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