go/printer: use general comment intersperse mechanism everywhere

- remove several TODOs
- as a side-effect, comment stylers are now used always and comments
  will be properly colored in godoc pkg documentation pages (and not
  only when looking at source text)

R=rsc
CC=golang-dev
https://golang.org/cl/222041

5 files changed, 77 insertions, 69 deletions

diff --git a/src/pkg/go/printer/nodes.go b/src/pkg/go/printer/nodes.go
index e2cc249484..dd6b1db6b2 100644
--- a/src/pkg/go/printer/nodes.go
+++ b/src/pkg/go/printer/nodes.go
@@ -12,6 +12,7 @@ import (
 	"bytes"
 	"go/ast"
 	"go/token"
+	"strings"
 )
 
 
@@ -59,43 +60,25 @@ func (p *printer) linebreak(line, min, max int, ws whiteSpace, newSection bool)
 }
 
 
-// TODO(gri): The code for printing lead and line comments
-//            should be eliminated in favor of reusing the
-//            comment intersperse mechanism above somehow.
-
-// Print a list of individual comments.
-func (p *printer) commentList(list []*ast.Comment) {
-	for i, c := range list {
-		t := c.Text
-		// TODO(gri): this needs to be styled like normal comments
-		p.print(c.Pos(), t)
-		if t[1] == '/' && i+1 < len(list) {
-			//-style comment which is not at the end; print a newline
-			p.print(newline)
-		}
+// setComment sets g as the next comment if g != nil and if node comments
+// are enabled - this mode is used when printing source code fragments such
+// as exports only. It assumes that there are no other pending comments to
+// intersperse.
+func (p *printer) setComment(g *ast.CommentGroup) {
+	if g == nil || !p.useNodeComments {
+		return
 	}
-}
-
-
-// Print a lead comment followed by a newline.
-func (p *printer) leadComment(d *ast.CommentGroup) {
-	// Ignore the comment if we have comments interspersed (p.comment != nil).
-	if p.comments == nil && d != nil {
-		p.commentList(d.List)
-		p.print(newline)
-	}
-}
-
-
-// Print a tab followed by a line comment.
-// A newline must be printed afterwards since
-// the comment may be a //-style comment.
-func (p *printer) lineComment(d *ast.CommentGroup) {
-	// Ignore the comment if we have comments interspersed (p.comment != nil).
-	if p.comments == nil && d != nil {
-		p.print(vtab)
-		p.commentList(d.List)
+	if p.comments == nil {
+		// initialize p.comments lazily
+		p.comments = make([]*ast.CommentGroup, 1)
+	} else if p.cindex < len(p.comments) {
+		// for some reason there are pending comments; this
+		// should never happen - handle gracefully and flush
+		// all comments up to g, ignore anything after that
+		p.flush(g.List[0].Pos(), false)
 	}
+	p.comments[0] = g
+	p.cindex = 0
 }
 
 
@@ -307,6 +290,11 @@ func (p *printer) isOneLineFieldList(list []*ast.Field) bool {
 }
 
 
+func (p *printer) setLineComment(text string) {
+	p.setComment(&ast.CommentGroup{[]*ast.Comment{&ast.Comment{noPos, strings.Bytes(text)}}})
+}
+
+
 func (p *printer) fieldList(lbrace token.Position, list []*ast.Field, rbrace token.Position, isIncomplete bool, ctxt exprContext) {
 	if !isIncomplete && !p.commentBefore(rbrace) {
 		// possibly a one-line struct/interface
@@ -350,7 +338,7 @@ func (p *printer) fieldList(lbrace token.Position, list []*ast.Field, rbrace tok
 			}
 			ml = false
 			extraTabs := 0
-			p.leadComment(f.Doc)
+			p.setComment(f.Doc)
 			if len(f.Names) > 0 {
 				// named fields
 				p.identList(f.Names, &ml)
@@ -372,17 +360,17 @@ func (p *printer) fieldList(lbrace token.Position, list []*ast.Field, rbrace tok
 			}
 			if f.Comment != nil {
 				for ; extraTabs > 0; extraTabs-- {
-					p.print(vtab)
+					p.print(sep)
 				}
-				p.lineComment(f.Comment)
+				p.setComment(f.Comment)
 			}
 		}
 		if isIncomplete {
 			if len(list) > 0 {
 				p.print(formfeed)
 			}
-			// TODO(gri): this needs to be styled like normal comments
-			p.print("// contains unexported fields")
+			p.flush(rbrace, false) // make sure we don't loose the last line comment
+			p.setLineComment("// contains unexported fields")
 		}
 
 	} else { // interface
@@ -393,7 +381,7 @@ func (p *printer) fieldList(lbrace token.Position, list []*ast.Field, rbrace tok
 				p.linebreak(f.Pos().Line, 1, 2, ignore, ml)
 			}
 			ml = false
-			p.leadComment(f.Doc)
+			p.setComment(f.Doc)
 			if ftyp, isFtyp := f.Type.(*ast.FuncType); isFtyp {
 				// method
 				p.expr(f.Names[0], &ml)
@@ -402,14 +390,14 @@ func (p *printer) fieldList(lbrace token.Position, list []*ast.Field, rbrace tok
 				// embedded interface
 				p.expr(f.Type, &ml)
 			}
-			p.lineComment(f.Comment)
+			p.setComment(f.Comment)
 		}
 		if isIncomplete {
 			if len(list) > 0 {
 				p.print(formfeed)
 			}
-			// TODO(gri): this needs to be styled like normal comments
-			p.print("// contains unexported methods")
+			p.flush(rbrace, false) // make sure we don't loose the last line comment
+			p.setLineComment("// contains unexported methods")
 		}
 
 	}
@@ -1052,7 +1040,7 @@ func (p *printer) spec(spec ast.Spec, n int, context declContext, multiLine *boo
 
 	switch s := spec.(type) {
 	case *ast.ImportSpec:
-		p.leadComment(s.Doc)
+		p.setComment(s.Doc)
 		if s.Name != nil {
 			p.expr(s.Name, multiLine)
 			p.print(blank)
@@ -1061,7 +1049,7 @@ func (p *printer) spec(spec ast.Spec, n int, context declContext, multiLine *boo
 		comment = s.Comment
 
 	case *ast.ValueSpec:
-		p.leadComment(s.Doc)
+		p.setComment(s.Doc)
 		p.identList(s.Names, multiLine) // always present
 		if n == 1 {
 			if s.Type != nil {
@@ -1091,7 +1079,7 @@ func (p *printer) spec(spec ast.Spec, n int, context declContext, multiLine *boo
 		comment = s.Comment
 
 	case *ast.TypeSpec:
-		p.leadComment(s.Doc)
+		p.setComment(s.Doc)
 		p.expr(s.Name, multiLine)
 		if n == 1 {
 			p.print(blank)
@@ -1109,14 +1097,14 @@ func (p *printer) spec(spec ast.Spec, n int, context declContext, multiLine *boo
 		for ; extraTabs > 0; extraTabs-- {
 			p.print(vtab)
 		}
-		p.lineComment(comment)
+		p.setComment(comment)
 	}
 }
 
 
 // Sets multiLine to true if the declaration spans multiple lines.
 func (p *printer) genDecl(d *ast.GenDecl, context declContext, multiLine *bool) {
-	p.leadComment(d.Doc)
+	p.setComment(d.Doc)
 	p.print(d.Pos(), d.Tok, blank)
 
 	if d.Lparen.IsValid() {
@@ -1225,7 +1213,7 @@ func distance(from, to token.Position) int {
 
 // Sets multiLine to true if the declaration spans multiple lines.
 func (p *printer) funcDecl(d *ast.FuncDecl, multiLine *bool) {
-	p.leadComment(d.Doc)
+	p.setComment(d.Doc)
 	p.print(d.Pos(), token.FUNC, blank)
 	if recv := d.Recv; recv != nil {
 		// method: print receiver
@@ -1276,7 +1264,7 @@ func declToken(decl ast.Decl) (tok token.Token) {
 
 
 func (p *printer) file(src *ast.File) {
-	p.leadComment(src.Doc)
+	p.setComment(src.Doc)
 	p.print(src.Pos(), token.PACKAGE, blank)
 	p.expr(src.Name, ignoreMultiLine)
 
diff --git a/src/pkg/go/printer/printer.go b/src/pkg/go/printer/printer.go
index 7321c0da1f..95f0058c7f 100644
--- a/src/pkg/go/printer/printer.go
+++ b/src/pkg/go/printer/printer.go
@@ -89,8 +89,9 @@ type printer struct {
 	lastTaggedLine int // last line for which a line tag was written
 
 	// The list of all source comments, in order of appearance.
-	comments []*ast.CommentGroup // may be nil
-	cindex   int                 // current comment index
+	comments        []*ast.CommentGroup // may be nil
+	cindex          int                 // current comment index
+	useNodeComments bool                // if not set, ignore lead and line comments of nodes
 }
 
 
@@ -246,7 +247,10 @@ func (p *printer) writeTaggedItem(data []byte, tag HTMLTag) {
 // immediately following the data.
 //
 func (p *printer) writeItem(pos token.Position, data []byte, tag HTMLTag) {
-	p.pos = pos
+	if pos.IsValid() {
+		// continue with previous position if we don't have a valid pos
+		p.pos = pos
+	}
 	if debug {
 		// do not update p.pos - use write0
 		p.write0(strings.Bytes(fmt.Sprintf("[%d:%d]", pos.Line, pos.Column)))
@@ -734,14 +738,6 @@ func (p *printer) print(args ...) {
 			}
 			p.buffer = p.buffer[0 : i+1]
 			p.buffer[i] = x
-		case []byte:
-			// TODO(gri): remove this case once commentList
-			//            handles comments correctly
-			data = x
-		case string:
-			// TODO(gri): remove this case once fieldList
-			//            handles comments correctly
-			data = strings.Bytes(x)
 		case *ast.Ident:
 			if p.Styler != nil {
 				data, tag = p.Styler.Ident(x)
@@ -976,13 +972,17 @@ func (cfg *Config) Fprint(output io.Writer, node interface{}) (int, os.Error) {
 	go func() {
 		switch n := node.(type) {
 		case ast.Expr:
+			p.useNodeComments = true
 			p.expr(n, ignoreMultiLine)
 		case ast.Stmt:
+			p.useNodeComments = true
 			p.stmt(n, ignoreMultiLine)
 		case ast.Decl:
+			p.useNodeComments = true
 			p.decl(n, atTop, ignoreMultiLine)
 		case *ast.File:
 			p.comments = n.Comments
+			p.useNodeComments = n.Comments == nil
 			p.file(n)
 		default:
 			p.errors <- os.NewError(fmt.Sprintf("printer.Fprint: unsupported node type %T", n))
diff --git a/src/pkg/go/printer/testdata/comments.golden b/src/pkg/go/printer/testdata/comments.golden
index 18a407478e..2d4f434442 100644
--- a/src/pkg/go/printer/testdata/comments.golden
+++ b/src/pkg/go/printer/testdata/comments.golden
@@ -59,6 +59,15 @@ type I2 interface {
 	G(x float) float	// exported method
 }
 
+// The S3 struct; all comments except for the last one must appear in the export.
+type S3 struct {
+	// lead comment for F1
+	F1	int	// line comment for F1
+	// lead comment for F2
+	F2	int	// line comment for F2
+	f3	int	// f3 is not exported
+}
+
 // This comment group should be separated
 // with a newline from the next comment
 // group.
diff --git a/src/pkg/go/printer/testdata/comments.input b/src/pkg/go/printer/testdata/comments.input
index 8cba7e5a2c..eec88bf95b 100644
--- a/src/pkg/go/printer/testdata/comments.input
+++ b/src/pkg/go/printer/testdata/comments.input
@@ -59,6 +59,15 @@ type I2 interface {
 	G(x float) float  // exported method
 }
 
+// The S3 struct; all comments except for the last one must appear in the export.
+type S3 struct {
+	// lead comment for F1
+	F1 int // line comment for F1
+	// lead comment for F2
+	F2 int // line comment for F2
+	f3 int // f3 is not exported
+}
+
 // This comment group should be separated
 // with a newline from the next comment
 // group.
diff --git a/src/pkg/go/printer/testdata/comments.x b/src/pkg/go/printer/testdata/comments.x
index 19fa017bcf..4d7a928ae0 100644
--- a/src/pkg/go/printer/testdata/comments.x
+++ b/src/pkg/go/printer/testdata/comments.x
@@ -6,13 +6,11 @@ package main
 // The SZ struct; it is empty.
 type SZ struct{}
 
-
 // The S0 struct; no field is exported.
 type S0 struct {
 	// contains unexported fields
 }
 
-
 // The S1 struct; some fields are not exported.
 type S1 struct {
 	S0
@@ -21,24 +19,20 @@ type S1 struct {
 	// contains unexported fields
 }
 
-
 // The S2 struct; all fields are exported.
 type S2 struct {
 	S1
 	A, B, C	float	// 3 exported fields
 }
 
-
 // The IZ interface; it is empty.
 type SZ interface{}
 
-
 // The I0 interface; no method is exported.
 type I0 interface {
 	// contains unexported methods
 }
 
-
 // The I1 interface; some methods are not exported.
 type I1 interface {
 	I0
@@ -46,10 +40,18 @@ type I1 interface {
 	// contains unexported methods
 }
 
-
 // The I2 interface; all methods are exported.
 type I2 interface {
 	I0
 	F(x float) float	// exported method
 	G(x float) float	// exported method
 }
+
+// The S3 struct; all comments except for the last one must appear in the export.
+type S3 struct {
+	// lead comment for F1
+	F1	int	// line comment for F1
+	// lead comment for F2
+	F2	int	// line comment for F2
+	// contains unexported fields
+}