// will always include at least one package.
func (opts *goTest) packages() []string {
	pkgs := opts.pkgs
	if opts.pkg != "" {
		pkgs = append(pkgs[:len(pkgs):len(pkgs)], opts.pkg)
	}
	if len(pkgs) == 0 {
		panic("no packages")
	}
	return pkgs
}

// printSkip prints a skip message for all of goTest.
func (opts *goTest) printSkip(t *tester, msg string) {
	if t.json {

// As a side effect, buildStacks also constructs ld.pkgs,
// the list of all packages loaded.
func (ld *loader) buildStacks() {
	if len(ld.pkgs) > 0 {
		panic("buildStacks")
	}
	for _, pkg := range ld.roots {
		pkg.stack = pkg // sentinel to avoid processing in next loop
		ld.pkgs = append(ld.pkgs, pkg)
	}
	for i := 0; i < len(ld.pkgs); i++ { // not range: appending to ld.pkgs in loop
		pkg := ld.pkgs[i]

		pkgs := goDirPackages(t.T, longdir, singlefilepkgs)
		errPkg := len(pkgs) - 1
		if wantError && action == "errorcheckandrundir" {
			// The last pkg should compiled successfully and will be run in next case.
			// Preceding pkg must return an error from compileInDir.
			errPkg--
		}
		importcfgfile := importcfg(pkgs)
		for i, pkg := range pkgs {

	pkgOpts := load.PackageOpts{ModResolveTests: true}
	pkgs = load.PackagesAndErrors(ctx, pkgOpts, pkgArgs)
	load.CheckPackageErrors(pkgs)
	if len(pkgs) == 0 {
		base.Fatalf("no packages to test")
	}

	if testFuzz != "" {
		if !platform.FuzzSupported(cfg.Goos, cfg.Goarch) {
			base.Fatalf("-fuzz flag is not supported on %s/%s", cfg.Goos, cfg.Goarch)
		}
		if len(pkgs) != 1 {

// both retain the same versions of all packages in pkgs and satisfy the
// graph-pruning invariants (if applicable).
func tidyRoots(ctx context.Context, rs *Requirements, pkgs []*loadPkg) (*Requirements, error) {
	mainModule := MainModules.mustGetSingleMainModule()
	if rs.pruning == unpruned {
		return tidyUnprunedRoots(ctx, mainModule, rs, pkgs)
	}
	return tidyPrunedRoots(ctx, mainModule, rs, pkgs)
}

	return r.matchInModuleCache.Do(matchInModuleKey{pattern, m}, func() ([]string, error) {
		match := modload.MatchInModule(ctx, pattern, m, imports.AnyTags())
		if len(match.Errs) > 0 {
			return match.Pkgs, match.Errs[0]
		}
		return match.Pkgs, nil
	})
}

// queryNone adds a candidate set to q for each module matching q.pattern.
// Each candidate set has only one possible module version: the matched
// module at version "none".

	// Copy the runtime packages into a temporary GOROOT
	// so that we can change files.
	var dirs []string
	tg.run("list", "-deps", "runtime")
	pkgs := strings.Split(strings.TrimSpace(tg.getStdout()), "\n")
	for _, pkg := range pkgs {
		dirs = append(dirs, filepath.Join("src", pkg))
	}
	dirs = append(dirs,
		filepath.Join("pkg/tool", goHostOS+"_"+goHostArch),
		"pkg/include",
	)

	if l.flags&FlagCheckLinkname == 0 {
		return
	}

	error := func() {
		log.Fatalf("%s: invalid reference to %s", pkg, name)
	}
	pkgs, ok := blockedLinknames[name]
	if ok {
		for _, p := range pkgs {
			if pkg == p {
				return // pkg is allowed
			}
		}
		error()
	}
	r, li := l.toLocal(s)
	if r == l.extReader { // referencing external symbol is okay

		if gover.Compare(ld.requirements.GoVersion(), gover.TidyGoModSumVersion) < 0 && (ld.Tidy || cfg.BuildMod != "mod") {
			keepPkgGoModSums = false
			keepModSumsForZipSums = false
		}
		for _, pkg := range ld.pkgs {
			// We check pkg.mod.Path here instead of pkg.inStd because the
			// pseudo-package "C" is not in std, but not provided by any module (and
			// shouldn't force loading the whole module graph).