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Diffstat (limited to '')
| -rw-r--r-- | src/go/ast/import.go | 230 |
1 files changed, 230 insertions, 0 deletions
diff --git a/src/go/ast/import.go b/src/go/ast/import.go new file mode 100644 index 0000000..7fdf137 --- /dev/null +++ b/src/go/ast/import.go @@ -0,0 +1,230 @@ +// 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 && lineAt(fset, s.Pos()) > 1+lineAt(fset, d.Specs[j-1].End()) { + // 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 := lineAt(fset, lastSpec.Pos()) + rParenLine := lineAt(fset, d.Rparen) + for rParenLine > lastLine+1 { + rParenLine-- + fset.File(d.Rparen).MergeLine(rParenLine) + } + } + } +} + +func lineAt(fset *token.FileSet, pos token.Pos) int { + return fset.PositionFor(pos, false).Line +} + +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 +} + +type cgPos struct { + left bool // true if comment is to the left of the spec, false otherwise. + cg *CommentGroup +} + +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. + begSpecs := pos[0].Start + endSpecs := pos[len(pos)-1].End + beg := fset.File(begSpecs).LineStart(lineAt(fset, begSpecs)) + endLine := lineAt(fset, endSpecs) + endFile := fset.File(endSpecs) + var end token.Pos + if endLine == endFile.LineCount() { + end = endSpecs + } else { + end = endFile.LineStart(endLine + 1) // beginning of next line + } + first := len(f.Comments) + last := -1 + for i, g := range f.Comments { + if g.End() >= end { + break + } + // g.End() < end + if beg <= g.Pos() { + // comment is within the range [beg, end[ of import declarations + if i < first { + first = i + } + if i > last { + last = i + } + } + } + + var comments []*CommentGroup + if last >= 0 { + comments = f.Comments[first : last+1] + } + + // Assign each comment to the import spec on the same line. + importComments := map[*ImportSpec][]cgPos{} + specIndex := 0 + for _, g := range comments { + for specIndex+1 < len(specs) && pos[specIndex+1].Start <= g.Pos() { + specIndex++ + } + var left bool + // A block comment can appear before the first import spec. + if specIndex == 0 && pos[specIndex].Start > g.Pos() { + left = true + } else if specIndex+1 < len(specs) && // Or it can appear on the left of an import spec. + lineAt(fset, pos[specIndex].Start)+1 == lineAt(fset, g.Pos()) { + specIndex++ + left = true + } + s := specs[specIndex].(*ImportSpec) + importComments[s] = append(importComments[s], cgPos{left: left, cg: 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 the spec on the same line. + // Sort the comments by new position. + sort.Slice(specs, func(i, j int) bool { + ipath := importPath(specs[i]) + jpath := importPath(specs[j]) + if ipath != jpath { + return ipath < jpath + } + iname := importName(specs[i]) + jname := importName(specs[j]) + if iname != jname { + return iname < jname + } + return importComment(specs[i]) < importComment(specs[j]) + }) + + // 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(lineAt(fset, p)) + } + } + 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 importComments[s] { + for _, c := range g.cg.List { + if g.left { + c.Slash = pos[i].Start - 1 + } else { + // An import spec can have both block comment and a line comment + // to its right. In that case, both of them will have the same pos. + // But while formatting the AST, the line comment gets moved to + // after the block comment. + c.Slash = pos[i].End + } + } + } + } + + sort.Slice(comments, func(i, j int) bool { + return comments[i].Pos() < comments[j].Pos() + }) + + return specs +} |