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 // Copyright 2012 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 ( "bytes" "fmt" "go/token" "sort" ) type byPos []*CommentGroup func (a byPos) Len() int { return len(a) } func (a byPos) Less(i, j int) bool { return a[i].Pos() < a[j].Pos() } func (a byPos) Swap(i, j int) { a[i], a[j] = a[j], a[i] } // sortComments sorts the list of comment groups in source order. // func sortComments(list []*CommentGroup) { // TODO(gri): Does it make sense to check for sorted-ness // first (because we know that sorted-ness is // very likely)? if orderedList := byPos(list); !sort.IsSorted(orderedList) { sort.Sort(orderedList) } } // A CommentMap maps an AST node to a list of comment groups // associated with it. See NewCommentMap for a description of // the association. // type CommentMap map[Node][]*CommentGroup func (cmap CommentMap) addComment(n Node, c *CommentGroup) { list := cmap[n] if len(list) == 0 { list = []*CommentGroup{c} } else { list = append(list, c) } cmap[n] = list } type byInterval []Node func (a byInterval) Len() int { return len(a) } func (a byInterval) Less(i, j int) bool { pi, pj := a[i].Pos(), a[j].Pos() return pi < pj || pi == pj && a[i].End() > a[j].End() } func (a byInterval) Swap(i, j int) { a[i], a[j] = a[j], a[i] } // nodeList returns the list of nodes of the AST n in source order. // func nodeList(n Node) []Node { var list []Node Inspect(n, func(n Node) bool { // don't collect comments switch n.(type) { case nil, *CommentGroup, *Comment: return false } list = append(list, n) return true }) // Note: The current implementation assumes that Inspect traverses the // AST in depth-first and thus _source_ order. If AST traversal // does not follow source order, the sorting call below will be // required. // sort.Sort(byInterval(list)) return list } // A commentListReader helps iterating through a list of comment groups. // type commentListReader struct { fset *token.FileSet list []*CommentGroup index int comment *CommentGroup // comment group at current index pos, end token.Position // source interval of comment group at current index } func (r *commentListReader) eol() bool { return r.index >= len(r.list) } func (r *commentListReader) next() { if !r.eol() { r.comment = r.list[r.index] r.pos = r.fset.Position(r.comment.Pos()) r.end = r.fset.Position(r.comment.End()) r.index++ } } // A nodeStack keeps track of nested nodes. // A node lower on the stack lexically contains the nodes higher on the stack. // type nodeStack []Node // push pops all nodes that appear lexically before n // and then pushes n on the stack. // func (s *nodeStack) push(n Node) { s.pop(n.Pos()) *s = append((*s), n) } // pop pops all nodes that appear lexically before pos // (i.e., whose lexical extent has ended before or at pos). // It returns the last node popped. // func (s *nodeStack) pop(pos token.Pos) (top Node) { i := len(*s) for i > 0 && (*s)[i-1].End() <= pos { top = (*s)[i-1] i-- } *s = (*s)[0:i] return top } // 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 } // Update replaces an old node in the comment map with the new node // and returns the new node. Comments that were associated with the // old node are associated with the new node. // func (cmap CommentMap) Update(old, new Node) Node { if list := cmap[old]; len(list) > 0 { delete(cmap, old) cmap[new] = append(cmap[new], list...) } return new } // Filter returns a new comment map consisting of only those // entries of cmap for which a corresponding node exists in // the AST specified by node. // func (cmap CommentMap) Filter(node Node) CommentMap { umap := make(CommentMap) Inspect(node, func(n Node) bool { if g := cmap[n]; len(g) > 0 { umap[n] = g } return true }) return umap } // Comments returns the list of comment groups in the comment map. // The result is sorted in source order. // func (cmap CommentMap) Comments() []*CommentGroup { list := make([]*CommentGroup, 0, len(cmap)) for _, e := range cmap { list = append(list, e...) } sortComments(list) return list } func summary(list []*CommentGroup) string { const maxLen = 40 var buf bytes.Buffer // collect comments text loop: for _, group := range list { // Note: CommentGroup.Text() does too much work for what we // need and would only replace this innermost loop. // Just do it explicitly. for _, comment := range group.List { if buf.Len() >= maxLen { break loop } buf.WriteString(comment.Text) } } // truncate if too long if buf.Len() > maxLen { buf.Truncate(maxLen - 3) buf.WriteString("...") } // replace any invisibles with blanks bytes := buf.Bytes() for i, b := range bytes { switch b { case '\t', '\n', '\r': bytes[i] = ' ' } } return string(bytes) } func (cmap CommentMap) String() string { var buf bytes.Buffer fmt.Fprintln(&buf, "CommentMap {") for node, comment := range cmap { // print name of identifiers; print node type for other nodes var s string if ident, ok := node.(*Ident); ok { s = ident.Name } else { s = fmt.Sprintf("%T", node) } fmt.Fprintf(&buf, "\t%p %20s: %s\n", node, s, summary(comment)) } fmt.Fprintln(&buf, "}") return buf.String() }