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
8package build
9
10import (
11	"bytes"
12	"fmt"
13	"go/token"
14	"internal/dag"
15	"internal/testenv"
16	"io/fs"
17	"os"
18	"path/filepath"
19	"runtime"
20	"slices"
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.
39var depsRules = `
40	# No dependencies allowed for any of these packages.
41	NONE
42	< unsafe
43	< cmp,
44	  container/list,
45	  container/ring,
46	  internal/byteorder,
47	  internal/cfg,
48	  internal/coverage,
49	  internal/coverage/rtcov,
50	  internal/coverage/uleb128,
51	  internal/coverage/calloc,
52	  internal/cpu,
53	  internal/goarch,
54	  internal/godebugs,
55	  internal/goexperiment,
56	  internal/goos,
57	  internal/goversion,
58	  internal/nettrace,
59	  internal/platform,
60	  internal/profilerecord,
61	  internal/trace/traceviewer/format,
62	  log/internal,
63	  math/bits,
64	  unicode,
65	  unicode/utf8,
66	  unicode/utf16;
67
68	internal/goarch < internal/abi;
69	internal/byteorder, internal/goarch < internal/chacha8rand;
70
71	# RUNTIME is the core runtime group of packages, all of them very light-weight.
72	internal/abi,
73	internal/chacha8rand,
74	internal/coverage/rtcov,
75	internal/cpu,
76	internal/goarch,
77	internal/godebugs,
78	internal/goexperiment,
79	internal/goos,
80	internal/profilerecord,
81	math/bits
82	< internal/bytealg
83	< internal/stringslite
84	< internal/itoa
85	< internal/unsafeheader
86	< runtime/internal/sys
87	< internal/runtime/syscall
88	< internal/runtime/atomic
89	< internal/runtime/exithook
90	< runtime/internal/math
91	< runtime
92	< sync/atomic
93	< internal/race
94	< internal/msan
95	< internal/asan
96	< internal/weak
97	< sync
98	< internal/bisect
99	< internal/godebug
100	< internal/reflectlite
101	< errors
102	< internal/oserror;
103
104	cmp, internal/race, math/bits
105	< iter
106	< maps, slices;
107
108	internal/oserror, maps, slices
109	< RUNTIME;
110
111	RUNTIME
112	< sort
113	< container/heap;
114
115	RUNTIME
116	< io;
117
118	RUNTIME
119	< arena;
120
121	syscall !< io;
122	reflect !< sort;
123
124	RUNTIME, unicode/utf8
125	< path;
126
127	unicode !< path;
128
129	# SYSCALL is RUNTIME plus the packages necessary for basic system calls.
130	RUNTIME, unicode/utf8, unicode/utf16
131	< internal/syscall/windows/sysdll, syscall/js
132	< syscall
133	< internal/syscall/unix, internal/syscall/windows, internal/syscall/windows/registry
134	< internal/syscall/execenv
135	< SYSCALL;
136
137	# TIME is SYSCALL plus the core packages about time, including context.
138	SYSCALL
139	< time/tzdata
140	< time
141	< context
142	< TIME;
143
144	TIME, io, path, slices
145	< io/fs;
146
147	# MATH is RUNTIME plus the basic math packages.
148	RUNTIME
149	< math
150	< MATH;
151
152	unicode !< math;
153
154	MATH
155	< math/cmplx;
156
157	MATH
158	< math/rand, math/rand/v2;
159
160	MATH
161	< runtime/metrics;
162
163	RUNTIME, math/rand/v2
164	< internal/concurrent;
165
166	MATH, unicode/utf8
167	< strconv;
168
169	unicode !< strconv;
170
171	# STR is basic string and buffer manipulation.
172	RUNTIME, io, unicode/utf8, unicode/utf16, unicode
173	< bytes, strings
174	< bufio;
175
176	bufio, path, strconv
177	< STR;
178
179	RUNTIME, internal/concurrent
180	< unique;
181
182	# OS is basic OS access, including helpers (path/filepath, os/exec, etc).
183	# OS includes string routines, but those must be layered above package os.
184	# OS does not include reflection.
185	io/fs
186	< internal/testlog
187	< internal/poll
188	< internal/filepathlite
189	< os
190	< os/signal;
191
192	io/fs
193	< embed;
194
195	unicode, fmt !< net, os, os/signal;
196
197	os/signal, internal/filepathlite, STR
198	< path/filepath
199	< io/ioutil;
200
201	path/filepath, internal/godebug < os/exec;
202
203	io/ioutil, os/exec, os/signal
204	< OS;
205
206	reflect !< OS;
207
208	OS
209	< golang.org/x/sys/cpu;
210
211	# FMT is OS (which includes string routines) plus reflect and fmt.
212	# It does not include package log, which should be avoided in core packages.
213	arena, strconv, unicode
214	< reflect;
215
216	os, reflect
217	< internal/fmtsort
218	< fmt;
219
220	OS, fmt
221	< FMT;
222
223	log !< FMT;
224
225	# Misc packages needing only FMT.
226	FMT
227	< html,
228	  internal/dag,
229	  internal/goroot,
230	  internal/types/errors,
231	  mime/quotedprintable,
232	  net/internal/socktest,
233	  net/url,
234	  runtime/trace,
235	  text/scanner,
236	  text/tabwriter;
237
238	io, reflect
239	< internal/saferio;
240
241	# encodings
242	# core ones do not use fmt.
243	io, strconv, slices
244	< encoding;
245
246	encoding, reflect
247	< encoding/binary
248	< encoding/base32, encoding/base64;
249
250	FMT, encoding < flag;
251
252	fmt !< encoding/base32, encoding/base64;
253
254	FMT, encoding/base32, encoding/base64, internal/saferio
255	< encoding/ascii85, encoding/csv, encoding/gob, encoding/hex,
256	  encoding/json, encoding/pem, encoding/xml, mime;
257
258	# hashes
259	io
260	< hash
261	< hash/adler32, hash/crc32, hash/crc64, hash/fnv;
262
263	# math/big
264	FMT, math/rand
265	< math/big;
266
267	# compression
268	FMT, encoding/binary, hash/adler32, hash/crc32, sort
269	< compress/bzip2, compress/flate, compress/lzw, internal/zstd
270	< archive/zip, compress/gzip, compress/zlib;
271
272	# templates
273	FMT
274	< text/template/parse;
275
276	net/url, text/template/parse
277	< text/template
278	< internal/lazytemplate;
279
280	# regexp
281	FMT, sort
282	< regexp/syntax
283	< regexp
284	< internal/lazyregexp;
285
286	encoding/json, html, text/template, regexp
287	< html/template;
288
289	# suffix array
290	encoding/binary, regexp
291	< index/suffixarray;
292
293	# executable parsing
294	FMT, encoding/binary, compress/zlib, internal/saferio, internal/zstd, sort
295	< runtime/debug
296	< debug/dwarf
297	< debug/elf, debug/gosym, debug/macho, debug/pe, debug/plan9obj, internal/xcoff
298	< debug/buildinfo
299	< DEBUG;
300
301	# go parser and friends.
302	FMT, sort
303	< internal/gover
304	< go/version
305	< go/token
306	< go/scanner
307	< go/ast
308	< go/internal/typeparams;
309
310	FMT
311	< go/build/constraint;
312
313	FMT, sort
314	< go/doc/comment;
315
316	go/internal/typeparams, go/build/constraint
317	< go/parser;
318
319	go/doc/comment, go/parser, text/tabwriter
320	< go/printer
321	< go/format;
322
323	math/big, go/token
324	< go/constant;
325
326	FMT, internal/goexperiment
327	< internal/buildcfg;
328
329	container/heap, go/constant, go/parser, internal/buildcfg, internal/goversion, internal/types/errors
330	< go/types;
331
332	# The vast majority of standard library packages should not be resorting to regexp.
333	# go/types is a good chokepoint. It shouldn't use regexp, nor should anything
334	# that is low-enough level to be used by go/types.
335	regexp !< go/types;
336
337	go/doc/comment, go/parser, internal/lazyregexp, text/template
338	< go/doc;
339
340	go/build/constraint, go/doc, go/parser, internal/buildcfg, internal/goroot, internal/goversion, internal/platform
341	< go/build;
342
343	# databases
344	FMT
345	< database/sql/internal
346	< database/sql/driver;
347
348	database/sql/driver, math/rand/v2 < database/sql;
349
350	# images
351	FMT, compress/lzw, compress/zlib
352	< image/color
353	< image, image/color/palette
354	< image/internal/imageutil
355	< image/draw
356	< image/gif, image/jpeg, image/png;
357
358	# cgo, delayed as long as possible.
359	# If you add a dependency on CGO, you must add the package
360	# to cgoPackages in cmd/dist/test.go as well.
361	RUNTIME
362	< C
363	< runtime/cgo
364	< CGO
365	< runtime/msan, runtime/asan;
366
367	# runtime/race
368	NONE < runtime/race/internal/amd64v1;
369	NONE < runtime/race/internal/amd64v3;
370	CGO, runtime/race/internal/amd64v1, runtime/race/internal/amd64v3 < runtime/race;
371
372	# Bulk of the standard library must not use cgo.
373	# The prohibition stops at net and os/user.
374	C !< fmt, go/types, CRYPTO-MATH, log/slog;
375
376	CGO, OS
377	< plugin;
378
379	CGO, FMT
380	< os/user
381	< archive/tar;
382
383	sync
384	< internal/singleflight;
385
386	os
387	< golang.org/x/net/dns/dnsmessage,
388	  golang.org/x/net/lif,
389	  golang.org/x/net/route;
390
391	internal/bytealg, internal/itoa, math/bits, slices, strconv, unique
392	< net/netip;
393
394	# net is unavoidable when doing any networking,
395	# so large dependencies must be kept out.
396	# This is a long-looking list but most of these
397	# are small with few dependencies.
398	CGO,
399	golang.org/x/net/dns/dnsmessage,
400	golang.org/x/net/lif,
401	golang.org/x/net/route,
402	internal/godebug,
403	internal/nettrace,
404	internal/poll,
405	internal/singleflight,
406	net/netip,
407	os,
408	sort
409	< net;
410
411	fmt, unicode !< net;
412	math/rand !< net; # net uses runtime instead
413
414	# NET is net plus net-helper packages.
415	FMT, net
416	< net/textproto;
417
418	mime, net/textproto, net/url
419	< NET;
420
421	# logging - most packages should not import; http and up is allowed
422	FMT, log/internal
423	< log;
424
425	log, log/slog !< crypto/tls, database/sql, go/importer, testing;
426
427	FMT, log, net
428	< log/syslog;
429
430	RUNTIME
431	< log/slog/internal, log/slog/internal/buffer;
432
433	FMT,
434	encoding, encoding/json,
435	log, log/internal,
436	log/slog/internal, log/slog/internal/buffer,
437	slices
438	< log/slog
439	< log/slog/internal/slogtest, log/slog/internal/benchmarks;
440
441	NET, log
442	< net/mail;
443
444	NONE < crypto/internal/boring/sig, crypto/internal/boring/syso;
445	sync/atomic < crypto/internal/boring/bcache, crypto/internal/boring/fipstls;
446	crypto/internal/boring/sig, crypto/internal/boring/fipstls < crypto/tls/fipsonly;
447
448	# CRYPTO is core crypto algorithms - no cgo, fmt, net.
449	crypto/internal/boring/sig,
450	crypto/internal/boring/syso,
451	golang.org/x/sys/cpu,
452	hash, embed
453	< crypto
454	< crypto/subtle
455	< crypto/internal/alias
456	< crypto/cipher;
457
458	crypto/cipher,
459	crypto/internal/boring/bcache
460	< crypto/internal/boring
461	< crypto/boring;
462
463	crypto/internal/alias
464	< crypto/internal/randutil
465	< crypto/internal/nistec/fiat
466	< crypto/internal/nistec
467	< crypto/internal/edwards25519/field
468	< crypto/internal/edwards25519;
469
470	crypto/boring
471	< crypto/aes, crypto/des, crypto/hmac, crypto/md5, crypto/rc4,
472	  crypto/sha1, crypto/sha256, crypto/sha512;
473
474	crypto/boring, crypto/internal/edwards25519/field
475	< crypto/ecdh;
476
477	# Unfortunately, stuck with reflect via encoding/binary.
478	encoding/binary, crypto/boring < golang.org/x/crypto/sha3;
479
480	crypto/aes,
481	crypto/des,
482	crypto/ecdh,
483	crypto/hmac,
484	crypto/internal/edwards25519,
485	crypto/md5,
486	crypto/rc4,
487	crypto/sha1,
488	crypto/sha256,
489	crypto/sha512,
490	golang.org/x/crypto/sha3
491	< CRYPTO;
492
493	CGO, fmt, net !< CRYPTO;
494
495	# CRYPTO-MATH is core bignum-based crypto - no cgo, net; fmt now ok.
496	CRYPTO, FMT, math/big
497	< crypto/internal/boring/bbig
498	< crypto/rand
499	< crypto/internal/mlkem768
500	< crypto/ed25519
501	< encoding/asn1
502	< golang.org/x/crypto/cryptobyte/asn1
503	< golang.org/x/crypto/cryptobyte
504	< crypto/internal/bigmod
505	< crypto/dsa, crypto/elliptic, crypto/rsa
506	< crypto/ecdsa
507	< CRYPTO-MATH;
508
509	CGO, net !< CRYPTO-MATH;
510
511	# TLS, Prince of Dependencies.
512	CRYPTO-MATH, NET, container/list, encoding/hex, encoding/pem
513	< golang.org/x/crypto/internal/alias
514	< golang.org/x/crypto/internal/subtle
515	< golang.org/x/crypto/chacha20
516	< golang.org/x/crypto/internal/poly1305
517	< golang.org/x/crypto/chacha20poly1305
518	< golang.org/x/crypto/hkdf
519	< crypto/internal/hpke
520	< crypto/x509/internal/macos
521	< crypto/x509/pkix;
522
523	crypto/internal/boring/fipstls, crypto/x509/pkix
524	< crypto/x509
525	< crypto/tls;
526
527	# crypto-aware packages
528
529	DEBUG, go/build, go/types, text/scanner, crypto/md5
530	< internal/pkgbits
531	< go/internal/gcimporter, go/internal/gccgoimporter, go/internal/srcimporter
532	< go/importer;
533
534	NET, crypto/rand, mime/quotedprintable
535	< mime/multipart;
536
537	crypto/tls
538	< net/smtp;
539
540	crypto/rand
541	< hash/maphash; # for purego implementation
542
543	# HTTP, King of Dependencies.
544
545	FMT
546	< golang.org/x/net/http2/hpack
547	< net/http/internal, net/http/internal/ascii, net/http/internal/testcert;
548
549	FMT, NET, container/list, encoding/binary, log
550	< golang.org/x/text/transform
551	< golang.org/x/text/unicode/norm
552	< golang.org/x/text/unicode/bidi
553	< golang.org/x/text/secure/bidirule
554	< golang.org/x/net/idna
555	< golang.org/x/net/http/httpguts, golang.org/x/net/http/httpproxy;
556
557	NET, crypto/tls
558	< net/http/httptrace;
559
560	compress/gzip,
561	golang.org/x/net/http/httpguts,
562	golang.org/x/net/http/httpproxy,
563	golang.org/x/net/http2/hpack,
564	net/http/internal,
565	net/http/internal/ascii,
566	net/http/internal/testcert,
567	net/http/httptrace,
568	mime/multipart,
569	log
570	< net/http;
571
572	# HTTP-aware packages
573
574	encoding/json, net/http
575	< expvar;
576
577	net/http, net/http/internal/ascii
578	< net/http/cookiejar, net/http/httputil;
579
580	net/http, flag
581	< net/http/httptest;
582
583	net/http, regexp
584	< net/http/cgi
585	< net/http/fcgi;
586
587	# Profiling
588	FMT, compress/gzip, encoding/binary, sort, text/tabwriter
589	< runtime/pprof;
590
591	OS, compress/gzip, internal/lazyregexp
592	< internal/profile;
593
594	html, internal/profile, net/http, runtime/pprof, runtime/trace
595	< net/http/pprof;
596
597	# RPC
598	encoding/gob, encoding/json, go/token, html/template, net/http
599	< net/rpc
600	< net/rpc/jsonrpc;
601
602	# System Information
603	bufio, bytes, internal/cpu, io, os, strings, sync
604	< internal/sysinfo;
605
606	# Test-only
607	log
608	< testing/iotest
609	< testing/fstest;
610
611	FMT, flag, math/rand
612	< testing/quick;
613
614	FMT, DEBUG, flag, runtime/trace, internal/sysinfo, math/rand
615	< testing;
616
617	log/slog, testing
618	< testing/slogtest;
619
620	FMT, crypto/sha256, encoding/json, go/ast, go/parser, go/token,
621	internal/godebug, math/rand, encoding/hex, crypto/sha256
622	< internal/fuzz;
623
624	OS, flag, testing, internal/cfg, internal/platform, internal/goroot
625	< internal/testenv;
626
627	OS, encoding/base64
628	< internal/obscuretestdata;
629
630	CGO, OS, fmt
631	< internal/testpty;
632
633	NET, testing, math/rand
634	< golang.org/x/net/nettest;
635
636	syscall
637	< os/exec/internal/fdtest;
638
639	FMT, sort
640	< internal/diff;
641
642	FMT
643	< internal/txtar;
644
645	CRYPTO-MATH, testing
646	< crypto/internal/cryptotest;
647
648	# v2 execution trace parser.
649	FMT
650	< internal/trace/event;
651
652	internal/trace/event
653	< internal/trace/event/go122;
654
655	FMT, io, internal/trace/event/go122
656	< internal/trace/version;
657
658	FMT, encoding/binary, internal/trace/version
659	< internal/trace/raw;
660
661	FMT, internal/trace/event, internal/trace/version, io, sort, encoding/binary
662	< internal/trace/internal/oldtrace;
663
664	FMT, encoding/binary, internal/trace/version, internal/trace/internal/oldtrace, container/heap, math/rand
665	< internal/trace;
666
667	regexp, internal/trace, internal/trace/raw, internal/txtar
668	< internal/trace/testtrace;
669
670	regexp, internal/txtar, internal/trace, internal/trace/raw
671	< internal/trace/internal/testgen/go122;
672
673	# cmd/trace dependencies.
674	FMT,
675	embed,
676	encoding/json,
677	html/template,
678	internal/profile,
679	internal/trace,
680	internal/trace/traceviewer/format,
681	net/http
682	< internal/trace/traceviewer;
683
684	# Coverage.
685	FMT, crypto/md5, encoding/binary, regexp, sort, text/tabwriter,
686	internal/coverage, internal/coverage/uleb128
687	< internal/coverage/cmerge,
688	  internal/coverage/pods,
689	  internal/coverage/slicereader,
690	  internal/coverage/slicewriter;
691
692	internal/coverage/slicereader, internal/coverage/slicewriter
693	< internal/coverage/stringtab
694	< internal/coverage/decodecounter, internal/coverage/decodemeta,
695	  internal/coverage/encodecounter, internal/coverage/encodemeta;
696
697	internal/coverage/cmerge
698	< internal/coverage/cformat;
699
700	internal/coverage, crypto/sha256, FMT
701	< cmd/internal/cov/covcmd;
702
703	encoding/json,
704	runtime/debug,
705	internal/coverage/calloc,
706	internal/coverage/cformat,
707	internal/coverage/decodecounter, internal/coverage/decodemeta,
708	internal/coverage/encodecounter, internal/coverage/encodemeta,
709	internal/coverage/pods
710	< internal/coverage/cfile
711	< runtime/coverage;
712
713	internal/coverage/cfile, internal/fuzz, internal/testlog, runtime/pprof, regexp
714	< testing/internal/testdeps;
715
716	# Test-only packages can have anything they want
717	CGO, internal/syscall/unix < net/internal/cgotest;
718
719
720`
721
722// listStdPkgs returns the same list of packages as "go list std".
723func listStdPkgs(goroot string) ([]string, error) {
724	// Based on cmd/go's matchPackages function.
725	var pkgs []string
726
727	src := filepath.Join(goroot, "src") + string(filepath.Separator)
728	walkFn := func(path string, d fs.DirEntry, err error) error {
729		if err != nil || !d.IsDir() || path == src {
730			return nil
731		}
732
733		base := filepath.Base(path)
734		if strings.HasPrefix(base, ".") || strings.HasPrefix(base, "_") || base == "testdata" {
735			return filepath.SkipDir
736		}
737
738		name := filepath.ToSlash(path[len(src):])
739		if name == "builtin" || name == "cmd" {
740			return filepath.SkipDir
741		}
742
743		pkgs = append(pkgs, strings.TrimPrefix(name, "vendor/"))
744		return nil
745	}
746	if err := filepath.WalkDir(src, walkFn); err != nil {
747		return nil, err
748	}
749	return pkgs, nil
750}
751
752func TestDependencies(t *testing.T) {
753	if !testenv.HasSrc() {
754		// Tests run in a limited file system and we do not
755		// provide access to every source file.
756		t.Skipf("skipping on %s/%s, missing full GOROOT", runtime.GOOS, runtime.GOARCH)
757	}
758
759	ctxt := Default
760	all, err := listStdPkgs(ctxt.GOROOT)
761	if err != nil {
762		t.Fatal(err)
763	}
764	slices.Sort(all)
765
766	sawImport := map[string]map[string]bool{} // from package => to package => true
767	policy := depsPolicy(t)
768
769	for _, pkg := range all {
770		imports, err := findImports(pkg)
771		if err != nil {
772			t.Error(err)
773			continue
774		}
775		if sawImport[pkg] == nil {
776			sawImport[pkg] = map[string]bool{}
777		}
778		var bad []string
779		for _, imp := range imports {
780			sawImport[pkg][imp] = true
781			if !policy.HasEdge(pkg, imp) {
782				bad = append(bad, imp)
783			}
784		}
785		if bad != nil {
786			t.Errorf("unexpected dependency: %s imports %v", pkg, bad)
787		}
788	}
789}
790
791var buildIgnore = []byte("\n//go:build ignore")
792
793func findImports(pkg string) ([]string, error) {
794	vpkg := pkg
795	if strings.HasPrefix(pkg, "golang.org") {
796		vpkg = "vendor/" + pkg
797	}
798	dir := filepath.Join(Default.GOROOT, "src", vpkg)
799	files, err := os.ReadDir(dir)
800	if err != nil {
801		return nil, err
802	}
803	var imports []string
804	var haveImport = map[string]bool{}
805	if pkg == "crypto/internal/boring" {
806		haveImport["C"] = true // kludge: prevent C from appearing in crypto/internal/boring imports
807	}
808	fset := token.NewFileSet()
809	for _, file := range files {
810		name := file.Name()
811		if name == "slice_go14.go" || name == "slice_go18.go" {
812			// These files are for compiler bootstrap with older versions of Go and not built in the standard build.
813			continue
814		}
815		if !strings.HasSuffix(name, ".go") || strings.HasSuffix(name, "_test.go") {
816			continue
817		}
818		info := fileInfo{
819			name: filepath.Join(dir, name),
820			fset: fset,
821		}
822		f, err := os.Open(info.name)
823		if err != nil {
824			return nil, err
825		}
826		err = readGoInfo(f, &info)
827		f.Close()
828		if err != nil {
829			return nil, fmt.Errorf("reading %v: %v", name, err)
830		}
831		if info.parsed.Name.Name == "main" {
832			continue
833		}
834		if bytes.Contains(info.header, buildIgnore) {
835			continue
836		}
837		for _, imp := range info.imports {
838			path := imp.path
839			if !haveImport[path] {
840				haveImport[path] = true
841				imports = append(imports, path)
842			}
843		}
844	}
845	slices.Sort(imports)
846	return imports, nil
847}
848
849// depsPolicy returns a map m such that m[p][d] == true when p can import d.
850func depsPolicy(t *testing.T) *dag.Graph {
851	g, err := dag.Parse(depsRules)
852	if err != nil {
853		t.Fatal(err)
854	}
855	return g
856}
857
858// TestStdlibLowercase tests that all standard library package names are
859// lowercase. See Issue 40065.
860func TestStdlibLowercase(t *testing.T) {
861	if !testenv.HasSrc() {
862		t.Skipf("skipping on %s/%s, missing full GOROOT", runtime.GOOS, runtime.GOARCH)
863	}
864
865	ctxt := Default
866	all, err := listStdPkgs(ctxt.GOROOT)
867	if err != nil {
868		t.Fatal(err)
869	}
870
871	for _, pkgname := range all {
872		if strings.ToLower(pkgname) != pkgname {
873			t.Errorf("package %q should not use upper-case path", pkgname)
874		}
875	}
876}
877
878// TestFindImports tests that findImports works.  See #43249.
879func TestFindImports(t *testing.T) {
880	imports, err := findImports("go/build")
881	if err != nil {
882		t.Fatal(err)
883	}
884	t.Logf("go/build imports %q", imports)
885	want := []string{"bytes", "os", "path/filepath", "strings"}
886wantLoop:
887	for _, w := range want {
888		for _, imp := range imports {
889			if imp == w {
890				continue wantLoop
891			}
892		}
893		t.Errorf("expected to find %q in import list", w)
894	}
895}
896