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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 source
import (
"context"
"fmt"
"go/parser"
"go/token"
"sort"
"strings"
"sync"
"time"
"golang.org/x/tools/internal/event"
"golang.org/x/tools/internal/imports"
)
// KnownPackagePaths returns a new list of package paths of all known
// packages in the package graph that could potentially be imported by
// the given file. The list is ordered lexicographically, except that
// all dot-free paths (standard packages) appear before dotful ones.
//
// It is part of the gopls.list_known_packages command.
func KnownPackagePaths(ctx context.Context, snapshot Snapshot, fh VersionedFileHandle) ([]PackagePath, error) {
// This algorithm is expressed in terms of Metadata, not Packages,
// so it doesn't cause or wait for type checking.
// Find a Metadata containing the file.
metas, err := snapshot.MetadataForFile(ctx, fh.URI())
if err != nil {
return nil, err // e.g. context cancelled
}
if len(metas) == 0 {
return nil, fmt.Errorf("no loaded package contain file %s", fh.URI())
}
current := metas[0] // pick one arbitrarily (they should all have the same package path)
// Parse the file's imports so we can compute which
// PackagePaths are imported by this specific file.
src, err := fh.Read()
if err != nil {
return nil, err
}
file, err := parser.ParseFile(token.NewFileSet(), fh.URI().Filename(), src, parser.ImportsOnly)
if err != nil {
return nil, err
}
imported := make(map[PackagePath]bool)
for _, imp := range file.Imports {
if id := current.DepsByImpPath[UnquoteImportPath(imp)]; id != "" {
if m := snapshot.Metadata(id); m != nil {
imported[m.PkgPath] = true
}
}
}
// Now find candidates among known packages.
knownPkgs, err := snapshot.AllMetadata(ctx)
if err != nil {
return nil, err
}
seen := make(map[PackagePath]bool)
for _, knownPkg := range knownPkgs {
// package main cannot be imported
if knownPkg.Name == "main" {
continue
}
// test packages cannot be imported
if knownPkg.ForTest != "" {
continue
}
// No need to import what the file already imports.
// This check is based on PackagePath, not PackageID,
// so that all test variants are filtered out too.
if imported[knownPkg.PkgPath] {
continue
}
// make sure internal packages are importable by the file
if !IsValidImport(current.PkgPath, knownPkg.PkgPath) {
continue
}
// naive check on cyclical imports
if isDirectlyCyclical(current, knownPkg) {
continue
}
// AllMetadata may have multiple variants of a pkg.
seen[knownPkg.PkgPath] = true
}
// Augment the set by invoking the goimports algorithm.
if err := snapshot.RunProcessEnvFunc(ctx, func(o *imports.Options) error {
ctx, cancel := context.WithTimeout(ctx, time.Millisecond*80)
defer cancel()
var seenMu sync.Mutex
wrapped := func(ifix imports.ImportFix) {
seenMu.Lock()
defer seenMu.Unlock()
// TODO(adonovan): what if the actual package path has a vendor/ prefix?
seen[PackagePath(ifix.StmtInfo.ImportPath)] = true
}
return imports.GetAllCandidates(ctx, wrapped, "", fh.URI().Filename(), string(current.Name), o.Env)
}); err != nil {
// If goimports failed, proceed with just the candidates from the metadata.
event.Error(ctx, "imports.GetAllCandidates", err)
}
// Sort lexicographically, but with std before non-std packages.
paths := make([]PackagePath, 0, len(seen))
for path := range seen {
paths = append(paths, path)
}
sort.Slice(paths, func(i, j int) bool {
importI, importJ := paths[i], paths[j]
iHasDot := strings.Contains(string(importI), ".")
jHasDot := strings.Contains(string(importJ), ".")
if iHasDot != jHasDot {
return jHasDot // dot-free paths (standard packages) compare less
}
return importI < importJ
})
return paths, nil
}
// isDirectlyCyclical checks if imported directly imports pkg.
// It does not (yet) offer a full cyclical check because showing a user
// a list of importable packages already generates a very large list
// and having a few false positives in there could be worth the
// performance snappiness.
//
// TODO(adonovan): ensure that metadata graph is always cyclic!
// Many algorithms will get confused or even stuck in the
// presence of cycles. Then replace this function by 'false'.
func isDirectlyCyclical(pkg, imported *Metadata) bool {
_, ok := imported.DepsByPkgPath[pkg.PkgPath]
return ok
}
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