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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 completion
import (
"context"
"fmt"
"go/ast"
"go/parser"
"go/scanner"
"go/token"
"go/types"
"path/filepath"
"strings"
"golang.org/x/tools/internal/lsp/fuzzy"
"golang.org/x/tools/internal/lsp/protocol"
"golang.org/x/tools/internal/lsp/source"
"golang.org/x/tools/internal/span"
errors "golang.org/x/xerrors"
)
// packageClauseCompletions offers completions for a package declaration when
// one is not present in the given file.
func packageClauseCompletions(ctx context.Context, snapshot source.Snapshot, fh source.FileHandle, pos protocol.Position) ([]CompletionItem, *Selection, error) {
// We know that the AST for this file will be empty due to the missing
// package declaration, but parse it anyway to get a mapper.
pgf, err := snapshot.ParseGo(ctx, fh, source.ParseFull)
if err != nil {
return nil, nil, err
}
cursorSpan, err := pgf.Mapper.PointSpan(pos)
if err != nil {
return nil, nil, err
}
rng, err := cursorSpan.Range(pgf.Mapper.Converter)
if err != nil {
return nil, nil, err
}
surrounding, err := packageCompletionSurrounding(snapshot.FileSet(), fh, pgf, rng.Start)
if err != nil {
return nil, nil, errors.Errorf("invalid position for package completion: %w", err)
}
packageSuggestions, err := packageSuggestions(ctx, snapshot, fh.URI(), "")
if err != nil {
return nil, nil, err
}
var items []CompletionItem
for _, pkg := range packageSuggestions {
insertText := fmt.Sprintf("package %s", pkg.name)
items = append(items, CompletionItem{
Label: insertText,
Kind: protocol.ModuleCompletion,
InsertText: insertText,
Score: pkg.score,
})
}
return items, surrounding, nil
}
// packageCompletionSurrounding returns surrounding for package completion if a
// package completions can be suggested at a given position. A valid location
// for package completion is above any declarations or import statements.
func packageCompletionSurrounding(fset *token.FileSet, fh source.FileHandle, pgf *source.ParsedGoFile, pos token.Pos) (*Selection, error) {
src, err := fh.Read()
if err != nil {
return nil, err
}
// If the file lacks a package declaration, the parser will return an empty
// AST. As a work-around, try to parse an expression from the file contents.
expr, _ := parser.ParseExprFrom(fset, fh.URI().Filename(), src, parser.Mode(0))
if expr == nil {
return nil, fmt.Errorf("unparseable file (%s)", fh.URI())
}
tok := fset.File(expr.Pos())
cursor := tok.Pos(pgf.Tok.Offset(pos))
m := &protocol.ColumnMapper{
URI: pgf.URI,
Content: src,
Converter: span.NewContentConverter(fh.URI().Filename(), src),
}
// If we were able to parse out an identifier as the first expression from
// the file, it may be the beginning of a package declaration ("pack ").
// We can offer package completions if the cursor is in the identifier.
if name, ok := expr.(*ast.Ident); ok {
if cursor >= name.Pos() && cursor <= name.End() {
if !strings.HasPrefix(PACKAGE, name.Name) {
return nil, fmt.Errorf("cursor in non-matching ident")
}
return &Selection{
content: name.Name,
cursor: cursor,
MappedRange: source.NewMappedRange(fset, m, name.Pos(), name.End()),
}, nil
}
}
// The file is invalid, but it contains an expression that we were able to
// parse. We will use this expression to construct the cursor's
// "surrounding".
// First, consider the possibility that we have a valid "package" keyword
// with an empty package name ("package "). "package" is parsed as an
// *ast.BadDecl since it is a keyword. This logic would allow "package" to
// appear on any line of the file as long as it's the first code expression
// in the file.
lines := strings.Split(string(src), "\n")
cursorLine := tok.Line(cursor)
if cursorLine <= 0 || cursorLine > len(lines) {
return nil, fmt.Errorf("invalid line number")
}
if fset.Position(expr.Pos()).Line == cursorLine {
words := strings.Fields(lines[cursorLine-1])
if len(words) > 0 && words[0] == PACKAGE {
content := PACKAGE
// Account for spaces if there are any.
if len(words) > 1 {
content += " "
}
start := expr.Pos()
end := token.Pos(int(expr.Pos()) + len(content) + 1)
// We have verified that we have a valid 'package' keyword as our
// first expression. Ensure that cursor is in this keyword or
// otherwise fallback to the general case.
if cursor >= start && cursor <= end {
return &Selection{
content: content,
cursor: cursor,
MappedRange: source.NewMappedRange(fset, m, start, end),
}, nil
}
}
}
// If the cursor is after the start of the expression, no package
// declaration will be valid.
if cursor > expr.Pos() {
return nil, fmt.Errorf("cursor after expression")
}
// If the cursor is in a comment, don't offer any completions.
if cursorInComment(fset, cursor, src) {
return nil, fmt.Errorf("cursor in comment")
}
// The surrounding range in this case is the cursor except for empty file,
// in which case it's end of file - 1
start, end := cursor, cursor
if tok.Size() == 0 {
start, end = tok.Pos(0)-1, tok.Pos(0)-1
}
return &Selection{
content: "",
cursor: cursor,
MappedRange: source.NewMappedRange(fset, m, start, end),
}, nil
}
func cursorInComment(fset *token.FileSet, cursor token.Pos, src []byte) bool {
var s scanner.Scanner
s.Init(fset.File(cursor), src, func(_ token.Position, _ string) {}, scanner.ScanComments)
for {
pos, tok, lit := s.Scan()
if pos <= cursor && cursor <= token.Pos(int(pos)+len(lit)) {
return tok == token.COMMENT
}
if tok == token.EOF {
break
}
}
return false
}
// packageNameCompletions returns name completions for a package clause using
// the current name as prefix.
func (c *completer) packageNameCompletions(ctx context.Context, fileURI span.URI, name *ast.Ident) error {
cursor := int(c.pos - name.NamePos)
if cursor < 0 || cursor > len(name.Name) {
return errors.New("cursor is not in package name identifier")
}
c.completionContext.packageCompletion = true
prefix := name.Name[:cursor]
packageSuggestions, err := packageSuggestions(ctx, c.snapshot, fileURI, prefix)
if err != nil {
return err
}
for _, pkg := range packageSuggestions {
c.deepState.enqueue(pkg)
}
return nil
}
// packageSuggestions returns a list of packages from workspace packages that
// have the given prefix and are used in the same directory as the given
// file. This also includes test packages for these packages (<pkg>_test) and
// the directory name itself.
func packageSuggestions(ctx context.Context, snapshot source.Snapshot, fileURI span.URI, prefix string) ([]candidate, error) {
workspacePackages, err := snapshot.WorkspacePackages(ctx)
if err != nil {
return nil, err
}
dirPath := filepath.Dir(string(fileURI))
dirName := filepath.Base(dirPath)
seenPkgs := make(map[string]struct{})
toCandidate := func(name string, score float64) candidate {
obj := types.NewPkgName(0, nil, name, types.NewPackage("", name))
return candidate{obj: obj, name: name, detail: name, score: score}
}
matcher := fuzzy.NewMatcher(prefix)
// The `go` command by default only allows one package per directory but we
// support multiple package suggestions since gopls is build system agnostic.
var packages []candidate
for _, pkg := range workspacePackages {
if pkg.Name() == "main" || pkg.Name() == "" {
continue
}
if _, ok := seenPkgs[pkg.Name()]; ok {
continue
}
// Only add packages that are previously used in the current directory.
var relevantPkg bool
for _, pgf := range pkg.CompiledGoFiles() {
if filepath.Dir(string(pgf.URI)) == dirPath {
relevantPkg = true
break
}
}
if !relevantPkg {
continue
}
// Add a found package used in current directory as a high relevance
// suggestion and the test package for it as a medium relevance
// suggestion.
if score := float64(matcher.Score(pkg.Name())); score > 0 {
packages = append(packages, toCandidate(pkg.Name(), score*highScore))
}
seenPkgs[pkg.Name()] = struct{}{}
testPkgName := pkg.Name() + "_test"
if _, ok := seenPkgs[testPkgName]; ok || strings.HasSuffix(pkg.Name(), "_test") {
continue
}
if score := float64(matcher.Score(testPkgName)); score > 0 {
packages = append(packages, toCandidate(testPkgName, score*stdScore))
}
seenPkgs[testPkgName] = struct{}{}
}
// Add current directory name as a low relevance suggestion.
if _, ok := seenPkgs[dirName]; !ok {
if score := float64(matcher.Score(dirName)); score > 0 {
packages = append(packages, toCandidate(dirName, score*lowScore))
}
testDirName := dirName + "_test"
if score := float64(matcher.Score(testDirName)); score > 0 {
packages = append(packages, toCandidate(testDirName, score*lowScore))
}
}
if score := float64(matcher.Score("main")); score > 0 {
packages = append(packages, toCandidate("main", score*lowScore))
}
return packages, nil
}