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// Copyright 2019 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"
"go/ast"
"go/token"
"sort"
"strings"
"golang.org/x/tools/gopls/internal/lsp/protocol"
"golang.org/x/tools/internal/bug"
)
// FoldingRangeInfo holds range and kind info of folding for an ast.Node
type FoldingRangeInfo struct {
MappedRange protocol.MappedRange
Kind protocol.FoldingRangeKind
}
// FoldingRange gets all of the folding range for f.
func FoldingRange(ctx context.Context, snapshot Snapshot, fh FileHandle, lineFoldingOnly bool) (ranges []*FoldingRangeInfo, err error) {
// TODO(suzmue): consider limiting the number of folding ranges returned, and
// implement a way to prioritize folding ranges in that case.
pgf, err := snapshot.ParseGo(ctx, fh, ParseFull)
if err != nil {
return nil, err
}
// With parse errors, we wouldn't be able to produce accurate folding info.
// LSP protocol (3.16) currently does not have a way to handle this case
// (https://github.com/microsoft/language-server-protocol/issues/1200).
// We cannot return an error either because we are afraid some editors
// may not handle errors nicely. As a workaround, we now return an empty
// result and let the client handle this case by double check the file
// contents (i.e. if the file is not empty and the folding range result
// is empty, raise an internal error).
if pgf.ParseErr != nil {
return nil, nil
}
// Get folding ranges for comments separately as they are not walked by ast.Inspect.
ranges = append(ranges, commentsFoldingRange(pgf)...)
visit := func(n ast.Node) bool {
rng := foldingRangeFunc(pgf, n, lineFoldingOnly)
if rng != nil {
ranges = append(ranges, rng)
}
return true
}
// Walk the ast and collect folding ranges.
ast.Inspect(pgf.File, visit)
sort.Slice(ranges, func(i, j int) bool {
irng := ranges[i].MappedRange.Range()
jrng := ranges[j].MappedRange.Range()
return protocol.CompareRange(irng, jrng) < 0
})
return ranges, nil
}
// foldingRangeFunc calculates the line folding range for ast.Node n
func foldingRangeFunc(pgf *ParsedGoFile, n ast.Node, lineFoldingOnly bool) *FoldingRangeInfo {
// TODO(suzmue): include trailing empty lines before the closing
// parenthesis/brace.
var kind protocol.FoldingRangeKind
var start, end token.Pos
switch n := n.(type) {
case *ast.BlockStmt:
// Fold between positions of or lines between "{" and "}".
var startList, endList token.Pos
if num := len(n.List); num != 0 {
startList, endList = n.List[0].Pos(), n.List[num-1].End()
}
start, end = validLineFoldingRange(pgf.Tok, n.Lbrace, n.Rbrace, startList, endList, lineFoldingOnly)
case *ast.CaseClause:
// Fold from position of ":" to end.
start, end = n.Colon+1, n.End()
case *ast.CommClause:
// Fold from position of ":" to end.
start, end = n.Colon+1, n.End()
case *ast.CallExpr:
// Fold from position of "(" to position of ")".
start, end = n.Lparen+1, n.Rparen
case *ast.FieldList:
// Fold between positions of or lines between opening parenthesis/brace and closing parenthesis/brace.
var startList, endList token.Pos
if num := len(n.List); num != 0 {
startList, endList = n.List[0].Pos(), n.List[num-1].End()
}
start, end = validLineFoldingRange(pgf.Tok, n.Opening, n.Closing, startList, endList, lineFoldingOnly)
case *ast.GenDecl:
// If this is an import declaration, set the kind to be protocol.Imports.
if n.Tok == token.IMPORT {
kind = protocol.Imports
}
// Fold between positions of or lines between "(" and ")".
var startSpecs, endSpecs token.Pos
if num := len(n.Specs); num != 0 {
startSpecs, endSpecs = n.Specs[0].Pos(), n.Specs[num-1].End()
}
start, end = validLineFoldingRange(pgf.Tok, n.Lparen, n.Rparen, startSpecs, endSpecs, lineFoldingOnly)
case *ast.BasicLit:
// Fold raw string literals from position of "`" to position of "`".
if n.Kind == token.STRING && len(n.Value) >= 2 && n.Value[0] == '`' && n.Value[len(n.Value)-1] == '`' {
start, end = n.Pos(), n.End()
}
case *ast.CompositeLit:
// Fold between positions of or lines between "{" and "}".
var startElts, endElts token.Pos
if num := len(n.Elts); num != 0 {
startElts, endElts = n.Elts[0].Pos(), n.Elts[num-1].End()
}
start, end = validLineFoldingRange(pgf.Tok, n.Lbrace, n.Rbrace, startElts, endElts, lineFoldingOnly)
}
// Check that folding positions are valid.
if !start.IsValid() || !end.IsValid() {
return nil
}
// in line folding mode, do not fold if the start and end lines are the same.
if lineFoldingOnly && pgf.Tok.Line(start) == pgf.Tok.Line(end) {
return nil
}
mrng, err := pgf.PosMappedRange(start, end)
if err != nil {
bug.Errorf("%w", err) // can't happen
}
return &FoldingRangeInfo{
MappedRange: mrng,
Kind: kind,
}
}
// validLineFoldingRange returns start and end token.Pos for folding range if the range is valid.
// returns token.NoPos otherwise, which fails token.IsValid check
func validLineFoldingRange(tokFile *token.File, open, close, start, end token.Pos, lineFoldingOnly bool) (token.Pos, token.Pos) {
if lineFoldingOnly {
if !open.IsValid() || !close.IsValid() {
return token.NoPos, token.NoPos
}
// Don't want to fold if the start/end is on the same line as the open/close
// as an example, the example below should *not* fold:
// var x = [2]string{"d",
// "e" }
if tokFile.Line(open) == tokFile.Line(start) ||
tokFile.Line(close) == tokFile.Line(end) {
return token.NoPos, token.NoPos
}
return open + 1, end
}
return open + 1, close
}
// commentsFoldingRange returns the folding ranges for all comment blocks in file.
// The folding range starts at the end of the first line of the comment block, and ends at the end of the
// comment block and has kind protocol.Comment.
func commentsFoldingRange(pgf *ParsedGoFile) (comments []*FoldingRangeInfo) {
tokFile := pgf.Tok
for _, commentGrp := range pgf.File.Comments {
startGrpLine, endGrpLine := tokFile.Line(commentGrp.Pos()), tokFile.Line(commentGrp.End())
if startGrpLine == endGrpLine {
// Don't fold single line comments.
continue
}
firstComment := commentGrp.List[0]
startPos, endLinePos := firstComment.Pos(), firstComment.End()
startCmmntLine, endCmmntLine := tokFile.Line(startPos), tokFile.Line(endLinePos)
if startCmmntLine != endCmmntLine {
// If the first comment spans multiple lines, then we want to have the
// folding range start at the end of the first line.
endLinePos = token.Pos(int(startPos) + len(strings.Split(firstComment.Text, "\n")[0]))
}
mrng, err := pgf.PosMappedRange(endLinePos, commentGrp.End())
if err != nil {
bug.Errorf("%w", err) // can't happen
}
comments = append(comments, &FoldingRangeInfo{
// Fold from the end of the first line comment to the end of the comment block.
MappedRange: mrng,
Kind: protocol.Comment,
})
}
return comments
}
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