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         math/big, go/token
 279         < go/constant;
 280
 281         container/heap, go/constant, go/parser, internal/types/errors
 282         < go/types;
 283
 284         # The vast majority of standard library packages should not be resorting to regexp.
 285         # go/types is a good chokepoint. It shouldn't use regexp, nor should anything
 286         # that is low-enough level to be used by go/types.
 287         regexp !< go/types;
 288
 289         go/doc/comment, go/parser, internal/lazyregexp, text/template
 290         < go/doc;
 291
 292         FMT, internal/goexperiment
 293         < internal/buildcfg;
 294
 295         go/build/constraint, go/doc, go/parser, internal/buildcfg, internal/goroot, internal/goversion
 296         < go/build;
 297
 298         # databases
 299         FMT
 300         < database/sql/internal
 301         < database/sql/driver
 302         < database/sql;
 303
 304         # images
 305         FMT, compress/lzw, compress/zlib
 306         < image/color
 307         < image, image/color/palette
 308         < image/internal/imageutil
 309         < image/draw
 310         < image/gif, image/jpeg, image/png;
 311
 312         # cgo, delayed as long as possible.
 313         # If you add a dependency on CGO, you must add the package
 314         # to cgoPackages in cmd/dist/test.go as well.
 315         RUNTIME
 316         < C
 317         < runtime/cgo
 318         < CGO
 319         < runtime/msan, runtime/asan;
 320
 321         # runtime/race
 322         NONE < runtime/race/internal/amd64v1;
 323         NONE < runtime/race/internal/amd64v3;
 324         CGO, runtime/race/internal/amd64v1, runtime/race/internal/amd64v3 < runtime/race;
 325
 326         # Bulk of the standard library must not use cgo.
 327         # The prohibition stops at net and os/user.
 328         C !< fmt, go/types, CRYPTO-MATH, log/slog;
 329
 330         CGO, OS
 331         < plugin;
 332
 333         CGO, FMT
 334         < os/user
 335         < archive/tar;
 336
 337         sync
 338         < internal/singleflight;
 339
 340         os
 341         < golang.org/x/net/dns/dnsmessage,
 342           golang.org/x/net/lif,
 343           golang.org/x/net/route;
 344
 345         os, runtime, strconv, sync, unsafe,
 346         internal/godebug
 347         < internal/intern;
 348
 349         internal/bytealg, internal/intern, internal/itoa, math/bits, sort, strconv
 350         < net/netip;
 351
 352         # net is unavoidable when doing any networking,
 353         # so large dependencies must be kept out.
 354         # This is a long-looking list but most of these
 355         # are small with few dependencies.
 356         CGO,
 357         golang.org/x/net/dns/dnsmessage,
 358         golang.org/x/net/lif,
 359         golang.org/x/net/route,
 360         internal/godebug,
 361         internal/nettrace,
 362         internal/poll,
 363         internal/singleflight,
 364         internal/race,
 365         net/netip,
 366         os
 367         < net;
 368
 369         fmt, unicode !< net;
 370         math/rand !< net; # net uses runtime instead
 371
 372         # NET is net plus net-helper packages.
 373         FMT, net
 374         < net/textproto;
 375
 376         mime, net/textproto, net/url
 377         < NET;
 378
 379         # logging - most packages should not import; http and up is allowed
 380         FMT, log/internal
 381         < log;
 382
 383         log, log/slog !< crypto/tls, database/sql, go/importer, testing;
 384
 385         FMT, log, net
 386         < log/syslog;
 387
 388         RUNTIME
 389         < log/slog/internal, log/slog/internal/buffer;
 390
 391         FMT,
 392         encoding, encoding/json,
 393         log, log/internal,
 394         log/slog/internal, log/slog/internal/buffer,
 395         slices
 396         < log/slog
 397         < log/slog/internal/slogtest, log/slog/internal/benchmarks;
 398
 399         NET, log
 400         < net/mail;
 401
 402         NONE < crypto/internal/boring/sig, crypto/internal/boring/syso;
 403         sync/atomic < crypto/internal/boring/bcache, crypto/internal/boring/fipstls;
 404         crypto/internal/boring/sig, crypto/internal/boring/fipstls < crypto/tls/fipsonly;
 405
 406         # CRYPTO is core crypto algorithms - no cgo, fmt, net.
 407         # Unfortunately, stuck with reflect via encoding/binary.
 408         crypto/internal/boring/sig,
 409         crypto/internal/boring/syso,
 410         encoding/binary,
 411         golang.org/x/sys/cpu,
 412         hash, embed
 413         < crypto
 414         < crypto/subtle
 415         < crypto/internal/alias
 416         < crypto/cipher;
 417
 418         crypto/cipher,
 419         crypto/internal/boring/bcache
 420         < crypto/internal/boring
 421         < crypto/boring;
 422
 423         crypto/internal/alias
 424         < crypto/internal/randutil
 425         < crypto/internal/nistec/fiat
 426         < crypto/internal/nistec
 427         < crypto/internal/edwards25519/field
 428         < crypto/internal/edwards25519;
 429
 430         crypto/boring
 431         < crypto/aes, crypto/des, crypto/hmac, crypto/md5, crypto/rc4,
 432           crypto/sha1, crypto/sha256, crypto/sha512;
 433
 434         crypto/boring, crypto/internal/edwards25519/field
 435         < crypto/ecdh;
 436
 437         crypto/aes,
 438         crypto/des,
 439         crypto/ecdh,
 440         crypto/hmac,
 441         crypto/internal/edwards25519,
 442         crypto/md5,
 443         crypto/rc4,
 444         crypto/sha1,
 445         crypto/sha256,
 446         crypto/sha512
 447         < CRYPTO;
 448
 449         CGO, fmt, net !< CRYPTO;
 450
 451         # CRYPTO-MATH is core bignum-based crypto - no cgo, net; fmt now ok.
 452         CRYPTO, FMT, math/big
 453         < crypto/internal/boring/bbig
 454         < crypto/rand
 455         < crypto/ed25519
 456         < encoding/asn1
 457         < golang.org/x/crypto/cryptobyte/asn1
 458         < golang.org/x/crypto/cryptobyte
 459         < crypto/internal/bigmod
 460         < crypto/dsa, crypto/elliptic, crypto/rsa
 461         < crypto/ecdsa
 462         < CRYPTO-MATH;
 463
 464         CGO, net !< CRYPTO-MATH;
 465
 466         # TLS, Prince of Dependencies.
 467         CRYPTO-MATH, NET, container/list, encoding/hex, encoding/pem
 468         < golang.org/x/crypto/internal/alias
 469         < golang.org/x/crypto/internal/subtle
 470         < golang.org/x/crypto/chacha20
 471         < golang.org/x/crypto/internal/poly1305
 472         < golang.org/x/crypto/chacha20poly1305
 473         < golang.org/x/crypto/hkdf
 474         < crypto/x509/internal/macos
 475         < crypto/x509/pkix;
 476
 477         crypto/internal/boring/fipstls, crypto/x509/pkix
 478         < crypto/x509
 479         < crypto/tls;
 480
 481         # crypto-aware packages
 482
 483         DEBUG, go/build, go/types, text/scanner, crypto/md5
 484         < internal/pkgbits
 485         < go/internal/gcimporter, go/internal/gccgoimporter, go/internal/srcimporter
 486         < go/importer;
 487
 488         NET, crypto/rand, mime/quotedprintable
 489         < mime/multipart;
 490
 491         crypto/tls
 492         < net/smtp;
 493
 494         crypto/rand
 495         < hash/maphash; # for purego implementation
 496
 497         # HTTP, King of Dependencies.
 498
 499         FMT
 500         < golang.org/x/net/http2/hpack
 501         < net/http/internal, net/http/internal/ascii, net/http/internal/testcert;
 502
 503         FMT, NET, container/list, encoding/binary, log
 504         < golang.org/x/text/transform
 505         < golang.org/x/text/unicode/norm
 506         < golang.org/x/text/unicode/bidi
 507         < golang.org/x/text/secure/bidirule
 508         < golang.org/x/net/idna
 509         < golang.org/x/net/http/httpguts, golang.org/x/net/http/httpproxy;
 510
 511         NET, crypto/tls
 512         < net/http/httptrace;
 513
 514         compress/gzip,
 515         golang.org/x/net/http/httpguts,
 516         golang.org/x/net/http/httpproxy,
 517         golang.org/x/net/http2/hpack,
 518         net/http/internal,
 519         net/http/internal/ascii,
 520         net/http/internal/testcert,
 521         net/http/httptrace,
 522         mime/multipart,
 523         log
 524         < net/http;
 525
 526         # HTTP-aware packages
 527
 528         encoding/json, net/http
 529         < expvar;
 530
 531         net/http, net/http/internal/ascii
 532         < net/http/cookiejar, net/http/httputil;
 533
 534         net/http, flag
 535         < net/http/httptest;
 536
 537         net/http, regexp
 538         < net/http/cgi
 539         < net/http/fcgi;
 540
 541         # Profiling
 542         FMT, compress/gzip, encoding/binary, text/tabwriter
 543         < runtime/pprof;
 544
 545         OS, compress/gzip, internal/lazyregexp
 546         < internal/profile;
 547
 548         html, internal/profile, net/http, runtime/pprof, runtime/trace
 549         < net/http/pprof;
 550
 551         # RPC
 552         encoding/gob, encoding/json, go/token, html/template, net/http
 553         < net/rpc
 554         < net/rpc/jsonrpc;
 555
 556         # System Information
 557         internal/cpu, sync
 558         < internal/sysinfo;
 559
 560         # Test-only
 561         log
 562         < testing/iotest
 563         < testing/fstest;
 564
 565         FMT, flag, math/rand
 566         < testing/quick;
 567
 568         FMT, DEBUG, flag, runtime/trace, internal/sysinfo, math/rand
 569         < testing;
 570
 571         FMT, crypto/sha256, encoding/json, go/ast, go/parser, go/token,
 572         internal/godebug, math/rand, encoding/hex, crypto/sha256
 573         < internal/fuzz;
 574
 575         internal/fuzz, internal/testlog, runtime/pprof, regexp
 576         < testing/internal/testdeps;
 577
 578         OS, flag, testing, internal/cfg, internal/platform, internal/goroot
 579         < internal/testenv;
 580
 581         OS, encoding/base64
 582         < internal/obscuretestdata;
 583
 584         CGO, OS, fmt
 585         < internal/testpty;
 586
 587         NET, testing, math/rand
 588         < golang.org/x/net/nettest;
 589
 590         syscall
 591         < os/exec/internal/fdtest;
 592
 593         FMT, container/heap, math/rand
 594         < internal/trace;
 595
 596         FMT
 597         < internal/diff, internal/txtar;
 598
 599         FMT, crypto/md5, encoding/binary, regexp, sort, text/tabwriter, unsafe,
 600         internal/coverage, internal/coverage/uleb128
 601         < internal/coverage/cmerge,
 602           internal/coverage/pods,
 603           internal/coverage/slicereader,
 604           internal/coverage/slicewriter;
 605
 606         internal/coverage/slicereader, internal/coverage/slicewriter
 607         < internal/coverage/stringtab
 608         < internal/coverage/decodecounter, internal/coverage/decodemeta,
 609           internal/coverage/encodecounter, internal/coverage/encodemeta;
 610
 611         internal/coverage/cmerge
 612         < internal/coverage/cformat;
 613
 614         runtime/debug,
 615         internal/coverage/calloc,
 616         internal/coverage/cformat,
 617         internal/coverage/decodecounter, internal/coverage/decodemeta,
 618         internal/coverage/encodecounter, internal/coverage/encodemeta,
 619         internal/coverage/pods
 620         < runtime/coverage;
 621 `
 622
 623 // listStdPkgs returns the same list of packages as "go list std".
 624 func listStdPkgs(goroot string) ([]string, error) {
 625         // Based on cmd/go's matchPackages function.
 626         var pkgs []string
 627
 628         src := filepath.Join(goroot, "src") + string(filepath.Separator)
 629         walkFn := func(path string, d fs.DirEntry, err error) error {
 630                 if err != nil || !d.IsDir() || path == src {
 631                         return nil
 632                 }
 633
 634                 base := filepath.Base(path)
 635                 if strings.HasPrefix(base, ".") || strings.HasPrefix(base, "_") || base == "testdata" {
 636                         return filepath.SkipDir
 637                 }
 638
 639                 name := filepath.ToSlash(path[len(src):])
 640                 if name == "builtin" || name == "cmd" {
 641                         return filepath.SkipDir
 642                 }
 643
 644                 pkgs = append(pkgs, strings.TrimPrefix(name, "vendor/"))
 645                 return nil
 646         }
 647         if err := filepath.WalkDir(src, walkFn); err != nil {
 648                 return nil, err
 649         }
 650         return pkgs, nil
 651 }
 652
 653 func TestDependencies(t *testing.T) {
 654         if !testenv.HasSrc() {
 655                 // Tests run in a limited file system and we do not
 656                 // provide access to every source file.
 657                 t.Skipf("skipping on %s/%s, missing full GOROOT", runtime.GOOS, runtime.GOARCH)
 658         }
 659
 660         ctxt := Default
 661         all, err := listStdPkgs(ctxt.GOROOT)
 662         if err != nil {
 663                 t.Fatal(err)
 664         }
 665         sort.Strings(all)
 666
 667         sawImport := map[string]map[string]bool{} // from package => to package => true
 668         policy := depsPolicy(t)
 669
 670         for _, pkg := range all {
 671                 imports, err := findImports(pkg)
 672                 if err != nil {
 673                         t.Error(err)
 674                         continue
 675                 }
 676                 if sawImport[pkg] == nil {
 677                         sawImport[pkg] = map[string]bool{}
 678                 }
 679                 var bad []string
 680                 for _, imp := range imports {
 681                         sawImport[pkg][imp] = true
 682                         if !policy.HasEdge(pkg, imp) {
 683                                 bad = append(bad, imp)
 684                         }
 685                 }
 686                 if bad != nil {
 687                         t.Errorf("unexpected dependency: %s imports %v", pkg, bad)
 688                 }
 689         }
 690 }
 691
 692 var buildIgnore = []byte("\n//go:build ignore")
 693
 694 func findImports(pkg string) ([]string, error) {
 695         vpkg := pkg
 696         if strings.HasPrefix(pkg, "golang.org") {
 697                 vpkg = "vendor/" + pkg
 698         }
 699         dir := filepath.Join(Default.GOROOT, "src", vpkg)
 700         files, err := os.ReadDir(dir)
 701         if err != nil {
 702                 return nil, err
 703         }
 704         var imports []string
 705         var haveImport = map[string]bool{}
 706         if pkg == "crypto/internal/boring" {
 707                 haveImport["C"] = true // kludge: prevent C from appearing in crypto/internal/boring imports
 708         }
 709         fset := token.NewFileSet()
 710         for _, file := range files {
 711                 name := file.Name()
 712                 if name == "slice_go14.go" || name == "slice_go18.go" {
 713                         // These files are for compiler bootstrap with older versions of Go and not built in the standard build.
 714                         continue
 715                 }
 716                 if !strings.HasSuffix(name, ".go") || strings.HasSuffix(name, "_test.go") {
 717                         continue
 718                 }
 719                 info := fileInfo{
 720                         name: filepath.Join(dir, name),
 721                         fset: fset,
 722                 }
 723                 f, err := os.Open(info.name)
 724                 if err != nil {
 725                         return nil, err
 726                 }
 727                 err = readGoInfo(f, &info)
 728                 f.Close()
 729                 if err != nil {
 730                         return nil, fmt.Errorf("reading %v: %v", name, err)
 731                 }
 732                 if info.parsed.Name.Name == "main" {
 733                         continue
 734                 }
 735                 if bytes.Contains(info.header, buildIgnore) {
 736                         continue
 737                 }
 738                 for _, imp := range info.imports {
 739                         path := imp.path
 740                         if !haveImport[path] {
 741                                 haveImport[path] = true
 742                                 imports = append(imports, path)
 743                         }
 744                 }
 745         }
 746         sort.Strings(imports)
 747         return imports, nil
 748 }
 749
 750 // depsPolicy returns a map m such that m[p][d] == true when p can import d.
 751 func depsPolicy(t *testing.T) *dag.Graph {
 752         g, err := dag.Parse(depsRules)
 753         if err != nil {
 754                 t.Fatal(err)
 755         }
 756         return g
 757 }
 758
 759 // TestStdlibLowercase tests that all standard library package names are
 760 // lowercase. See Issue 40065.
 761 func TestStdlibLowercase(t *testing.T) {
 762         if !testenv.HasSrc() {
 763                 t.Skipf("skipping on %s/%s, missing full GOROOT", runtime.GOOS, runtime.GOARCH)
 764         }
 765
 766         ctxt := Default
 767         all, err := listStdPkgs(ctxt.GOROOT)
 768         if err != nil {
 769                 t.Fatal(err)
 770         }
 771
 772         for _, pkgname := range all {
 773                 if strings.ToLower(pkgname) != pkgname {
 774                         t.Errorf("package %q should not use upper-case path", pkgname)
 775                 }
 776         }
 777 }
 778
 779 // TestFindImports tests that findImports works.  See #43249.
 780 func TestFindImports(t *testing.T) {
 781         imports, err := findImports("go/build")
 782         if err != nil {
 783                 t.Fatal(err)
 784         }
 785         t.Logf("go/build imports %q", imports)
 786         want := []string{"bytes", "os", "path/filepath", "strings"}
 787 wantLoop:
 788         for _, w := range want {
 789                 for _, imp := range imports {
 790                         if imp == w {
 791                                 continue wantLoop
 792                         }
 793                 }
 794                 t.Errorf("expected to find %q in import list", w)
 795         }
 796 }