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// Copyright 2022 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 work
import (
"context"
"errors"
"fmt"
"os"
"path/filepath"
"sort"
"strings"
"golang.org/x/tools/gopls/internal/lsp/protocol"
"golang.org/x/tools/gopls/internal/lsp/source"
"golang.org/x/tools/internal/event"
)
func Completion(ctx context.Context, snapshot source.Snapshot, fh source.FileHandle, position protocol.Position) (*protocol.CompletionList, error) {
ctx, done := event.Start(ctx, "work.Completion")
defer done()
// Get the position of the cursor.
pw, err := snapshot.ParseWork(ctx, fh)
if err != nil {
return nil, fmt.Errorf("getting go.work file handle: %w", err)
}
cursor, err := pw.Mapper.PositionOffset(position)
if err != nil {
return nil, fmt.Errorf("computing cursor offset: %w", err)
}
// Find the use statement the user is in.
use, pathStart, _ := usePath(pw, cursor)
if use == nil {
return &protocol.CompletionList{}, nil
}
completingFrom := use.Path[:cursor-pathStart]
// We're going to find the completions of the user input
// (completingFrom) by doing a walk on the innermost directory
// of the given path, and comparing the found paths to make sure
// that they match the component of the path after the
// innermost directory.
//
// We'll maintain two paths when doing this: pathPrefixSlash
// is essentially the path the user typed in, and pathPrefixAbs
// is the path made absolute from the go.work directory.
pathPrefixSlash := completingFrom
pathPrefixAbs := filepath.FromSlash(pathPrefixSlash)
if !filepath.IsAbs(pathPrefixAbs) {
pathPrefixAbs = filepath.Join(filepath.Dir(pw.URI.Filename()), pathPrefixAbs)
}
// pathPrefixDir is the directory that will be walked to find matches.
// If pathPrefixSlash is not explicitly a directory boundary (is either equivalent to "." or
// ends in a separator) we need to examine its parent directory to find sibling files that
// match.
depthBound := 5
pathPrefixDir, pathPrefixBase := pathPrefixAbs, ""
pathPrefixSlashDir := pathPrefixSlash
if filepath.Clean(pathPrefixSlash) != "." && !strings.HasSuffix(pathPrefixSlash, "/") {
depthBound++
pathPrefixDir, pathPrefixBase = filepath.Split(pathPrefixAbs)
pathPrefixSlashDir = dirNonClean(pathPrefixSlash)
}
var completions []string
// Stop traversing deeper once we've hit 10k files to try to stay generally under 100ms.
const numSeenBound = 10000
var numSeen int
stopWalking := errors.New("hit numSeenBound")
err = filepath.Walk(pathPrefixDir, func(wpath string, info os.FileInfo, err error) error {
if numSeen > numSeenBound {
// Stop traversing if we hit bound.
return stopWalking
}
numSeen++
// rel is the path relative to pathPrefixDir.
// Make sure that it has pathPrefixBase as a prefix
// otherwise it won't match the beginning of the
// base component of the path the user typed in.
rel := strings.TrimPrefix(wpath[len(pathPrefixDir):], string(filepath.Separator))
if info.IsDir() && wpath != pathPrefixDir && !strings.HasPrefix(rel, pathPrefixBase) {
return filepath.SkipDir
}
// Check for a match (a module directory).
if filepath.Base(rel) == "go.mod" {
relDir := strings.TrimSuffix(dirNonClean(rel), string(os.PathSeparator))
completionPath := join(pathPrefixSlashDir, filepath.ToSlash(relDir))
if !strings.HasPrefix(completionPath, completingFrom) {
return nil
}
if strings.HasSuffix(completionPath, "/") {
// Don't suggest paths that end in "/". This happens
// when the input is a path that ends in "/" and
// the completion is empty.
return nil
}
completion := completionPath[len(completingFrom):]
if completingFrom == "" && !strings.HasPrefix(completion, "./") {
// Bias towards "./" prefixes.
completion = join(".", completion)
}
completions = append(completions, completion)
}
if depth := strings.Count(rel, string(filepath.Separator)); depth >= depthBound {
return filepath.SkipDir
}
return nil
})
if err != nil && !errors.Is(err, stopWalking) {
return nil, fmt.Errorf("walking to find completions: %w", err)
}
sort.Strings(completions)
var items []protocol.CompletionItem
for _, c := range completions {
items = append(items, protocol.CompletionItem{
Label: c,
InsertText: c,
})
}
return &protocol.CompletionList{Items: items}, nil
}
// dirNonClean is filepath.Dir, without the Clean at the end.
func dirNonClean(path string) string {
vol := filepath.VolumeName(path)
i := len(path) - 1
for i >= len(vol) && !os.IsPathSeparator(path[i]) {
i--
}
return path[len(vol) : i+1]
}
func join(a, b string) string {
if a == "" {
return b
}
if b == "" {
return a
}
return strings.TrimSuffix(a, "/") + "/" + b
}
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