// Copyright 2011 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 ast import ( "go/token" "sort" "strconv" ) // SortImports sorts runs of consecutive import lines in import blocks in f. // It also removes duplicate imports when it is possible to do so without data loss. func SortImports(fset *token.FileSet, f *File) { for _, d := range f.Decls { d, ok := d.(*GenDecl) if !ok || d.Tok != token.IMPORT { // Not an import declaration, so we're done. // Imports are always first. break } if !d.Lparen.IsValid() { // Not a block: sorted by default. continue } // Identify and sort runs of specs on successive lines. i := 0 specs := d.Specs[:0] for j, s := range d.Specs { if j > i && fset.Position(s.Pos()).Line > 1+fset.Position(d.Specs[j-1].End()).Line { // j begins a new run. End this one. specs = append(specs, sortSpecs(fset, f, d.Specs[i:j])...) i = j } } specs = append(specs, sortSpecs(fset, f, d.Specs[i:])...) d.Specs = specs // Deduping can leave a blank line before the rparen; clean that up. if len(d.Specs) > 0 { lastSpec := d.Specs[len(d.Specs)-1] lastLine := fset.Position(lastSpec.Pos()).Line rParenLine := fset.Position(d.Rparen).Line for rParenLine > lastLine+1 { rParenLine-- fset.File(d.Rparen).MergeLine(rParenLine) } } } } func importPath(s Spec) string { t, err := strconv.Unquote(s.(*ImportSpec).Path.Value) if err == nil { return t } return "" } func importName(s Spec) string { n := s.(*ImportSpec).Name if n == nil { return "" } return n.Name } func importComment(s Spec) string { c := s.(*ImportSpec).Comment if c == nil { return "" } return c.Text() } // collapse indicates whether prev may be removed, leaving only next. func collapse(prev, next Spec) bool { if importPath(next) != importPath(prev) || importName(next) != importName(prev) { return false } return prev.(*ImportSpec).Comment == nil } type posSpan struct { Start token.Pos End token.Pos } func sortSpecs(fset *token.FileSet, f *File, specs []Spec) []Spec { // Can't short-circuit here even if specs are already sorted, // since they might yet need deduplication. // A lone import, however, may be safely ignored. if len(specs) <= 1 { return specs } // Record positions for specs. pos := make([]posSpan, len(specs)) for i, s := range specs { pos[i] = posSpan{s.Pos(), s.End()} } // Identify comments in this range. // Any comment from pos[0].Start to the final line counts. lastLine := fset.Position(pos[len(pos)-1].End).Line cstart := len(f.Comments) cend := len(f.Comments) for i, g := range f.Comments { if g.Pos() < pos[0].Start { continue } if i < cstart { cstart = i } if fset.Position(g.End()).Line > lastLine { cend = i break } } comments := f.Comments[cstart:cend] // Assign each comment to the import spec preceding it. importComment := map[*ImportSpec][]*CommentGroup{} specIndex := 0 for _, g := range comments { for specIndex+1 < len(specs) && pos[specIndex+1].Start <= g.Pos() { specIndex++ } s := specs[specIndex].(*ImportSpec) importComment[s] = append(importComment[s], g) } // Sort the import specs by import path. // Remove duplicates, when possible without data loss. // Reassign the import paths to have the same position sequence. // Reassign each comment to abut the end of its spec. // Sort the comments by new position. sort.Sort(byImportSpec(specs)) // Dedup. Thanks to our sorting, we can just consider // adjacent pairs of imports. deduped := specs[:0] for i, s := range specs { if i == len(specs)-1 || !collapse(s, specs[i+1]) { deduped = append(deduped, s) } else { p := s.Pos() fset.File(p).MergeLine(fset.Position(p).Line) } } specs = deduped // Fix up comment positions for i, s := range specs { s := s.(*ImportSpec) if s.Name != nil { s.Name.NamePos = pos[i].Start } s.Path.ValuePos = pos[i].Start s.EndPos = pos[i].End for _, g := range importComment[s] { for _, c := range g.List { c.Slash = pos[i].End } } } sort.Sort(byCommentPos(comments)) return specs } type byImportSpec []Spec // slice of *ImportSpec func (x byImportSpec) Len() int { return len(x) } func (x byImportSpec) Swap(i, j int) { x[i], x[j] = x[j], x[i] } func (x byImportSpec) Less(i, j int) bool { ipath := importPath(x[i]) jpath := importPath(x[j]) if ipath != jpath { return ipath < jpath } iname := importName(x[i]) jname := importName(x[j]) if iname != jname { return iname < jname } return importComment(x[i]) < importComment(x[j]) } type byCommentPos []*CommentGroup func (x byCommentPos) Len() int { return len(x) } func (x byCommentPos) Swap(i, j int) { x[i], x[j] = x[j], x[i] } func (x byCommentPos) Less(i, j int) bool { return x[i].Pos() < x[j].Pos() }