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// Copyright 2018 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 (
"bytes"
"errors"
"fmt"
"go/build"
"internal/goroot"
"os"
"path/filepath"
"strings"
"cmd/go/internal/cfg"
"cmd/go/internal/modfetch/codehost"
"cmd/go/internal/module"
"cmd/go/internal/par"
"cmd/go/internal/search"
)
type ImportMissingError struct {
ImportPath string
Module module.Version
}
func (e *ImportMissingError) Error() string {
if e.Module.Path == "" {
return "cannot find module providing package " + e.ImportPath
}
return "missing module for import: " + e.Module.Path + "@" + e.Module.Version + " provides " + e.ImportPath
}
// Import finds the module and directory in the build list
// containing the package with the given import path.
// The answer must be unique: Import returns an error
// if multiple modules attempt to provide the same package.
// Import can return a module with an empty m.Path, for packages in the standard library.
// Import can return an empty directory string, for fake packages like "C" and "unsafe".
//
// If the package cannot be found in the current build list,
// Import returns an ImportMissingError as the error.
// If Import can identify a module that could be added to supply the package,
// the ImportMissingError records that module.
func Import(path string) (m module.Version, dir string, err error) {
if strings.Contains(path, "@") {
return module.Version{}, "", fmt.Errorf("import path should not have @version")
}
if build.IsLocalImport(path) {
return module.Version{}, "", fmt.Errorf("relative import not supported")
}
if path == "C" || path == "unsafe" {
// There's no directory for import "C" or import "unsafe".
return module.Version{}, "", nil
}
// Is the package in the standard library?
if search.IsStandardImportPath(path) {
if strings.HasPrefix(path, "golang_org/") {
return module.Version{}, filepath.Join(cfg.GOROOT, "src/vendor", path), nil
}
if goroot.IsStandardPackage(cfg.GOROOT, cfg.BuildContext.Compiler, path) {
dir := filepath.Join(cfg.GOROOT, "src", path)
return module.Version{}, dir, nil
}
}
// -mod=vendor is special.
// Everything must be in the main module or the main module's vendor directory.
if cfg.BuildMod == "vendor" {
mainDir, mainOK := dirInModule(path, Target.Path, ModRoot, true)
vendorDir, vendorOK := dirInModule(path, "", filepath.Join(ModRoot, "vendor"), false)
if mainOK && vendorOK {
return module.Version{}, "", fmt.Errorf("ambiguous import: found %s in multiple directories:\n\t%s\n\t%s", path, mainDir, vendorDir)
}
// Prefer to return main directory if there is one,
// Note that we're not checking that the package exists.
// We'll leave that for load.
if !vendorOK && mainDir != "" {
return Target, mainDir, nil
}
readVendorList()
return vendorMap[path], vendorDir, nil
}
// Check each module on the build list.
var dirs []string
var mods []module.Version
for _, m := range buildList {
if !maybeInModule(path, m.Path) {
// Avoid possibly downloading irrelevant modules.
continue
}
root, isLocal, err := fetch(m)
if err != nil {
// Report fetch error.
// Note that we don't know for sure this module is necessary,
// but it certainly _could_ provide the package, and even if we
// continue the loop and find the package in some other module,
// we need to look at this module to make sure the import is
// not ambiguous.
return module.Version{}, "", err
}
dir, ok := dirInModule(path, m.Path, root, isLocal)
if ok {
mods = append(mods, m)
dirs = append(dirs, dir)
}
}
if len(mods) == 1 {
return mods[0], dirs[0], nil
}
if len(mods) > 0 {
var buf bytes.Buffer
fmt.Fprintf(&buf, "ambiguous import: found %s in multiple modules:", path)
for i, m := range mods {
fmt.Fprintf(&buf, "\n\t%s", m.Path)
if m.Version != "" {
fmt.Fprintf(&buf, " %s", m.Version)
}
fmt.Fprintf(&buf, " (%s)", dirs[i])
}
return module.Version{}, "", errors.New(buf.String())
}
// Not on build list.
// Look up module containing the package, for addition to the build list.
// Goal is to determine the module, download it to dir, and return m, dir, ErrMissing.
if cfg.BuildMod == "readonly" {
return module.Version{}, "", fmt.Errorf("import lookup disabled by -mod=%s", cfg.BuildMod)
}
m, _, err = QueryPackage(path, "latest", Allowed)
if err != nil {
if _, ok := err.(*codehost.VCSError); ok {
return module.Version{}, "", err
}
return module.Version{}, "", &ImportMissingError{ImportPath: path}
}
return m, "", &ImportMissingError{ImportPath: path, Module: m}
}
// maybeInModule reports whether, syntactically,
// a package with the given import path could be supplied
// by a module with the given module path (mpath).
func maybeInModule(path, mpath string) bool {
return mpath == path ||
len(path) > len(mpath) && path[len(mpath)] == '/' && path[:len(mpath)] == mpath
}
var haveGoModCache, haveGoFilesCache par.Cache
// dirInModule locates the directory that would hold the package named by the given path,
// if it were in the module with module path mpath and root mdir.
// If path is syntactically not within mpath,
// or if mdir is a local file tree (isLocal == true) and the directory
// that would hold path is in a sub-module (covered by a go.mod below mdir),
// dirInModule returns "", false.
//
// Otherwise, dirInModule returns the name of the directory where
// Go source files would be expected, along with a boolean indicating
// whether there are in fact Go source files in that directory.
func dirInModule(path, mpath, mdir string, isLocal bool) (dir string, haveGoFiles bool) {
// Determine where to expect the package.
if path == mpath {
dir = mdir
} else if mpath == "" { // vendor directory
dir = filepath.Join(mdir, path)
} else if len(path) > len(mpath) && path[len(mpath)] == '/' && path[:len(mpath)] == mpath {
dir = filepath.Join(mdir, path[len(mpath)+1:])
} else {
return "", false
}
// Check that there aren't other modules in the way.
// This check is unnecessary inside the module cache
// and important to skip in the vendor directory,
// where all the module trees have been overlaid.
// So we only check local module trees
// (the main module, and any directory trees pointed at by replace directives).
if isLocal {
for d := dir; d != mdir && len(d) > len(mdir); {
haveGoMod := haveGoModCache.Do(d, func() interface{} {
_, err := os.Stat(filepath.Join(d, "go.mod"))
return err == nil
}).(bool)
if haveGoMod {
return "", false
}
parent := filepath.Dir(d)
if parent == d {
// Break the loop, as otherwise we'd loop
// forever if d=="." and mdir=="".
break
}
d = parent
}
}
// Now committed to returning dir (not "").
// Are there Go source files in the directory?
// We don't care about build tags, not even "+build ignore".
// We're just looking for a plausible directory.
haveGoFiles = haveGoFilesCache.Do(dir, func() interface{} {
f, err := os.Open(dir)
if err != nil {
return false
}
defer f.Close()
names, _ := f.Readdirnames(-1)
for _, name := range names {
if strings.HasSuffix(name, ".go") {
info, err := os.Stat(filepath.Join(dir, name))
if err == nil && info.Mode().IsRegular() {
return true
}
}
}
return false
}).(bool)
return dir, haveGoFiles
}
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