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// Copyright 2020 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package modload
import (
"context"
"errors"
"fmt"
"os"
"path/filepath"
"sort"
"cmd/go/internal/modfetch"
"cmd/go/internal/mvs"
"golang.org/x/mod/module"
"golang.org/x/mod/semver"
)
// mvsReqs implements mvs.Reqs for module semantic versions,
// with any exclusions or replacements applied internally.
type mvsReqs struct {
buildList []module.Version
}
// Reqs returns the current module requirement graph.
// Future calls to SetBuildList do not affect the operation
// of the returned Reqs.
func Reqs() mvs.Reqs {
r := &mvsReqs{
buildList: buildList,
}
return r
}
func (r *mvsReqs) Required(mod module.Version) ([]module.Version, error) {
if mod == Target {
// Use the build list as it existed when r was constructed, not the current
// global build list.
return r.buildList[1:], nil
}
if mod.Version == "none" {
return nil, nil
}
summary, err := goModSummary(mod)
if err != nil {
return nil, err
}
return summary.require, nil
}
// Max returns the maximum of v1 and v2 according to semver.Compare.
//
// As a special case, the version "" is considered higher than all other
// versions. The main module (also known as the target) has no version and must
// be chosen over other versions of the same module in the module dependency
// graph.
func (*mvsReqs) Max(v1, v2 string) string {
if v1 != "" && semver.Compare(v1, v2) == -1 {
return v2
}
return v1
}
// Upgrade is a no-op, here to implement mvs.Reqs.
// The upgrade logic for go get -u is in ../modget/get.go.
func (*mvsReqs) Upgrade(m module.Version) (module.Version, error) {
return m, nil
}
func versions(ctx context.Context, path string, allowed AllowedFunc) ([]string, error) {
// Note: modfetch.Lookup and repo.Versions are cached,
// so there's no need for us to add extra caching here.
var versions []string
err := modfetch.TryProxies(func(proxy string) error {
repo, err := modfetch.Lookup(proxy, path)
if err != nil {
return err
}
allVersions, err := repo.Versions("")
if err != nil {
return err
}
allowedVersions := make([]string, 0, len(allVersions))
for _, v := range allVersions {
if err := allowed(ctx, module.Version{Path: path, Version: v}); err == nil {
allowedVersions = append(allowedVersions, v)
} else if !errors.Is(err, ErrDisallowed) {
return err
}
}
versions = allowedVersions
return nil
})
return versions, err
}
// Previous returns the tagged version of m.Path immediately prior to
// m.Version, or version "none" if no prior version is tagged.
func (*mvsReqs) Previous(m module.Version) (module.Version, error) {
// TODO(golang.org/issue/38714): thread tracing context through MVS.
list, err := versions(context.TODO(), m.Path, CheckAllowed)
if err != nil {
return module.Version{}, err
}
i := sort.Search(len(list), func(i int) bool { return semver.Compare(list[i], m.Version) >= 0 })
if i > 0 {
return module.Version{Path: m.Path, Version: list[i-1]}, nil
}
return module.Version{Path: m.Path, Version: "none"}, nil
}
// next returns the next version of m.Path after m.Version.
// It is only used by the exclusion processing in the Required method,
// not called directly by MVS.
func (*mvsReqs) next(m module.Version) (module.Version, error) {
// TODO(golang.org/issue/38714): thread tracing context through MVS.
list, err := versions(context.TODO(), m.Path, CheckAllowed)
if err != nil {
return module.Version{}, err
}
i := sort.Search(len(list), func(i int) bool { return semver.Compare(list[i], m.Version) > 0 })
if i < len(list) {
return module.Version{Path: m.Path, Version: list[i]}, nil
}
return module.Version{Path: m.Path, Version: "none"}, nil
}
// fetch downloads the given module (or its replacement)
// and returns its location.
//
// The isLocal return value reports whether the replacement,
// if any, is local to the filesystem.
func fetch(ctx context.Context, mod module.Version) (dir string, isLocal bool, err error) {
if mod == Target {
return ModRoot(), true, nil
}
if r := Replacement(mod); r.Path != "" {
if r.Version == "" {
dir = r.Path
if !filepath.IsAbs(dir) {
dir = filepath.Join(ModRoot(), dir)
}
// Ensure that the replacement directory actually exists:
// dirInModule does not report errors for missing modules,
// so if we don't report the error now, later failures will be
// very mysterious.
if _, err := os.Stat(dir); err != nil {
if os.IsNotExist(err) {
// Semantically the module version itself “exists” — we just don't
// have its source code. Remove the equivalence to os.ErrNotExist,
// and make the message more concise while we're at it.
err = fmt.Errorf("replacement directory %s does not exist", r.Path)
} else {
err = fmt.Errorf("replacement directory %s: %w", r.Path, err)
}
return dir, true, module.VersionError(mod, err)
}
return dir, true, nil
}
mod = r
}
dir, err = modfetch.Download(ctx, mod)
return dir, false, err
}
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