// 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
if rParenLine := fset.Position(d.Rparen).Line; rParenLine > lastLine+1 {
fset.File(d.Rparen).MergeLine(rParenLine - 1)
}
}
}
}
// NewCommentMap creates a new comment map by associating comment groups
// of the comments list with the nodes of the AST specified by node.
//
// A comment group g is associated with a node n if:
//
// - g starts on the same line as n ends
// - g starts on the line immediately following n, and there is
// at least one empty line after g and before the next node
// - g starts before n and is not associated to the node before n
// via the previous rules
//
// NewCommentMap tries to associate a comment group to the "largest"
// node possible: For instance, if the comment is a line comment
// trailing an assignment, the comment is associated with the entire
// assignment rather than just the last operand in the assignment.
//
func NewCommentMap(fset *token.FileSet, node Node, comments []*CommentGroup) CommentMap {
if len(comments) == 0 {
return nil // no comments to map
}
cmap := make(CommentMap)
// set up comment reader r
tmp := make([]*CommentGroup, len(comments))
copy(tmp, comments) // don't change incoming comments
sortComments(tmp)
r := commentListReader{fset: fset, list: tmp} // !r.eol() because len(comments) > 0
r.next()
// create node list in lexical order
nodes := nodeList(node)
nodes = append(nodes, nil) // append sentinel
// set up iteration variables
var (
p Node // previous node
pend token.Position // end of p
pg Node // previous node group (enclosing nodes of "importance")
pgend token.Position // end of pg
stack nodeStack // stack of node groups
)
for _, q := range nodes {
var qpos token.Position
if q != nil {
qpos = fset.Position(q.Pos()) // current node position
} else {
// set fake sentinel position to infinity so that
// all comments get processed before the sentinel
const infinity = 1 << 30
qpos.Offset = infinity
qpos.Line = infinity
}
// process comments before current node
for r.end.Offset <= qpos.Offset {
// determine recent node group
if top := stack.pop(r.comment.Pos()); top != nil {
pg = top
pgend = fset.Position(pg.End())
}
// Try to associate a comment first with a node group
// (i.e., a node of "importance" such as a declaration);
// if that fails, try to associate it with the most recent
// node.
// TODO(gri) try to simplify the logic below
var assoc Node
switch {
case pg != nil &&
(pgend.Line == r.pos.Line ||
pgend.Line+1 == r.pos.Line && r.end.Line+1 < qpos.Line):
// 1) comment starts on same line as previous node group ends, or
// 2) comment starts on the line immediately after the
// previous node group and there is an empty line before
// the current node
// => associate comment with previous node group
assoc = pg
case p != nil &&
(pend.Line == r.pos.Line ||
pend.Line+1 == r.pos.Line && r.end.Line+1 < qpos.Line ||
q == nil):
// same rules apply as above for p rather than pg,
// but also associate with p if we are at the end (q == nil)
assoc = p
default:
// otherwise, associate comment with current node
if q == nil {
// we can only reach here if there was no p
// which would imply that there were no nodes
panic("internal error: no comments should be associated with sentinel")
}
assoc = q
}
cmap.addComment(assoc, r.comment)
if r.eol() {
return cmap
}
r.next()
}
// update previous node
p = q
pend = fset.Position(p.End())
// update previous node group if we see an "important" node
switch q.(type) {
case *File, *Field, Decl, Spec, Stmt:
stack.push(q)
}
}
return cmap
}
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
}