Source file 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  	  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, hash/maphash;
   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, regexp
   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;
   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 !< crypto/tls, database/sql, go/importer, testing;
   376  
   377  	FMT, log, net
   378  	< log/syslog;
   379  
   380  	NET, log
   381  	< net/mail;
   382  
   383  	NONE < crypto/internal/boring/sig, crypto/internal/boring/syso;
   384  	sync/atomic < crypto/internal/boring/bcache, crypto/internal/boring/fipstls;
   385  	crypto/internal/boring/sig, crypto/internal/boring/fipstls < crypto/tls/fipsonly;
   386  
   387  	# CRYPTO is core crypto algorithms - no cgo, fmt, net.
   388  	# Unfortunately, stuck with reflect via encoding/binary.
   389  	crypto/internal/boring/sig,
   390  	crypto/internal/boring/syso,
   391  	encoding/binary,
   392  	golang.org/x/sys/cpu,
   393  	hash, embed
   394  	< crypto
   395  	< crypto/subtle
   396  	< crypto/internal/alias
   397  	< crypto/cipher;
   398  
   399  	crypto/cipher,
   400  	crypto/internal/boring/bcache
   401  	< crypto/internal/boring
   402  	< crypto/boring;
   403  
   404  	crypto/internal/alias
   405  	< crypto/internal/randutil
   406  	< crypto/internal/nistec/fiat
   407  	< crypto/internal/nistec
   408  	< crypto/internal/edwards25519/field
   409  	< crypto/internal/edwards25519;
   410  
   411  	crypto/boring
   412  	< crypto/aes, crypto/des, crypto/hmac, crypto/md5, crypto/rc4,
   413  	  crypto/sha1, crypto/sha256, crypto/sha512;
   414  
   415  	crypto/boring, crypto/internal/edwards25519/field
   416  	< crypto/ecdh;
   417  
   418  	crypto/aes,
   419  	crypto/des,
   420  	crypto/ecdh,
   421  	crypto/hmac,
   422  	crypto/internal/edwards25519,
   423  	crypto/md5,
   424  	crypto/rc4,
   425  	crypto/sha1,
   426  	crypto/sha256,
   427  	crypto/sha512
   428  	< CRYPTO;
   429  
   430  	CGO, fmt, net !< CRYPTO;
   431  
   432  	# CRYPTO-MATH is core bignum-based crypto - no cgo, net; fmt now ok.
   433  	CRYPTO, FMT, math/big
   434  	< crypto/internal/boring/bbig
   435  	< crypto/rand
   436  	< crypto/ed25519
   437  	< encoding/asn1
   438  	< golang.org/x/crypto/cryptobyte/asn1
   439  	< golang.org/x/crypto/cryptobyte
   440  	< crypto/internal/bigmod
   441  	< crypto/dsa, crypto/elliptic, crypto/rsa
   442  	< crypto/ecdsa
   443  	< CRYPTO-MATH;
   444  
   445  	CGO, net !< CRYPTO-MATH;
   446  
   447  	# TLS, Prince of Dependencies.
   448  	CRYPTO-MATH, NET, container/list, encoding/hex, encoding/pem
   449  	< golang.org/x/crypto/internal/alias
   450  	< golang.org/x/crypto/internal/subtle
   451  	< golang.org/x/crypto/chacha20
   452  	< golang.org/x/crypto/internal/poly1305
   453  	< golang.org/x/crypto/chacha20poly1305
   454  	< golang.org/x/crypto/hkdf
   455  	< crypto/x509/internal/macos
   456  	< crypto/x509/pkix;
   457  
   458  	crypto/internal/boring/fipstls, crypto/x509/pkix
   459  	< crypto/x509
   460  	< crypto/tls;
   461  
   462  	# crypto-aware packages
   463  
   464  	DEBUG, go/build, go/types, text/scanner, crypto/md5
   465  	< internal/pkgbits
   466  	< go/internal/gcimporter, go/internal/gccgoimporter, go/internal/srcimporter
   467  	< go/importer;
   468  
   469  	NET, crypto/rand, mime/quotedprintable
   470  	< mime/multipart;
   471  
   472  	crypto/tls
   473  	< net/smtp;
   474  
   475  	# HTTP, King of Dependencies.
   476  
   477  	FMT
   478  	< golang.org/x/net/http2/hpack
   479  	< net/http/internal, net/http/internal/ascii, net/http/internal/testcert;
   480  
   481  	FMT, NET, container/list, encoding/binary, log
   482  	< golang.org/x/text/transform
   483  	< golang.org/x/text/unicode/norm
   484  	< golang.org/x/text/unicode/bidi
   485  	< golang.org/x/text/secure/bidirule
   486  	< golang.org/x/net/idna
   487  	< golang.org/x/net/http/httpguts, golang.org/x/net/http/httpproxy;
   488  
   489  	NET, crypto/tls
   490  	< net/http/httptrace;
   491  
   492  	compress/gzip,
   493  	golang.org/x/net/http/httpguts,
   494  	golang.org/x/net/http/httpproxy,
   495  	golang.org/x/net/http2/hpack,
   496  	net/http/internal,
   497  	net/http/internal/ascii,
   498  	net/http/internal/testcert,
   499  	net/http/httptrace,
   500  	mime/multipart,
   501  	log
   502  	< net/http;
   503  
   504  	# HTTP-aware packages
   505  
   506  	encoding/json, net/http
   507  	< expvar;
   508  
   509  	net/http, net/http/internal/ascii
   510  	< net/http/cookiejar, net/http/httputil;
   511  
   512  	net/http, flag
   513  	< net/http/httptest;
   514  
   515  	net/http, regexp
   516  	< net/http/cgi
   517  	< net/http/fcgi;
   518  
   519  	# Profiling
   520  	FMT, compress/gzip, encoding/binary, text/tabwriter
   521  	< runtime/pprof;
   522  
   523  	OS, compress/gzip, regexp
   524  	< internal/profile;
   525  
   526  	html, internal/profile, net/http, runtime/pprof, runtime/trace
   527  	< net/http/pprof;
   528  
   529  	# RPC
   530  	encoding/gob, encoding/json, go/token, html/template, net/http
   531  	< net/rpc
   532  	< net/rpc/jsonrpc;
   533  
   534  	# System Information
   535  	internal/cpu, sync
   536  	< internal/sysinfo;
   537  
   538  	# Test-only
   539  	log
   540  	< testing/iotest
   541  	< testing/fstest;
   542  
   543  	FMT, flag, math/rand
   544  	< testing/quick;
   545  
   546  	FMT, DEBUG, flag, runtime/trace, internal/sysinfo, math/rand
   547  	< testing;
   548  
   549  	FMT, crypto/sha256, encoding/json, go/ast, go/parser, go/token,
   550  	internal/godebug, math/rand, encoding/hex, crypto/sha256
   551  	< internal/fuzz;
   552  
   553  	internal/fuzz, internal/testlog, runtime/pprof, regexp
   554  	< testing/internal/testdeps;
   555  
   556  	OS, flag, testing, internal/cfg, internal/platform, internal/goroot
   557  	< internal/testenv;
   558  
   559  	OS, encoding/base64
   560  	< internal/obscuretestdata;
   561  
   562  	CGO, OS, fmt
   563  	< internal/testpty;
   564  
   565  	NET, testing, math/rand
   566  	< golang.org/x/net/nettest;
   567  
   568  	syscall
   569  	< os/exec/internal/fdtest;
   570  
   571  	FMT, container/heap, math/rand
   572  	< internal/trace;
   573  
   574  	FMT
   575  	< internal/diff, internal/txtar;
   576  
   577  	FMT, crypto/md5, encoding/binary, regexp, sort, text/tabwriter, unsafe,
   578  	internal/coverage, internal/coverage/uleb128
   579  	< internal/coverage/cmerge,
   580  	  internal/coverage/pods,
   581  	  internal/coverage/slicereader,
   582  	  internal/coverage/slicewriter;
   583  
   584  	internal/coverage/slicereader, internal/coverage/slicewriter
   585  	< internal/coverage/stringtab
   586  	< internal/coverage/decodecounter, internal/coverage/decodemeta,
   587  	  internal/coverage/encodecounter, internal/coverage/encodemeta;
   588  
   589  	internal/coverage/cmerge
   590  	< internal/coverage/cformat;
   591  
   592  	runtime/debug,
   593  	internal/coverage/calloc,
   594  	internal/coverage/cformat,
   595  	internal/coverage/decodecounter, internal/coverage/decodemeta,
   596  	internal/coverage/encodecounter, internal/coverage/encodemeta,
   597  	internal/coverage/pods
   598  	< runtime/coverage;
   599  `
   600  
   601  // listStdPkgs returns the same list of packages as "go list std".
   602  func listStdPkgs(goroot string) ([]string, error) {
   603  	// Based on cmd/go's matchPackages function.
   604  	var pkgs []string
   605  
   606  	src := filepath.Join(goroot, "src") + string(filepath.Separator)
   607  	walkFn := func(path string, d fs.DirEntry, err error) error {
   608  		if err != nil || !d.IsDir() || path == src {
   609  			return nil
   610  		}
   611  
   612  		base := filepath.Base(path)
   613  		if strings.HasPrefix(base, ".") || strings.HasPrefix(base, "_") || base == "testdata" {
   614  			return filepath.SkipDir
   615  		}
   616  
   617  		name := filepath.ToSlash(path[len(src):])
   618  		if name == "builtin" || name == "cmd" {
   619  			return filepath.SkipDir
   620  		}
   621  
   622  		pkgs = append(pkgs, strings.TrimPrefix(name, "vendor/"))
   623  		return nil
   624  	}
   625  	if err := filepath.WalkDir(src, walkFn); err != nil {
   626  		return nil, err
   627  	}
   628  	return pkgs, nil
   629  }
   630  
   631  func TestDependencies(t *testing.T) {
   632  	if !testenv.HasSrc() {
   633  		// Tests run in a limited file system and we do not
   634  		// provide access to every source file.
   635  		t.Skipf("skipping on %s/%s, missing full GOROOT", runtime.GOOS, runtime.GOARCH)
   636  	}
   637  
   638  	ctxt := Default
   639  	all, err := listStdPkgs(ctxt.GOROOT)
   640  	if err != nil {
   641  		t.Fatal(err)
   642  	}
   643  	sort.Strings(all)
   644  
   645  	sawImport := map[string]map[string]bool{} // from package => to package => true
   646  	policy := depsPolicy(t)
   647  
   648  	for _, pkg := range all {
   649  		imports, err := findImports(pkg)
   650  		if err != nil {
   651  			t.Error(err)
   652  			continue
   653  		}
   654  		if sawImport[pkg] == nil {
   655  			sawImport[pkg] = map[string]bool{}
   656  		}
   657  		var bad []string
   658  		for _, imp := range imports {
   659  			sawImport[pkg][imp] = true
   660  			if !policy.HasEdge(pkg, imp) {
   661  				bad = append(bad, imp)
   662  			}
   663  		}
   664  		if bad != nil {
   665  			t.Errorf("unexpected dependency: %s imports %v", pkg, bad)
   666  		}
   667  	}
   668  }
   669  
   670  var buildIgnore = []byte("\n//go:build ignore")
   671  
   672  func findImports(pkg string) ([]string, error) {
   673  	vpkg := pkg
   674  	if strings.HasPrefix(pkg, "golang.org") {
   675  		vpkg = "vendor/" + pkg
   676  	}
   677  	dir := filepath.Join(Default.GOROOT, "src", vpkg)
   678  	files, err := os.ReadDir(dir)
   679  	if err != nil {
   680  		return nil, err
   681  	}
   682  	var imports []string
   683  	var haveImport = map[string]bool{}
   684  	if pkg == "crypto/internal/boring" {
   685  		haveImport["C"] = true // kludge: prevent C from appearing in crypto/internal/boring imports
   686  	}
   687  	fset := token.NewFileSet()
   688  	for _, file := range files {
   689  		name := file.Name()
   690  		if name == "slice_go14.go" || name == "slice_go18.go" {
   691  			// These files are for compiler bootstrap with older versions of Go and not built in the standard build.
   692  			continue
   693  		}
   694  		if !strings.HasSuffix(name, ".go") || strings.HasSuffix(name, "_test.go") {
   695  			continue
   696  		}
   697  		info := fileInfo{
   698  			name: filepath.Join(dir, name),
   699  			fset: fset,
   700  		}
   701  		f, err := os.Open(info.name)
   702  		if err != nil {
   703  			return nil, err
   704  		}
   705  		err = readGoInfo(f, &info)
   706  		f.Close()
   707  		if err != nil {
   708  			return nil, fmt.Errorf("reading %v: %v", name, err)
   709  		}
   710  		if info.parsed.Name.Name == "main" {
   711  			continue
   712  		}
   713  		if bytes.Contains(info.header, buildIgnore) {
   714  			continue
   715  		}
   716  		for _, imp := range info.imports {
   717  			path := imp.path
   718  			if !haveImport[path] {
   719  				haveImport[path] = true
   720  				imports = append(imports, path)
   721  			}
   722  		}
   723  	}
   724  	sort.Strings(imports)
   725  	return imports, nil
   726  }
   727  
   728  // depsPolicy returns a map m such that m[p][d] == true when p can import d.
   729  func depsPolicy(t *testing.T) *dag.Graph {
   730  	g, err := dag.Parse(depsRules)
   731  	if err != nil {
   732  		t.Fatal(err)
   733  	}
   734  	return g
   735  }
   736  
   737  // TestStdlibLowercase tests that all standard library package names are
   738  // lowercase. See Issue 40065.
   739  func TestStdlibLowercase(t *testing.T) {
   740  	if !testenv.HasSrc() {
   741  		t.Skipf("skipping on %s/%s, missing full GOROOT", runtime.GOOS, runtime.GOARCH)
   742  	}
   743  
   744  	ctxt := Default
   745  	all, err := listStdPkgs(ctxt.GOROOT)
   746  	if err != nil {
   747  		t.Fatal(err)
   748  	}
   749  
   750  	for _, pkgname := range all {
   751  		if strings.ToLower(pkgname) != pkgname {
   752  			t.Errorf("package %q should not use upper-case path", pkgname)
   753  		}
   754  	}
   755  }
   756  
   757  // TestFindImports tests that findImports works.  See #43249.
   758  func TestFindImports(t *testing.T) {
   759  	imports, err := findImports("go/build")
   760  	if err != nil {
   761  		t.Fatal(err)
   762  	}
   763  	t.Logf("go/build imports %q", imports)
   764  	want := []string{"bytes", "os", "path/filepath", "strings"}
   765  wantLoop:
   766  	for _, w := range want {
   767  		for _, imp := range imports {
   768  			if imp == w {
   769  				continue wantLoop
   770  			}
   771  		}
   772  		t.Errorf("expected to find %q in import list", w)
   773  	}
   774  }
   775  

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