case goVersion != "":
			fmt.Fprintf(w, "## go %s\n", goVersion)
		}

		pkgs := modpkgs[m]
		sort.Strings(pkgs)
		for _, pkg := range pkgs {
			fmt.Fprintf(w, "%s\n", pkg)
			vendorPkg(vdir, pkg)
		}
	}

	if includeAllReplacements {
		// Record unused and wildcard replacements at the end of the modules.txt file:
		// without access to the complete build list, the consumer of the vendor

				if d > 0 && d < bestDepth {
					best = path
					bestDepth = d
				}
			}
			why := modload.Why(best)
			if why == "" {
				vendoring := ""
				if *whyVendor {
					vendoring = " to vendor"
				}
				why = "(main module does not need" + vendoring + " module " + m.Path + ")\n"
			}
			fmt.Printf("%s# %s\n%s", sep, m.Path, why)
			sep = "\n"
		}
	} else {
		// Resolve to packages.

-- modules.txt.required_but_not_explicit --
## workspace
# example.com/p v1.0.0 => ./p
## go 1.21
# example.com/q v1.0.0 => ./q
## explicit; go 1.21
-- required_but_not_explicit_error.txt --
go: inconsistent vendoring in $GOPATH${/}src:
	example.com/p@v1.0.0: is explicitly required in go.mod, but not marked as explicit in vendor/modules.txt

	To ignore the vendor directory, use -mod=readonly or -mod=mod.
	To sync the vendor directory, run:

cp go.mod go.mod.orig

# For modules whose go.mod file does not include a 'go' directive,
# we assume the language and dependency semantics of Go 1.16,
# but do not trigger “automatic vendoring” mode (-mod=vendor),
# which was added in Go 1.14 and was not triggered
# under the same conditions in Go 1.16 (which would instead
# default to -mod=readonly when no 'go' directive is present).

# For Go 1.16 modules, 'all' should prune out dependencies of tests,

go get
grep 'rsc.io/quote' go.mod

# Tidying the module should preserve those dependencies.
go mod tidy
grep 'rsc.io/quote' go.mod

[short] stop

# Vendoring the module's dependencies should work too.
go mod vendor
exists vendor/rsc.io/quote

# The same should work in directories with names starting with underscores.
cd $WORK/_ignored
go mod init testdata.tld/foo

env GO111MODULE=on

# Replacement should not use a vendor directory as the target.
! go mod vendor
stderr 'replacement path ./vendor/not-rsc.io/quote/v3 inside vendor directory'

cp go.mod1 go.mod
rm -r vendor

# Before vendoring, we expect to see the original directory.
go list -f '{{with .Module}}{{.Version}}{{end}} {{.Dir}}' rsc.io/quote/v3
stdout 'v3.0.0'
stdout '.*[/\\]not-rsc.io[/\\]quote[/\\]v3'

# In GOPATH mode, module legacy support does path rewriting very similar to vendoring.

env GO111MODULE=off

go list -f '{{range .Imports}}{{.}}{{"\n"}}{{end}}' old/p1
stdout ^new/p1$

go list -f '{{range .Imports}}{{.}}{{"\n"}}{{end}}' new/p1
stdout ^new/p2$           # not new/v2/p2
! stdout ^new/v2
stdout ^new/sub/x/v1/y$   # not new/sub/v2/x/v1/y
! stdout ^new/sub/v2
stdout ^new/sub/inner/x # not new/sub/v2/inner/x

go build old/p1 new/p1

# A 'go 1.13' vendor/modules.txt file is not usually sufficient
# to pass those checks.
go mod edit -go=1.14

! go list -f {{.Dir}} -tags tools all
stderr '^go: inconsistent vendoring in '$WORK[/\\]auto':$'
stderr '^\texample.com/printversion@v1.0.0: is explicitly required in go.mod, but not marked as explicit in vendor/modules.txt'

type gcimports struct {
	packages map[string]*types2.Package
	lookup   func(path string) (io.ReadCloser, error)
}

func (m *gcimports) Import(path string) (*types2.Package, error) {
	return m.ImportFrom(path, "" /* no vendoring */, 0)
}

func (m *gcimports) ImportFrom(path, srcDir string, mode types2.ImportMode) (*types2.Package, error) {
	if mode != 0 {
		panic("mode must be 0")
	}

type gcimports struct {
	fset     *token.FileSet
	packages map[string]*types.Package
	lookup   Lookup
}

func (m *gcimports) Import(path string) (*types.Package, error) {
	return m.ImportFrom(path, "" /* no vendoring */, 0)
}

func (m *gcimports) ImportFrom(path, srcDir string, mode types.ImportMode) (*types.Package, error) {
	if mode != 0 {
		panic("mode must be 0")
	}