blob: 3c4ae69cd54e7741a1537fb2c2df19c601742fc4 [file] [log] [blame]
// 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/token"
"strings"
"golang.org/x/tools/go/ast/astutil"
"golang.org/x/tools/imports"
"golang.org/x/tools/internal/lsp/diff"
)
// Format formats a file with a given range.
func Format(ctx context.Context, f File, rng Range) ([]TextEdit, error) {
fAST := f.GetAST()
path, exact := astutil.PathEnclosingInterval(fAST, rng.Start, rng.End)
if !exact || len(path) == 0 {
return nil, fmt.Errorf("no exact AST node matching the specified range")
}
node := path[0]
// format.Node can fail when the AST contains a bad expression or
// statement. For now, we preemptively check for one.
// TODO(rstambler): This should really return an error from format.Node.
var isBad bool
ast.Inspect(node, func(n ast.Node) bool {
switch n.(type) {
case *ast.BadDecl, *ast.BadExpr, *ast.BadStmt:
isBad = true
return false
default:
return true
}
})
if isBad {
return nil, fmt.Errorf("unable to format file due to a badly formatted AST")
}
// 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.
fset := f.GetFileSet()
buf := &bytes.Buffer{}
if err := format.Node(buf, fset, node); err != nil {
return nil, err
}
return computeTextEdits(rng, f, buf.String()), nil
}
// Imports formats a file using the goimports tool.
func Imports(ctx context.Context, f File, rng Range) ([]TextEdit, error) {
formatted, err := imports.Process(f.GetToken().Name(), f.GetContent(), nil)
if err != nil {
return nil, err
}
return computeTextEdits(rng, f, string(formatted)), nil
}
func computeTextEdits(rng Range, file File, formatted string) (edits []TextEdit) {
u := strings.SplitAfter(string(file.GetContent()), "\n")
tok := file.GetToken()
f := strings.SplitAfter(formatted, "\n")
for _, op := range diff.Operations(u, f) {
start := lineStart(tok, op.I1+1)
if start == token.NoPos && op.I1 == len(u) {
start = tok.Pos(tok.Size())
}
end := lineStart(tok, op.I2+1)
if end == token.NoPos && op.I2 == len(u) {
end = tok.Pos(tok.Size())
}
switch op.Kind {
case diff.Delete:
// Delete: unformatted[i1:i2] is deleted.
edits = append(edits, TextEdit{
Range: Range{
Start: start,
End: end,
},
})
case diff.Insert:
// Insert: formatted[j1:j2] is inserted at unformatted[i1:i1].
edits = append(edits, TextEdit{
Range: Range{
Start: start,
End: start,
},
NewText: op.Content,
})
}
}
return edits
}