) plus reflect and fmt.
 172         # It does not include package log, which should be avoided in core packages.
 173         arena, strconv, unicode
 174         < reflect;
 175
 176         os, reflect
 177         < internal/fmtsort
 178         < fmt;
 179
 180         OS, fmt
 181         < FMT;
 182
 183         log !< FMT;
 184
 185         # Misc packages needing only FMT.
 186         FMT
 187         < html,
 188           internal/dag,
 189           internal/goroot,
 190           internal/types/errors,
 191           mime/quotedprintable,
 192           net/internal/socktest,
 193           net/url,
 194           runtime/trace,
 195           text/scanner,
 196           text/tabwriter;
 197
 198         io, reflect
 199         < internal/saferio;
 200
 201         # encodings
 202         # core ones do not use fmt.
 203         io, strconv
 204         < encoding;
 205
 206         encoding, reflect
 207         < encoding/binary
 208         < encoding/base32, encoding/base64;
 209
 210         FMT, encoding < flag;
 211
 212         fmt !< encoding/base32, encoding/base64;
 213
 214         FMT, encoding/base32, encoding/base64, internal/saferio
 215         < encoding/ascii85, encoding/csv, encoding/gob, encoding/hex,
 216           encoding/json, encoding/pem, encoding/xml, mime;
 217
 218         # hashes
 219         io
 220         < hash
 221         < hash/adler32, hash/crc32, hash/crc64, hash/fnv;
 222
 223         # math/big
 224         FMT, encoding/binary, math/rand
 225         < math/big;
 226
 227         # compression
 228         FMT, encoding/binary, hash/adler32, hash/crc32
 229         < compress/bzip2, compress/flate, compress/lzw
 230         < archive/zip, compress/gzip, compress/zlib;
 231
 232         # templates
 233         FMT
 234         < text/template/parse;
 235
 236         net/url, text/template/parse
 237         < text/template
 238         < internal/lazytemplate;
 239
 240         encoding/json, html, text/template
 241         < html/template;
 242
 243         # regexp
 244         FMT
 245         < regexp/syntax
 246         < regexp
 247         < internal/lazyregexp;
 248
 249         # suffix array
 250         encoding/binary, regexp
 251         < index/suffixarray;
 252
 253         # executable parsing
 254         FMT, encoding/binary, compress/zlib, internal/saferio
 255         < runtime/debug
 256         < debug/dwarf
 257         < debug/elf, debug/gosym, debug/macho, debug/pe, debug/plan9obj, internal/xcoff
 258         < debug/buildinfo
 259         < DEBUG;
 260
 261         # go parser and friends.
 262         FMT
 263         < go/token
 264         < go/scanner
 265         < go/ast
 266         < go/internal/typeparams
 267         < go/parser;
 268
 269         FMT
 270         < go/build/constraint, go/doc/comment;
 271
 272         go/build/constraint, go/doc/comment, go/parser, text/tabwriter
 273         < go/printer
 274         < go/format;
 275
 276         go/doc/comment, go/parser, internal/lazyregexp, text/template
 277         < go/doc;
 278
 279         math/big, go/token
 280         < go/constant;
 281
 282         container/heap, go/constant, go/parser, internal/types/errors, internal/lazyregexp
 283         < go/types;
 284
 285         FMT, internal/goexperiment
 286         < internal/buildcfg;
 287
 288         go/build/constraint, go/doc, go/parser, internal/buildcfg, internal/goroot, internal/goversion
 289         < go/build;
 290
 291         # databases
 292         FMT
 293         < database/sql/internal
 294         < database/sql/driver
 295         < database/sql;
 296
 297         # images
 298         FMT, compress/lzw, compress/zlib
 299         < image/color
 300         < image, image/color/palette
 301         < image/internal/imageutil
 302         < image/draw
 303         < image/gif, image/jpeg, image/png;
 304
 305         # cgo, delayed as long as possible.
 306         # If you add a dependency on CGO, you must add the package
 307         # to cgoPackages in cmd/dist/test.go as well.
 308         RUNTIME
 309         < C
 310         < runtime/cgo
 311         < CGO
 312         < runtime/msan, runtime/asan;
 313
 314         # runtime/race
 315         NONE < runtime/race/internal/amd64v1;
 316         NONE < runtime/race/internal/amd64v3;
 317         CGO, runtime/race/internal/amd64v1, runtime/race/internal/amd64v3 < runtime/race;
 318
 319         # Bulk of the standard library must not use cgo.
 320         # The prohibition stops at net and os/user.
 321         C !< fmt, go/types, CRYPTO-MATH, log/slog;
 322
 323         CGO, OS
 324         < plugin;
 325
 326         CGO, FMT
 327         < os/user
 328         < archive/tar;
 329
 330         sync
 331         < internal/singleflight;
 332
 333         os
 334         < golang.org/x/net/dns/dnsmessage,
 335           golang.org/x/net/lif,
 336           golang.org/x/net/route;
 337
 338         os, runtime, strconv, sync, unsafe,
 339         internal/godebug
 340         < internal/intern;
 341
 342         internal/bytealg, internal/intern, internal/itoa, math/bits, sort, strconv
 343         < net/netip;
 344
 345         # net is unavoidable when doing any networking,
 346         # so large dependencies must be kept out.
 347         # This is a long-looking list but most of these
 348         # are small with few dependencies.
 349         CGO,
 350         golang.org/x/net/dns/dnsmessage,
 351         golang.org/x/net/lif,
 352         golang.org/x/net/route,
 353         internal/godebug,
 354         internal/nettrace,
 355         internal/poll,
 356         internal/singleflight,
 357         internal/race,
 358         net/netip,
 359         os
 360         < net;
 361
 362         fmt, unicode !< net;
 363         math/rand !< net; # net uses runtime instead
 364
 365         # NET is net plus net-helper packages.
 366         FMT, net
 367         < net/textproto;
 368
 369         mime, net/textproto, net/url
 370         < NET;
 371
 372         # logging - most packages should not import; http and up is allowed
 373         FMT, log/internal
 374         < log;
 375
 376         log, log/slog !< crypto/tls, database/sql, go/importer, testing;
 377
 378         FMT, log, net
 379         < log/syslog;
 380
 381         RUNTIME
 382         < log/slog/internal, log/slog/internal/buffer;
 383
 384         FMT,
 385         encoding, encoding/json,
 386         log, log/internal,
 387         log/slog/internal, log/slog/internal/buffer,
 388         slices
 389         < log/slog
 390         < log/slog/internal/slogtest, log/slog/internal/benchmarks;
 391
 392         NET, log
 393         < net/mail;
 394
 395         NONE < crypto/internal/boring/sig, crypto/internal/boring/syso;
 396         sync/atomic < crypto/internal/boring/bcache, crypto/internal/boring/fipstls;
 397         crypto/internal/boring/sig, crypto/internal/boring/fipstls < crypto/tls/fipsonly;
 398
 399         # CRYPTO is core crypto algorithms - no cgo, fmt, net.
 400         # Unfortunately, stuck with reflect via encoding/binary.
 401         crypto/internal/boring/sig,
 402         crypto/internal/boring/syso,
 403         encoding/binary,
 404         golang.org/x/sys/cpu,
 405         hash, embed
 406         < crypto
 407         < crypto/subtle
 408         < crypto/internal/alias
 409         < crypto/cipher;
 410
 411         crypto/cipher,
 412         crypto/internal/boring/bcache
 413         < crypto/internal/boring
 414         < crypto/boring;
 415
 416         crypto/internal/alias
 417         < crypto/internal/randutil
 418         < crypto/internal/nistec/fiat
 419         < crypto/internal/nistec
 420         < crypto/internal/edwards25519/field
 421         < crypto/internal/edwards25519;
 422
 423         crypto/boring
 424         < crypto/aes, crypto/des, crypto/hmac, crypto/md5, crypto/rc4,
 425           crypto/sha1, crypto/sha256, crypto/sha512;
 426
 427         crypto/boring, crypto/internal/edwards25519/field
 428         < crypto/ecdh;
 429
 430         crypto/aes,
 431         crypto/des,
 432         crypto/ecdh,
 433         crypto/hmac,
 434         crypto/internal/edwards25519,
 435         crypto/md5,
 436         crypto/rc4,
 437         crypto/sha1,
 438         crypto/sha256,
 439         crypto/sha512
 440         < CRYPTO;
 441
 442         CGO, fmt, net !< CRYPTO;
 443
 444         # CRYPTO-MATH is core bignum-based crypto - no cgo, net; fmt now ok.
 445         CRYPTO, FMT, math/big
 446         < crypto/internal/boring/bbig
 447         < crypto/rand
 448         < crypto/ed25519
 449         < encoding/asn1
 450         < golang.org/x/crypto/cryptobyte/asn1
 451         < golang.org/x/crypto/cryptobyte
 452         < crypto/internal/bigmod
 453         < crypto/dsa, crypto/elliptic, crypto/rsa
 454         < crypto/ecdsa
 455         < CRYPTO-MATH;
 456
 457         CGO, net !< CRYPTO-MATH;
 458
 459         # TLS, Prince of Dependencies.
 460         CRYPTO-MATH, NET, container/list, encoding/hex, encoding/pem
 461         < golang.org/x/crypto/internal/alias
 462         < golang.org/x/crypto/internal/subtle
 463         < golang.org/x/crypto/chacha20
 464         < golang.org/x/crypto/internal/poly1305
 465         < golang.org/x/crypto/chacha20poly1305
 466         < golang.org/x/crypto/hkdf
 467         < crypto/x509/internal/macos
 468         < crypto/x509/pkix;
 469
 470         crypto/internal/boring/fipstls, crypto/x509/pkix
 471         < crypto/x509
 472         < crypto/tls;
 473
 474         # crypto-aware packages
 475
 476         DEBUG, go/build, go/types, text/scanner, crypto/md5
 477         < internal/pkgbits
 478         < go/internal/gcimporter, go/internal/gccgoimporter, go/internal/srcimporter
 479         < go/importer;
 480
 481         NET, crypto/rand, mime/quotedprintable
 482         < mime/multipart;
 483
 484         crypto/tls
 485         < net/smtp;
 486
 487         crypto/rand
 488         < hash/maphash; # for purego implementation
 489
 490         # HTTP, King of Dependencies.
 491
 492         FMT
 493         < golang.org/x/net/http2/hpack
 494         < net/http/internal, net/http/internal/ascii, net/http/internal/testcert;
 495
 496         FMT, NET, container/list, encoding/binary, log
 497         < golang.org/x/text/transform
 498         < golang.org/x/text/unicode/norm
 499         < golang.org/x/text/unicode/bidi
 500         < golang.org/x/text/secure/bidirule
 501         < golang.org/x/net/idna
 502         < golang.org/x/net/http/httpguts, golang.org/x/net/http/httpproxy;
 503
 504         NET, crypto/tls
 505         < net/http/httptrace;
 506
 507         compress/gzip,
 508         golang.org/x/net/http/httpguts,
 509         golang.org/x/net/http/httpproxy,
 510         golang.org/x/net/http2/hpack,
 511         net/http/internal,
 512         net/http/internal/ascii,
 513         net/http/internal/testcert,
 514         net/http/httptrace,
 515         mime/multipart,
 516         log
 517         < net/http;
 518
 519         # HTTP-aware packages
 520
 521         encoding/json, net/http
 522         < expvar;
 523
 524         net/http, net/http/internal/ascii
 525         < net/http/cookiejar, net/http/httputil;
 526
 527         net/http, flag
 528         < net/http/httptest;
 529
 530         net/http, regexp
 531         < net/http/cgi
 532         < net/http/fcgi;
 533
 534         # Profiling
 535         FMT, compress/gzip, encoding/binary, text/tabwriter
 536         < runtime/pprof;
 537
 538         OS, compress/gzip, internal/lazyregexp
 539         < internal/profile;
 540
 541         html, internal/profile, net/http, runtime/pprof, runtime/trace
 542         < net/http/pprof;
 543
 544         # RPC
 545         encoding/gob, encoding/json, go/token, html/template, net/http
 546         < net/rpc
 547         < net/rpc/jsonrpc;
 548
 549         # System Information
 550         internal/cpu, sync
 551         < internal/sysinfo;
 552
 553         # Test-only
 554         log
 555         < testing/iotest
 556         < testing/fstest;
 557
 558         FMT, flag, math/rand
 559         < testing/quick;
 560
 561         FMT, DEBUG, flag, runtime/trace, internal/sysinfo, math/rand
 562         < testing;
 563
 564         FMT, crypto/sha256, encoding/json, go/ast, go/parser, go/token,
 565         internal/godebug, math/rand, encoding/hex, crypto/sha256
 566         < internal/fuzz;
 567
 568         internal/fuzz, internal/testlog, runtime/pprof, regexp
 569         < testing/internal/testdeps;
 570
 571         OS, flag, testing, internal/cfg, internal/platform, internal/goroot
 572         < internal/testenv;
 573
 574         OS, encoding/base64
 575         < internal/obscuretestdata;
 576
 577         CGO, OS, fmt
 578         < internal/testpty;
 579
 580         NET, testing, math/rand
 581         < golang.org/x/net/nettest;
 582
 583         syscall
 584         < os/exec/internal/fdtest;
 585
 586         FMT, container/heap, math/rand
 587         < internal/trace;
 588
 589         FMT
 590         < internal/diff, internal/txtar;
 591
 592         FMT, crypto/md5, encoding/binary, regexp, sort, text/tabwriter, unsafe,
 593         internal/coverage, internal/coverage/uleb128
 594         < internal/coverage/cmerge,
 595           internal/coverage/pods,
 596           internal/coverage/slicereader,
 597           internal/coverage/slicewriter;
 598
 599         internal/coverage/slicereader, internal/coverage/slicewriter
 600         < internal/coverage/stringtab
 601         < internal/coverage/decodecounter, internal/coverage/decodemeta,
 602           internal/coverage/encodecounter, internal/coverage/encodemeta;
 603
 604         internal/coverage/cmerge
 605         < internal/coverage/cformat;
 606
 607         runtime/debug,
 608         internal/coverage/calloc,
 609         internal/coverage/cformat,
 610         internal/coverage/decodecounter, internal/coverage/decodemeta,
 611         internal/coverage/encodecounter, internal/coverage/encodemeta,
 612         internal/coverage/pods
 613         < runtime/coverage;
 614 `
 615
 616 // listStdPkgs returns the same list of packages as "go list std".
 617 func listStdPkgs(goroot string) ([]string, error) {
 618         // Based on cmd/go's matchPackages function.
 619         var pkgs []string
 620
 621         src := filepath.Join(goroot, "src") + string(filepath.Separator)
 622         walkFn := func(path string, d fs.DirEntry, err error) error {
 623                 if err != nil || !d.IsDir() || path == src {
 624                         return nil
 625                 }
 626
 627                 base := filepath.Base(path)
 628                 if strings.HasPrefix(base, ".") || strings.HasPrefix(base, "_") || base == "testdata" {
 629                         return filepath.SkipDir
 630                 }
 631
 632                 name := filepath.ToSlash(path[len(src):])
 633                 if name == "builtin" || name == "cmd" {
 634                         return filepath.SkipDir
 635                 }
 636
 637                 pkgs = append(pkgs, strings.TrimPrefix(name, "vendor/"))
 638                 return nil
 639         }
 640         if err := filepath.WalkDir(src, walkFn); err != nil {
 641                 return nil, err
 642         }
 643         return pkgs, nil
 644 }
 645
 646 func TestDependencies(t *testing.T) {
 647         if !testenv.HasSrc() {
 648                 // Tests run in a limited file system and we do not
 649                 // provide access to every source file.
 650                 t.Skipf("skipping on %s/%s, missing full GOROOT", runtime.GOOS, runtime.GOARCH)
 651         }
 652
 653         ctxt := Default
 654         all, err := listStdPkgs(ctxt.GOROOT)
 655         if err != nil {
 656                 t.Fatal(err)
 657         }
 658         sort.Strings(all)
 659
 660         sawImport := map[string]map[string]bool{} // from package => to package => true
 661         policy := depsPolicy(t)
 662
 663         for _, pkg := range all {
 664                 imports, err := findImports(pkg)
 665                 if err != nil {
 666                         t.Error(err)
 667                         continue
 668                 }
 669                 if sawImport[pkg] == nil {
 670                         sawImport[pkg] = map[string]bool{}
 671                 }
 672                 var bad []string
 673                 for _, imp := range imports {
 674                         sawImport[pkg][imp] = true
 675                         if !policy.HasEdge(pkg, imp) {
 676                                 bad = append(bad, imp)
 677                         }
 678                 }
 679                 if bad != nil {
 680                         t.Errorf("unexpected dependency: %s imports %v", pkg, bad)
 681                 }
 682         }
 683 }
 684
 685 var buildIgnore = []byte("\n//go:build ignore")
 686
 687 func findImports(pkg string) ([]string, error) {
 688         vpkg := pkg
 689         if strings.HasPrefix(pkg, "golang.org") {
 690                 vpkg = "vendor/" + pkg
 691         }
 692         dir := filepath.Join(Default.GOROOT, "src", vpkg)
 693         files, err := os.ReadDir(dir)
 694         if err != nil {
 695                 return nil, err
 696         }
 697         var imports []string
 698         var haveImport = map[string]bool{}
 699         if pkg == "crypto/internal/boring" {
 700                 haveImport["C"] = true // kludge: prevent C from appearing in crypto/internal/boring imports
 701         }
 702         fset := token.NewFileSet()
 703         for _, file := range files {
 704                 name := file.Name()
 705                 if name == "slice_go14.go" || name == "slice_go18.go" {
 706                         // These files are for compiler bootstrap with older versions of Go and not built in the standard build.
 707                         continue
 708                 }
 709                 if !strings.HasSuffix(name, ".go") || strings.HasSuffix(name, "_test.go") {
 710                         continue
 711                 }
 712                 info := fileInfo{
 713                         name: filepath.Join(dir, name),
 714                         fset: fset,
 715                 }
 716                 f, err := os.Open(info.name)
 717                 if err != nil {
 718                         return nil, err
 719                 }
 720                 err = readGoInfo(f, &info)
 721                 f.Close()
 722                 if err != nil {
 723                         return nil, fmt.Errorf("reading %v: %v", name, err)
 724                 }
 725                 if info.parsed.Name.Name == "main" {
 726                         continue
 727                 }
 728                 if bytes.Contains(info.header, buildIgnore) {
 729                         continue
 730                 }
 731                 for _, imp := range info.imports {
 732                         path := imp.path
 733                         if !haveImport[path] {
 734                                 haveImport[path] = true
 735                                 imports = append(imports, path)
 736                         }
 737                 }
 738         }
 739         sort.Strings(imports)
 740         return imports, nil
 741 }
 742
 743 // depsPolicy returns a map m such that m[p][d] == true when p can import d.
 744 func depsPolicy(t *testing.T) *dag.Graph {
 745         g, err := dag.Parse(depsRules)
 746         if err != nil {
 747                 t.Fatal(err)
 748         }
 749         return g
 750 }
 751
 752 // TestStdlibLowercase tests that all standard library package names are
 753 // lowercase. See Issue 40065.
 754 func TestStdlibLowercase(t *testing.T) {
 755         if !testenv.HasSrc() {
 756                 t.Skipf("skipping on %s/%s, missing full GOROOT", runtime.GOOS, runtime.GOARCH)
 757         }
 758
 759         ctxt := Default
 760         all, err := listStdPkgs(ctxt.GOROOT)
 761         if err != nil {
 762                 t.Fatal(err)
 763         }
 764
 765         for _, pkgname := range all {
 766                 if strings.ToLower(pkgname) != pkgname {
 767                         t.Errorf("package %q should not use upper-case path", pkgname)
 768                 }
 769         }
 770 }
 771
 772 // TestFindImports tests that findImports works.  See #43249.
 773 func TestFindImports(t *testing.T) {
 774         imports, err := findImports("go/build")
 775         if err != nil {
 776                 t.Fatal(err)
 777         }
 778         t.Logf("go/build imports %q", imports)
 779         want := []string{"bytes", "os", "path/filepath", "strings"}
 780 wantLoop:
 781         for _, w := range want {
 782                 for _, imp := range imports {
 783                         if imp == w {
 784                                 continue wantLoop
 785                         }
 786                 }
 787                 t.Errorf("expected to find %q in import list", w)
 788         }
 789 }