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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 source provides core features for use by Go editors and tools.
package source
import (
"bytes"
"context"
"fmt"
"go/ast"
"go/format"
"go/parser"
"go/token"
"strings"
"golang.org/x/tools/internal/event"
"golang.org/x/tools/internal/imports"
"golang.org/x/tools/internal/lsp/diff"
"golang.org/x/tools/internal/lsp/protocol"
)
// Format formats a file with a given range.
func Format(ctx context.Context, snapshot Snapshot, fh FileHandle) ([]protocol.TextEdit, error) {
ctx, done := event.Start(ctx, "source.Format")
defer done()
pgf, err := snapshot.ParseGo(ctx, fh, ParseFull)
if err != nil {
return nil, err
}
// Even if this file has parse errors, it might still be possible to format it.
// Using format.Node on an AST with errors may result in code being modified.
// Attempt to format the source of this file instead.
if pgf.ParseErr != nil {
formatted, err := formatSource(ctx, fh)
if err != nil {
return nil, err
}
return computeTextEdits(ctx, snapshot, pgf, string(formatted))
}
fset := snapshot.FileSet()
// format.Node changes slightly from one release to another, so the version
// of Go used to build the LSP server will determine how it formats code.
// This should be acceptable for all users, who likely be prompted to rebuild
// the LSP server on each Go release.
buf := &bytes.Buffer{}
if err := format.Node(buf, fset, pgf.File); err != nil {
return nil, err
}
formatted := buf.String()
// Apply additional formatting, if any is supported. Currently, the only
// supported additional formatter is gofumpt.
if format := snapshot.View().Options().Hooks.GofumptFormat; snapshot.View().Options().Gofumpt && format != nil {
b, err := format(ctx, buf.Bytes())
if err != nil {
return nil, err
}
formatted = string(b)
}
return computeTextEdits(ctx, snapshot, pgf, formatted)
}
func formatSource(ctx context.Context, fh FileHandle) ([]byte, error) {
_, done := event.Start(ctx, "source.formatSource")
defer done()
data, err := fh.Read()
if err != nil {
return nil, err
}
return format.Source(data)
}
type ImportFix struct {
Fix *imports.ImportFix
Edits []protocol.TextEdit
}
// AllImportsFixes formats f for each possible fix to the imports.
// In addition to returning the result of applying all edits,
// it returns a list of fixes that could be applied to the file, with the
// corresponding TextEdits that would be needed to apply that fix.
func AllImportsFixes(ctx context.Context, snapshot Snapshot, fh FileHandle) (allFixEdits []protocol.TextEdit, editsPerFix []*ImportFix, err error) {
ctx, done := event.Start(ctx, "source.AllImportsFixes")
defer done()
pgf, err := snapshot.ParseGo(ctx, fh, ParseFull)
if err != nil {
return nil, nil, err
}
if err := snapshot.View().RunProcessEnvFunc(ctx, func(opts *imports.Options) error {
allFixEdits, editsPerFix, err = computeImportEdits(ctx, snapshot, pgf, opts)
return err
}); err != nil {
return nil, nil, fmt.Errorf("AllImportsFixes: %v", err)
}
return allFixEdits, editsPerFix, nil
}
// computeImportEdits computes a set of edits that perform one or all of the
// necessary import fixes.
func computeImportEdits(ctx context.Context, snapshot Snapshot, pgf *ParsedGoFile, options *imports.Options) (allFixEdits []protocol.TextEdit, editsPerFix []*ImportFix, err error) {
filename := pgf.URI.Filename()
// Build up basic information about the original file.
allFixes, err := imports.FixImports(filename, pgf.Src, options)
if err != nil {
return nil, nil, err
}
allFixEdits, err = computeFixEdits(snapshot, pgf, options, allFixes)
if err != nil {
return nil, nil, err
}
// Apply all of the import fixes to the file.
// Add the edits for each fix to the result.
for _, fix := range allFixes {
edits, err := computeFixEdits(snapshot, pgf, options, []*imports.ImportFix{fix})
if err != nil {
return nil, nil, err
}
editsPerFix = append(editsPerFix, &ImportFix{
Fix: fix,
Edits: edits,
})
}
return allFixEdits, editsPerFix, nil
}
// ComputeOneImportFixEdits returns text edits for a single import fix.
func ComputeOneImportFixEdits(ctx context.Context, snapshot Snapshot, pgf *ParsedGoFile, fix *imports.ImportFix) ([]protocol.TextEdit, error) {
options := &imports.Options{
LocalPrefix: snapshot.View().Options().Local,
// Defaults.
AllErrors: true,
Comments: true,
Fragment: true,
FormatOnly: false,
TabIndent: true,
TabWidth: 8,
}
return computeFixEdits(snapshot, pgf, options, []*imports.ImportFix{fix})
}
func computeFixEdits(snapshot Snapshot, pgf *ParsedGoFile, options *imports.Options, fixes []*imports.ImportFix) ([]protocol.TextEdit, error) {
// trim the original data to match fixedData
left := importPrefix(pgf.Src)
extra := !strings.Contains(left, "\n") // one line may have more than imports
if extra {
left = string(pgf.Src)
}
if len(left) > 0 && left[len(left)-1] != '\n' {
left += "\n"
}
// Apply the fixes and re-parse the file so that we can locate the
// new imports.
flags := parser.ImportsOnly
if extra {
// used all of origData above, use all of it here too
flags = 0
}
fixedData, err := imports.ApplyFixes(fixes, "", pgf.Src, options, flags)
if err != nil {
return nil, err
}
if fixedData == nil || fixedData[len(fixedData)-1] != '\n' {
fixedData = append(fixedData, '\n') // ApplyFixes may miss the newline, go figure.
}
edits := snapshot.View().Options().ComputeEdits(pgf.URI, left, string(fixedData))
return ToProtocolEdits(pgf.Mapper, edits)
}
// importPrefix returns the prefix of the given file content through the final
// import statement. If there are no imports, the prefix is the package
// statement and any comment groups below it.
func importPrefix(src []byte) string {
fset := token.NewFileSet()
// do as little parsing as possible
f, err := parser.ParseFile(fset, "", src, parser.ImportsOnly|parser.ParseComments)
if err != nil { // This can happen if 'package' is misspelled
return ""
}
tok := fset.File(f.Pos())
var importEnd int
for _, d := range f.Decls {
if x, ok := d.(*ast.GenDecl); ok && x.Tok == token.IMPORT {
if e := tok.Offset(d.End()); e > importEnd {
importEnd = e
}
}
}
maybeAdjustToLineEnd := func(pos token.Pos, isCommentNode bool) int {
offset := tok.Offset(pos)
// Don't go past the end of the file.
if offset > len(src) {
offset = len(src)
}
// The go/ast package does not account for different line endings, and
// specifically, in the text of a comment, it will strip out \r\n line
// endings in favor of \n. To account for these differences, we try to
// return a position on the next line whenever possible.
switch line := tok.Line(tok.Pos(offset)); {
case line < tok.LineCount():
nextLineOffset := tok.Offset(tok.LineStart(line + 1))
// If we found a position that is at the end of a line, move the
// offset to the start of the next line.
if offset+1 == nextLineOffset {
offset = nextLineOffset
}
case isCommentNode, offset+1 == tok.Size():
// If the last line of the file is a comment, or we are at the end
// of the file, the prefix is the entire file.
offset = len(src)
}
return offset
}
if importEnd == 0 {
pkgEnd := f.Name.End()
importEnd = maybeAdjustToLineEnd(pkgEnd, false)
}
for _, c := range f.Comments {
if end := tok.Offset(c.End()); end > importEnd {
// Work-around golang/go#41197: For multi-line comments add +2 to
// the offset. The end position does not account for the */ at the
// end.
endLine := tok.Position(c.End()).Line
if end+2 <= tok.Size() && tok.Position(tok.Pos(end+2)).Line == endLine {
end += 2
}
importEnd = maybeAdjustToLineEnd(tok.Pos(end), true)
}
}
if importEnd > len(src) {
importEnd = len(src)
}
return string(src[:importEnd])
}
func computeTextEdits(ctx context.Context, snapshot Snapshot, pgf *ParsedGoFile, formatted string) ([]protocol.TextEdit, error) {
_, done := event.Start(ctx, "source.computeTextEdits")
defer done()
edits := snapshot.View().Options().ComputeEdits(pgf.URI, string(pgf.Src), formatted)
return ToProtocolEdits(pgf.Mapper, edits)
}
func ToProtocolEdits(m *protocol.ColumnMapper, edits []diff.TextEdit) ([]protocol.TextEdit, error) {
if edits == nil {
return nil, nil
}
result := make([]protocol.TextEdit, len(edits))
for i, edit := range edits {
rng, err := m.Range(edit.Span)
if err != nil {
return nil, err
}
result[i] = protocol.TextEdit{
Range: rng,
NewText: edit.NewText,
}
}
return result, nil
}
func FromProtocolEdits(m *protocol.ColumnMapper, edits []protocol.TextEdit) ([]diff.TextEdit, error) {
if edits == nil {
return nil, nil
}
result := make([]diff.TextEdit, len(edits))
for i, edit := range edits {
spn, err := m.RangeSpan(edit.Range)
if err != nil {
return nil, err
}
result[i] = diff.TextEdit{
Span: spn,
NewText: edit.NewText,
}
}
return result, nil
}