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
 268         FMT
 269         < go/build/constraint, go/doc/comment;
 270
 271         go/internal/typeparams, go/build/constraint
 272         < go/parser;
 273
 274         go/doc/comment, go/parser, text/tabwriter
 275         < go/printer
 276         < go/format;
 277
 278         go/doc/comment, go/parser, internal/lazyregexp, text/template
 279         < go/doc;
 280
 281         math/big, go/token
 282         < go/constant;
 283
 284         container/heap, go/constant, go/parser, internal/types/errors, internal/lazyregexp
 285         < go/types;
 286
 287         FMT, internal/goexperiment
 288         < internal/buildcfg;
 289
 290         go/build/constraint, go/doc, go/parser, internal/buildcfg, internal/goroot, internal/goversion
 291         < go/build;
 292
 293         # databases
 294         FMT
 295         < database/sql/internal
 296         < database/sql/driver
 297         < database/sql;
 298
 299         # images
 300         FMT, compress/lzw, compress/zlib
 301         < image/color
 302         < image, image/color/palette
 303         < image/internal/imageutil
 304         < image/draw
 305         < image/gif, image/jpeg, image/png;
 306
 307         # cgo, delayed as long as possible.
 308         # If you add a dependency on CGO, you must add the package
 309         # to cgoPackages in cmd/dist/test.go as well.
 310         RUNTIME
 311         < C
 312         < runtime/cgo
 313         < CGO
 314         < runtime/msan, runtime/asan;
 315
 316         # runtime/race
 317         NONE < runtime/race/internal/amd64v1;
 318         NONE < runtime/race/internal/amd64v3;
 319         CGO, runtime/race/internal/amd64v1, runtime/race/internal/amd64v3 < runtime/race;
 320
 321         # Bulk of the standard library must not use cgo.
 322         # The prohibition stops at net and os/user.
 323         C !< fmt, go/types, CRYPTO-MATH, log/slog;
 324
 325         CGO, OS
 326         < plugin;
 327
 328         CGO, FMT
 329         < os/user
 330         < archive/tar;
 331
 332         sync
 333         < internal/singleflight;
 334
 335         os
 336         < golang.org/x/net/dns/dnsmessage,
 337           golang.org/x/net/lif,
 338           golang.org/x/net/route;
 339
 340         os, runtime, strconv, sync, unsafe,
 341         internal/godebug
 342         < internal/intern;
 343
 344         internal/bytealg, internal/intern, internal/itoa, math/bits, sort, strconv
 345         < net/netip;
 346
 347         # net is unavoidable when doing any networking,
 348         # so large dependencies must be kept out.
 349         # This is a long-looking list but most of these
 350         # are small with few dependencies.
 351         CGO,
 352         golang.org/x/net/dns/dnsmessage,
 353         golang.org/x/net/lif,
 354         golang.org/x/net/route,
 355         internal/godebug,
 356         internal/nettrace,
 357         internal/poll,
 358         internal/singleflight,
 359         internal/race,
 360         net/netip,
 361         os
 362         < net;
 363
 364         fmt, unicode !< net;
 365         math/rand !< net; # net uses runtime instead
 366
 367         # NET is net plus net-helper packages.
 368         FMT, net
 369         < net/textproto;
 370
 371         mime, net/textproto, net/url
 372         < NET;
 373
 374         # logging - most packages should not import; http and up is allowed
 375         FMT, log/internal
 376         < log;
 377
 378         log, log/slog !< crypto/tls, database/sql, go/importer, testing;
 379
 380         FMT, log, net
 381         < log/syslog;
 382
 383         RUNTIME
 384         < log/slog/internal, log/slog/internal/buffer;
 385
 386         FMT,
 387         encoding, encoding/json,
 388         log, log/internal,
 389         log/slog/internal, log/slog/internal/buffer,
 390         slices
 391         < log/slog
 392         < log/slog/internal/slogtest, log/slog/internal/benchmarks;
 393
 394         NET, log
 395         < net/mail;
 396
 397         NONE < crypto/internal/boring/sig, crypto/internal/boring/syso;
 398         sync/atomic < crypto/internal/boring/bcache, crypto/internal/boring/fipstls;
 399         crypto/internal/boring/sig, crypto/internal/boring/fipstls < crypto/tls/fipsonly;
 400
 401         # CRYPTO is core crypto algorithms - no cgo, fmt, net.
 402         # Unfortunately, stuck with reflect via encoding/binary.
 403         crypto/internal/boring/sig,
 404         crypto/internal/boring/syso,
 405         encoding/binary,
 406         golang.org/x/sys/cpu,
 407         hash, embed
 408         < crypto
 409         < crypto/subtle
 410         < crypto/internal/alias
 411         < crypto/cipher;
 412
 413         crypto/cipher,
 414         crypto/internal/boring/bcache
 415         < crypto/internal/boring
 416         < crypto/boring;
 417
 418         crypto/internal/alias
 419         < crypto/internal/randutil
 420         < crypto/internal/nistec/fiat
 421         < crypto/internal/nistec
 422         < crypto/internal/edwards25519/field
 423         < crypto/internal/edwards25519;
 424
 425         crypto/boring
 426         < crypto/aes, crypto/des, crypto/hmac, crypto/md5, crypto/rc4,
 427           crypto/sha1, crypto/sha256, crypto/sha512;
 428
 429         crypto/boring, crypto/internal/edwards25519/field
 430         < crypto/ecdh;
 431
 432         crypto/aes,
 433         crypto/des,
 434         crypto/ecdh,
 435         crypto/hmac,
 436         crypto/internal/edwards25519,
 437         crypto/md5,
 438         crypto/rc4,
 439         crypto/sha1,
 440         crypto/sha256,
 441         crypto/sha512
 442         < CRYPTO;
 443
 444         CGO, fmt, net !< CRYPTO;
 445
 446         # CRYPTO-MATH is core bignum-based crypto - no cgo, net; fmt now ok.
 447         CRYPTO, FMT, math/big
 448         < crypto/internal/boring/bbig
 449         < crypto/rand
 450         < crypto/ed25519
 451         < encoding/asn1
 452         < golang.org/x/crypto/cryptobyte/asn1
 453         < golang.org/x/crypto/cryptobyte
 454         < crypto/internal/bigmod
 455         < crypto/dsa, crypto/elliptic, crypto/rsa
 456         < crypto/ecdsa
 457         < CRYPTO-MATH;
 458
 459         CGO, net !< CRYPTO-MATH;
 460
 461         # TLS, Prince of Dependencies.
 462         CRYPTO-MATH, NET, container/list, encoding/hex, encoding/pem
 463         < golang.org/x/crypto/internal/alias
 464         < golang.org/x/crypto/internal/subtle
 465         < golang.org/x/crypto/chacha20
 466         < golang.org/x/crypto/internal/poly1305
 467         < golang.org/x/crypto/chacha20poly1305
 468         < golang.org/x/crypto/hkdf
 469         < crypto/x509/internal/macos
 470         < crypto/x509/pkix;
 471
 472         crypto/internal/boring/fipstls, crypto/x509/pkix
 473         < crypto/x509
 474         < crypto/tls;
 475
 476         # crypto-aware packages
 477
 478         DEBUG, go/build, go/types, text/scanner, crypto/md5
 479         < internal/pkgbits
 480         < go/internal/gcimporter, go/internal/gccgoimporter, go/internal/srcimporter
 481         < go/importer;
 482
 483         NET, crypto/rand, mime/quotedprintable
 484         < mime/multipart;
 485
 486         crypto/tls
 487         < net/smtp;
 488
 489         crypto/rand
 490         < hash/maphash; # for purego implementation
 491
 492         # HTTP, King of Dependencies.
 493
 494         FMT
 495         < golang.org/x/net/http2/hpack
 496         < net/http/internal, net/http/internal/ascii, net/http/internal/testcert;
 497
 498         FMT, NET, container/list, encoding/binary, log
 499         < golang.org/x/text/transform
 500         < golang.org/x/text/unicode/norm
 501         < golang.org/x/text/unicode/bidi
 502         < golang.org/x/text/secure/bidirule
 503         < golang.org/x/net/idna
 504         < golang.org/x/net/http/httpguts, golang.org/x/net/http/httpproxy;
 505
 506         NET, crypto/tls
 507         < net/http/httptrace;
 508
 509         compress/gzip,
 510         golang.org/x/net/http/httpguts,
 511         golang.org/x/net/http/httpproxy,
 512         golang.org/x/net/http2/hpack,
 513         net/http/internal,
 514         net/http/internal/ascii,
 515         net/http/internal/testcert,
 516         net/http/httptrace,
 517         mime/multipart,
 518         log
 519         < net/http;
 520
 521         # HTTP-aware packages
 522
 523         encoding/json, net/http
 524         < expvar;
 525
 526         net/http, net/http/internal/ascii
 527         < net/http/cookiejar, net/http/httputil;
 528
 529         net/http, flag
 530         < net/http/httptest;
 531
 532         net/http, regexp
 533         < net/http/cgi
 534         < net/http/fcgi;
 535
 536         # Profiling
 537         FMT, compress/gzip, encoding/binary, text/tabwriter
 538         < runtime/pprof;
 539
 540         OS, compress/gzip, internal/lazyregexp
 541         < internal/profile;
 542
 543         html, internal/profile, net/http, runtime/pprof, runtime/trace
 544         < net/http/pprof;
 545
 546         # RPC
 547         encoding/gob, encoding/json, go/token, html/template, net/http
 548         < net/rpc
 549         < net/rpc/jsonrpc;
 550
 551         # System Information
 552         internal/cpu, sync
 553         < internal/sysinfo;
 554
 555         # Test-only
 556         log
 557         < testing/iotest
 558         < testing/fstest;
 559
 560         FMT, flag, math/rand
 561         < testing/quick;
 562
 563         FMT, DEBUG, flag, runtime/trace, internal/sysinfo, math/rand
 564         < testing;
 565
 566         FMT, crypto/sha256, encoding/json, go/ast, go/parser, go/token,
 567         internal/godebug, math/rand, encoding/hex, crypto/sha256
 568         < internal/fuzz;
 569
 570         internal/fuzz, internal/testlog, runtime/pprof, regexp
 571         < testing/internal/testdeps;
 572
 573         OS, flag, testing, internal/cfg, internal/platform, internal/goroot
 574         < internal/testenv;
 575
 576         OS, encoding/base64
 577         < internal/obscuretestdata;
 578
 579         CGO, OS, fmt
 580         < internal/testpty;
 581
 582         NET, testing, math/rand
 583         < golang.org/x/net/nettest;
 584
 585         syscall
 586         < os/exec/internal/fdtest;
 587
 588         FMT, container/heap, math/rand
 589         < internal/trace;
 590
 591         FMT
 592         < internal/diff, internal/txtar;
 593
 594         FMT, crypto/md5, encoding/binary, regexp, sort, text/tabwriter, unsafe,
 595         internal/coverage, internal/coverage/uleb128
 596         < internal/coverage/cmerge,
 597           internal/coverage/pods,
 598           internal/coverage/slicereader,
 599           internal/coverage/slicewriter;
 600
 601         internal/coverage/slicereader, internal/coverage/slicewriter
 602         < internal/coverage/stringtab
 603         < internal/coverage/decodecounter, internal/coverage/decodemeta,
 604           internal/coverage/encodecounter, internal/coverage/encodemeta;
 605
 606         internal/coverage/cmerge
 607         < internal/coverage/cformat;
 608
 609         runtime/debug,
 610         internal/coverage/calloc,
 611         internal/coverage/cformat,
 612         internal/coverage/decodecounter, internal/coverage/decodemeta,
 613         internal/coverage/encodecounter, internal/coverage/encodemeta,
 614         internal/coverage/pods
 615         < runtime/coverage;
 616 `
 617
 618 // listStdPkgs returns the same list of packages as "go list std".
 619 func listStdPkgs(goroot string) ([]string, error) {
 620         // Based on cmd/go's matchPackages function.
 621         var pkgs []string
 622
 623         src := filepath.Join(goroot, "src") + string(filepath.Separator)
 624         walkFn := func(path string, d fs.DirEntry, err error) error {
 625                 if err != nil || !d.IsDir() || path == src {
 626                         return nil
 627                 }
 628
 629                 base := filepath.Base(path)
 630                 if strings.HasPrefix(base, ".") || strings.HasPrefix(base, "_") || base == "testdata" {
 631                         return filepath.SkipDir
 632                 }
 633
 634                 name := filepath.ToSlash(path[len(src):])
 635                 if name == "builtin" || name == "cmd" {
 636                         return filepath.SkipDir
 637                 }
 638
 639                 pkgs = append(pkgs, strings.TrimPrefix(name, "vendor/"))
 640                 return nil
 641         }
 642         if err := filepath.WalkDir(src, walkFn); err != nil {
 643                 return nil, err
 644         }
 645         return pkgs, nil
 646 }
 647
 648 func TestDependencies(t *testing.T) {
 649         if !testenv.HasSrc() {
 650                 // Tests run in a limited file system and we do not
 651                 // provide access to every source file.
 652                 t.Skipf("skipping on %s/%s, missing full GOROOT", runtime.GOOS, runtime.GOARCH)
 653         }
 654
 655         ctxt := Default
 656         all, err := listStdPkgs(ctxt.GOROOT)
 657         if err != nil {
 658                 t.Fatal(err)
 659         }
 660         sort.Strings(all)
 661
 662         sawImport := map[string]map[string]bool{} // from package => to package => true
 663         policy := depsPolicy(t)
 664
 665         for _, pkg := range all {
 666                 imports, err := findImports(pkg)
 667                 if err != nil {
 668                         t.Error(err)
 669                         continue
 670                 }
 671                 if sawImport[pkg] == nil {
 672                         sawImport[pkg] = map[string]bool{}
 673                 }
 674                 var bad []string
 675                 for _, imp := range imports {
 676                         sawImport[pkg][imp] = true
 677                         if !policy.HasEdge(pkg, imp) {
 678                                 bad = append(bad, imp)
 679                         }
 680                 }
 681                 if bad != nil {
 682                         t.Errorf("unexpected dependency: %s imports %v", pkg, bad)
 683                 }
 684         }
 685 }
 686
 687 var buildIgnore = []byte("\n//go:build ignore")
 688
 689 func findImports(pkg string) ([]string, error) {
 690         vpkg := pkg
 691         if strings.HasPrefix(pkg, "golang.org") {
 692                 vpkg = "vendor/" + pkg
 693         }
 694         dir := filepath.Join(Default.GOROOT, "src", vpkg)
 695         files, err := os.ReadDir(dir)
 696         if err != nil {
 697                 return nil, err
 698         }
 699         var imports []string
 700         var haveImport = map[string]bool{}
 701         if pkg == "crypto/internal/boring" {
 702                 haveImport["C"] = true // kludge: prevent C from appearing in crypto/internal/boring imports
 703         }
 704         fset := token.NewFileSet()
 705         for _, file := range files {
 706                 name := file.Name()
 707                 if name == "slice_go14.go" || name == "slice_go18.go" {
 708                         // These files are for compiler bootstrap with older versions of Go and not built in the standard build.
 709                         continue
 710                 }
 711                 if !strings.HasSuffix(name, ".go") || strings.HasSuffix(name, "_test.go") {
 712                         continue
 713                 }
 714                 info := fileInfo{
 715                         name: filepath.Join(dir, name),
 716                         fset: fset,
 717                 }
 718                 f, err := os.Open(info.name)
 719                 if err != nil {
 720                         return nil, err
 721                 }
 722                 err = readGoInfo(f, &info)
 723                 f.Close()
 724                 if err != nil {
 725                         return nil, fmt.Errorf("reading %v: %v", name, err)
 726                 }
 727                 if info.parsed.Name.Name == "main" {
 728                         continue
 729                 }
 730                 if bytes.Contains(info.header, buildIgnore) {
 731                         continue
 732                 }
 733                 for _, imp := range info.imports {
 734                         path := imp.path
 735                         if !haveImport[path] {
 736                                 haveImport[path] = true
 737                                 imports = append(imports, path)
 738                         }
 739                 }
 740         }
 741         sort.Strings(imports)
 742         return imports, nil
 743 }
 744
 745 // depsPolicy returns a map m such that m[p][d] == true when p can import d.
 746 func depsPolicy(t *testing.T) *dag.Graph {
 747         g, err := dag.Parse(depsRules)
 748         if err != nil {
 749                 t.Fatal(err)
 750         }
 751         return g
 752 }
 753
 754 // TestStdlibLowercase tests that all standard library package names are
 755 // lowercase. See Issue 40065.
 756 func TestStdlibLowercase(t *testing.T) {
 757         if !testenv.HasSrc() {
 758                 t.Skipf("skipping on %s/%s, missing full GOROOT", runtime.GOOS, runtime.GOARCH)
 759         }
 760
 761         ctxt := Default
 762         all, err := listStdPkgs(ctxt.GOROOT)
 763         if err != nil {
 764                 t.Fatal(err)
 765         }
 766
 767         for _, pkgname := range all {
 768                 if strings.ToLower(pkgname) != pkgname {
 769                         t.Errorf("package %q should not use upper-case path", pkgname)
 770                 }
 771         }
 772 }
 773
 774 // TestFindImports tests that findImports works.  See #43249.
 775 func TestFindImports(t *testing.T) {
 776         imports, err := findImports("go/build")
 777         if err != nil {
 778                 t.Fatal(err)
 779         }
 780         t.Logf("go/build imports %q", imports)
 781         want := []string{"bytes", "os", "path/filepath", "strings"}
 782 wantLoop:
 783         for _, w := range want {
 784                 for _, imp := range imports {
 785                         if imp == w {
 786                                 continue wantLoop
 787                         }
 788                 }
 789                 t.Errorf("expected to find %q in import list", w)
 790         }
 791 }