- ast.FilterExports: strips all non-exported nodes from an AST

- use FilterExports instead of the various predicates in printer.go and doc.go
  which simplifies a lot of code and makes it easier to deal with complex cases

R=rsc
DELTA=445  (197 added, 190 deleted, 58 changed)
OCL=31110
CL=31196

src/cmd/godoc/godoc.go

@@ -198,9 +198,13 @@ func parse(path string, mode uint) (*ast.Program, *parseErrors) {
 // Templates
 
 // Return text for an AST node.
-func nodeText(node interface{}, mode uint) []byte {
+func nodeText(node interface{}) []byte {
 	var buf bytes.Buffer;
 	tw := makeTabwriter(&buf);
+	mode := uint(0);
+	if _, isProgram := node.(*ast.Program); isProgram {
+		mode = printer.DocComments;
+	}
 	printer.Fprint(tw, node, mode);
 	tw.Flush();
 	return buf.Data();
@@ -219,9 +223,9 @@ func toText(x interface{}) []byte {
 	case String:
 		return strings.Bytes(v.String());
 	case ast.Decl:
-		return nodeText(v, printer.ExportsOnly);
+		return nodeText(v);
 	case ast.Expr:
-		return nodeText(v, printer.ExportsOnly);
+		return nodeText(v);
 	}
 	var buf bytes.Buffer;
 	fmt.Fprint(&buf, x);
@@ -331,7 +335,7 @@ func serveGoSource(c *http.Conn, name string) {
 
 	var buf bytes.Buffer;
 	fmt.Fprintln(&buf, "<pre>");
-	template.HtmlEscape(&buf, nodeText(prog, printer.DocComments));
+	template.HtmlEscape(&buf, nodeText(prog));
 	fmt.Fprintln(&buf, "</pre>");
 
 	servePage(c, name + " - Go source", buf.Data());
@@ -491,6 +495,7 @@ func (p *pakDesc) Doc() (*doc.PackageDoc, *parseErrors) {
 			r.Init(prog.Name.Value, p.importpath);
 		}
 		i++;
+		ast.FilterExports(prog);  // we only care about exports
 		r.AddProgram(prog);
 	}
 

src/cmd/gofmt/gofmt.go

@@ -7,6 +7,7 @@ package main
 import (
 	"flag";
 	"fmt";
+	"go/ast";
 	"go/parser";
 	"go/printer";
 	"io";
@@ -48,9 +49,6 @@ func parserMode() uint {
 
 func printerMode() uint {
 	mode := uint(0);
-	if *exports {
-		mode |= printer.ExportsOnly;
-	}
 	if *optcommas {
 		mode |= printer.OptCommas;
 	}
@@ -100,6 +98,9 @@ func main() {
 	}
 
 	if !*silent {
+		if *exports {
+			ast.FilterExports(prog);  // ignore result
+		}
 		w := makeTabwriter(os.Stdout);
 		printer.Fprint(w, prog, printerMode());
 		w.Flush();

src/pkg/go/ast/Makefile

@@ -2,8 +2,9 @@
 # Use of this source code is governed by a BSD-style
 # license that can be found in the LICENSE file.
 
+
 # DO NOT EDIT.  Automatically generated by gobuild.
-# gobuild -m >Makefile
+# gobuild -m ast.go filter.go >Makefile
 
 D=/go/
 
@@ -20,7 +21,7 @@ test: packages
 
 coverage: packages
 	gotest
-	6cov -g `pwd` | grep -v '_test\.go:'
+	6cov -g $$(pwd) | grep -v '_test\.go:'
 
 %.$O: %.go
 	$(GC) -I_obj $*.go
@@ -34,14 +35,21 @@ coverage: packages
 O1=\
 	ast.$O\
 
+O2=\
+	filter.$O\
+
 
-phases: a1
+phases: a1 a2
 _obj$D/ast.a: phases
 
 a1: $(O1)
 	$(AR) grc _obj$D/ast.a ast.$O
 	rm -f $(O1)
 
+a2: $(O2)
+	$(AR) grc _obj$D/ast.a filter.$O
+	rm -f $(O2)
+
 
 newpkg: clean
 	mkdir -p _obj$D
@@ -49,6 +57,7 @@ newpkg: clean
 
 $(O1): newpkg
 $(O2): a1
+$(O3): a2
 
 nuke: clean
 	rm -f $(GOROOT)/pkg/$(GOOS)_$(GOARCH)$D/ast.a

src/pkg/go/ast/filter.go

+// Copyright 2009 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/ast"
+
+
+func filterIdentList(list []*Ident) []*Ident {
+	j := 0;
+	for _, x := range list {
+		if x.IsExported() {
+			list[j] = x;
+			j++;
+		}
+	}
+	return list[0 : j];
+}
+
+
+func filterType(typ Expr)
+
+func filterFieldList(list []*Field) []*Field {
+	j := 0;
+	for _, f := range list {
+		exported := false;
+		if len(f.Names) == 0 {
+			// anonymous field
+			// TODO(gri) check if the type is exported for anonymous field
+			exported = true;
+		} else {
+			f.Names = filterIdentList(f.Names);
+			exported = len(f.Names) > 0;
+		}
+		if exported {
+			filterType(f.Type);
+			list[j] = f;
+			j++;
+		}
+	}
+	return list[0 : j];
+}
+
+
+func filterType(typ Expr) {
+	switch t := typ.(type) {
+	case *ArrayType:
+		filterType(t.Elt);
+	case *StructType:
+		t.Fields = filterFieldList(t.Fields);
+	case *FuncType:
+		t.Params = filterFieldList(t.Params);
+		t.Results = filterFieldList(t.Results);
+	case *InterfaceType:
+		t.Methods = filterFieldList(t.Methods);
+	case *MapType:
+		filterType(t.Key);
+		filterType(t.Value);
+	case *ChanType:
+		filterType(t.Value);
+	}
+}
+
+
+func filterSpec(spec Spec) bool {
+	switch s := spec.(type) {
+	case *ValueSpec:
+		s.Names = filterIdentList(s.Names);
+		if len(s.Names) > 0 {
+			filterType(s.Type);
+			return true;
+		}
+	case *TypeSpec:
+		// TODO(gri) consider stripping forward declarations
+		//           of structs, interfaces, functions, and methods
+		if s.Name.IsExported() {
+			filterType(s.Type);
+			return true;
+		}
+	}
+	return false;
+}
+
+
+func filterSpecList(list []Spec) []Spec {
+	j := 0;
+	for _, s := range list {
+		if filterSpec(s) {
+			list[j] = s;
+			j++;
+		}
+	}
+	return list[0 : j];
+}
+
+
+func filterDecl(decl Decl) bool {
+	switch d := decl.(type) {
+	case *GenDecl:
+		d.Specs = filterSpecList(d.Specs);
+		return len(d.Specs) > 0;
+	case *FuncDecl:
+		// TODO consider removing function declaration altogether if
+		//      forward declaration (i.e., if d.Body == nil) because
+		//      in that case the actual declaration will come later.
+		d.Body = nil;  // strip body
+		return d.Name.IsExported();
+	}
+	return false;
+}
+
+
+// FilterExports trims an AST in place such that only exported nodes remain:
+// all top-level identififiers which are not exported and their associated
+// information (such as type, initial value, or function body) are removed.
+// Non-exported fields and methods of exported types are stripped, and the
+// function bodies of exported functions are set to nil.
+//
+// FilterExports returns true if there is an exported declaration; it returns
+// false otherwise.
+//
+func FilterExports(prog *Program) bool {
+	j := 0;
+	for _, d := range prog.Decls {
+		if filterDecl(d) {
+			prog.Decls[j] = d;
+			j++;
+		}
+	}
+	prog.Decls = prog.Decls[0 : j];
+	prog.Comments = nil;  // remove unassociated comments
+	return j > 0;
+}

src/pkg/go/doc/doc.go

@@ -17,28 +17,6 @@ import (
 )
 
 
-// ----------------------------------------------------------------------------
-// Elementary support
-
-func hasExportedNames(names []*ast.Ident) bool {
-	for i, name := range names {
-		if name.IsExported() {
-			return true;
-		}
-	}
-	return false;
-}
-
-
-func hasExportedSpecs(specs []ast.Spec) bool {
-	for i, s := range specs {
-		// only called for []astSpec lists of *ast.ValueSpec
-		return hasExportedNames(s.(*ast.ValueSpec).Names);
-	}
-	return false;
-}
-
-
 // ----------------------------------------------------------------------------
 
 type typeDoc struct {
@@ -149,33 +127,25 @@ func (doc *DocReader) addDecl(decl ast.Decl) {
 				// ignore
 			case token.CONST:
 				// constants are always handled as a group
-				if hasExportedSpecs(d.Specs) {
-					doc.consts.Push(d);
-				}
+				doc.consts.Push(d);
 			case token.TYPE:
 				// types are handled individually
+				var noPos token.Position;
 				for i, spec := range d.Specs {
+					// make a (fake) GenDecl node for this TypeSpec
+					// (we need to do this here - as opposed to just
+					// for printing - so we don't lose the GenDecl
+					// documentation)
 					s := spec.(*ast.TypeSpec);
-					if s.Name.IsExported() {
-						// make a (fake) GenDecl node for this TypeSpec
-						// (we need to do this here - as opposed to just
-						// for printing - so we don't loose the GenDecl
-						// documentation)
-						var noPos token.Position;
-						doc.addType(&ast.GenDecl{d.Doc, d.Pos(), token.TYPE, noPos, []ast.Spec{s}, noPos});
-					}
+					doc.addType(&ast.GenDecl{d.Doc, d.Pos(), token.TYPE, noPos, []ast.Spec{s}, noPos});
 				}
 			case token.VAR:
 				// variables are always handled as a group
-				if hasExportedSpecs(d.Specs) {
-					doc.vars.Push(d);
-				}
+				doc.vars.Push(d);
 			}
 		}
 	case *ast.FuncDecl:
-		if d.Name.IsExported() {
-			doc.addFunc(d);
-		}
+		doc.addFunc(d);
 	}
 }
 
@@ -194,7 +164,7 @@ func (doc *DocReader) AddProgram(prog *ast.Program) {
 		doc.doc = prog.Doc
 	}
 
-	// add all exported declarations
+	// add all declarations
 	for i, decl := range prog.Decls {
 		doc.addDecl(decl);
 	}

src/pkg/go/printer/printer.go

@@ -20,8 +20,7 @@ import (
 // to Fprint via the mode parameter.
 //
 const (
-	ExportsOnly uint = 1 << iota;  // print exported code only
-	DocComments;  // print documentation comments
+	DocComments uint = 1 << iota;  // print documentation comments
 	OptCommas;  // print optional commas
 	OptSemis;  // print optional semicolons
 )
@@ -181,97 +180,13 @@ func (p *printer) print(args ...) {
 
 
 // ----------------------------------------------------------------------------
-// Predicates
+// Printing of common AST nodes.
 
 func (p *printer) optSemis() bool {
 	return p.mode & OptSemis != 0;
 }
 
 
-func (p *printer) exportsOnly() bool {
-	return p.mode & ExportsOnly != 0;
-}
-
-
-// The isVisibleX predicates return true if X should produce any output
-// given the printing mode and depending on whether X contains exported
-// names.
-
-func (p *printer) isVisibleIdent(x *ast.Ident) bool {
-	// identifiers in local scopes (p.level > 0) are always visible
-	// if the surrounding code is printed in the first place
-	return !p.exportsOnly() || x.IsExported() || p.level > 0;
-}
-
-
-func (p *printer) isVisibleIdentList(list []*ast.Ident) bool {
-	for _, x := range list {
-		if p.isVisibleIdent(x) {
-			return true;
-		}
-	}
-	return false;
-}
-
-
-func (p *printer) isVisibleFieldList(list []*ast.Field) bool {
-	for _, f := range list {
-		if len(f.Names) == 0 {
-			// anonymous field
-			// TODO should only return true if the anonymous field
-			//      type is visible (for now be conservative and
-			//      print it so that the generated code is valid)
-			return true;
-		}
-		if p.isVisibleIdentList(f.Names) {
-			return true;
-		}
-	}
-	return false;
-}
-
-
-func (p *printer) isVisibleSpec(spec ast.Spec) bool {
-	switch s := spec.(type) {
-	case *ast.ImportSpec:
-		return !p.exportsOnly();
-	case *ast.ValueSpec:
-		return p.isVisibleIdentList(s.Names);
-	case *ast.TypeSpec:
-		return p.isVisibleIdent(s.Name);
-	}
-	panic("unreachable");
-	return false;
-}
-
-
-func (p *printer) isVisibleSpecList(list []ast.Spec) bool {
-	for _, s := range list {
-		if p.isVisibleSpec(s) {
-			return true;
-		}
-	}
-	return false;
-}
-
-
-func (p *printer) isVisibleDecl(decl ast.Decl) bool {
-	switch d := decl.(type) {
-	case *ast.BadDecl:
-		return false;
-	case *ast.GenDecl:
-		return p.isVisibleSpecList(d.Specs);
-	case *ast.FuncDecl:
-		return p.isVisibleIdent(d.Name);
-	}
-	panic("unreachable");
-	return false;
-}
-
-
-// ----------------------------------------------------------------------------
-// Printing of common AST nodes.
-
 func (p *printer) comment(c *ast.Comment) {
 	if c != nil {
 		text := c.Text;
@@ -297,15 +212,11 @@ func (p *printer) doc(d ast.Comments) {
 func (p *printer) expr(x ast.Expr) bool
 
 func (p *printer) identList(list []*ast.Ident) {
-	needsComma := false;
 	for i, x := range list {
-		if p.isVisibleIdent(x) {
-			if needsComma {
-				p.print(token.COMMA, blank);
-			}
-			p.expr(x);
-			needsComma = true;
+		if i > 0 {
+			p.print(token.COMMA, blank);
 		}
+		p.expr(x);
 	}
 }
 
@@ -362,83 +273,73 @@ func (p *printer) signature(params, result []*ast.Field) {
 
 // Returns true if the field list ends in a closing brace.
 func (p *printer) fieldList(lbrace token.Position, list []*ast.Field, rbrace token.Position, isInterface bool) bool {
-	hasBody := p.isVisibleFieldList(list);
-	if !lbrace.IsValid() || p.exportsOnly() && !hasBody {
-		// forward declaration without {}'s or no visible exported fields
-		// (in all other cases, the {}'s must be printed even if there are
-		// no fields, otherwise the type is incorrect)
+	if !lbrace.IsValid() {
+		// forward declaration without {}'s
 		return false;  // no {}'s
 	}
 
-	p.print(blank, lbrace, token.LBRACE);
+	if len(list) == 0 {
+		p.print(blank, lbrace, token.LBRACE, rbrace, token.RBRACE);
+		return true;  // empty list with {}'s
+	}
 
-	if hasBody {
-		p.print(+1, newline);
+	p.print(blank, lbrace, token.LBRACE, +1, newline);
 
-		var needsSemi bool;
-		var lastWasAnon bool;  // true if the previous line was an anonymous field
-		var lastComment *ast.Comment;  // the comment from the previous line
-		for _, f := range list {
-			hasNames := p.isVisibleIdentList(f.Names);
-			isAnon := len(f.Names) == 0;
-
-			if hasNames || isAnon {
-				// at least one visible identifier or anonymous field
-				// TODO this is conservative - see isVisibleFieldList
-				if needsSemi {
-					p.print(token.SEMICOLON);
-					p.comment(lastComment);
-					if lastWasAnon == isAnon {
-						// previous and current line have same structure;
-						// continue with existing columns
-						p.print(newline);
-					} else {
-						// previous and current line have different structure;
-						// flush tabwriter and start new columns (the "type
-						// column" on a line with named fields may line up
-						// with the "trailing comment column" on a line with
-						// an anonymous field, leading to bad alignment)
-						p.print(formfeed);
-					}
-				}
-
-				p.doc(f.Doc);
-				if hasNames {
-					p.identList(f.Names);
-					p.print(tab);
-				}
+	var lastWasAnon bool;  // true if the previous line was an anonymous field
+	var lastComment *ast.Comment;  // the comment from the previous line
+	for i, f := range list {
+		// at least one visible identifier or anonymous field
+		isAnon := len(f.Names) == 0;
+		if i > 0 {
+			p.print(token.SEMICOLON);
+			p.comment(lastComment);
+			if lastWasAnon == isAnon {
+				// previous and current line have same structure;
+				// continue with existing columns
+				p.print(newline);
+			} else {
+				// previous and current line have different structure;
+				// flush tabwriter and start new columns (the "type
+				// column" on a line with named fields may line up
+				// with the "trailing comment column" on a line with
+				// an anonymous field, leading to bad alignment)
+				p.print(formfeed);
+			}
+		}
 
-				if isInterface {
-					if ftyp, isFtyp := f.Type.(*ast.FuncType); isFtyp {
-						// methods
-						p.signature(ftyp.Params, ftyp.Results);
-					} else {
-						// embedded interface
-						p.expr(f.Type);
-					}
-				} else {
-					p.expr(f.Type);
-					if f.Tag != nil && !p.exportsOnly() {
-						p.print(tab);
-						p.expr(&ast.StringList{f.Tag});
-					}
-				}
+		p.doc(f.Doc);
+		if !isAnon {
+			p.identList(f.Names);
+			p.print(tab);
+		}
 
-				needsSemi = true;
-				lastWasAnon = isAnon;
-				lastComment = f.Comment;
+		if isInterface {
+			if ftyp, isFtyp := f.Type.(*ast.FuncType); isFtyp {
+				// methods
+				p.signature(ftyp.Params, ftyp.Results);
+			} else {
+				// embedded interface
+				p.expr(f.Type);
+			}
+		} else {
+			p.expr(f.Type);
+			if f.Tag != nil {
+				p.print(tab);
+				p.expr(&ast.StringList{f.Tag});
 			}
 		}
 
-		if p.optSemis() {
-			p.print(token.SEMICOLON);
-		}
+		lastWasAnon = isAnon;
+		lastComment = f.Comment;
+	}
 
-		p.comment(lastComment);
-		p.print(-1, newline);
+	if p.optSemis() {
+		p.print(token.SEMICOLON);
 	}
+	p.comment(lastComment);
+
+	p.print(-1, newline, rbrace, token.RBRACE);
 
-	p.print(rbrace, token.RBRACE);
 	return true;  // field list with {}'s
 }
 
@@ -905,25 +806,17 @@ func (p *printer) decl(decl ast.Decl) (optSemi bool) {
 
 		if d.Lparen.IsValid() {
 			// group of parenthesized declarations
-			p.print(d.Lparen, token.LPAREN);
-			if p.isVisibleSpecList(d.Specs) {
-				p.print(+1, newline);
-				semi := false;
-				for _, s := range d.Specs {
-					if p.isVisibleSpec(s) {
-						if semi {
-							p.print(token.SEMICOLON, newline);
-						}
-						p.spec(s);
-						semi = true;
-					}
-				}
-				if p.optSemis() {
-					p.print(token.SEMICOLON);
+			p.print(d.Lparen, token.LPAREN, +1, newline);
+			for i, s := range d.Specs {
+				if i > 0 {
+					p.print(token.SEMICOLON, newline);
 				}
-				p.print(-1, newline);
+				p.spec(s);
 			}
-			p.print(d.Rparen, token.RPAREN);
+			if p.optSemis() {
+				p.print(token.SEMICOLON);
+			}
+			p.print(-1, newline, d.Rparen, token.RPAREN);
 			optSemi = true;
 
 		} else {
@@ -946,7 +839,7 @@ func (p *printer) decl(decl ast.Decl) (optSemi bool) {
 		}
 		p.expr(d.Name);
 		p.signature(d.Type.Params, d.Type.Results);
-		if !p.exportsOnly() && d.Body != nil {
+		if d.Body != nil {
 			p.print(blank);
 			p.level++;  // adjust nesting level for function body
 			p.stmt(d.Body);
@@ -965,23 +858,19 @@ func (p *printer) decl(decl ast.Decl) (optSemi bool) {
 // Programs
 
 func (p *printer) program(prog *ast.Program) {
-	// set unassociated comments if all code is printed
-	if !p.exportsOnly() {
-		// TODO enable this once comments are properly interspersed
-		//p.setComments(prog.Comments);
-	}
+	// set unassociated comments
+	// TODO enable this once comments are properly interspersed
+	// p.setComments(prog.Comments);
 
 	p.doc(prog.Doc);
 	p.print(prog.Pos(), token.PACKAGE, blank);
 	p.expr(prog.Name);
 
 	for _, d := range prog.Decls {
-		if p.isVisibleDecl(d) {
-			p.print(newline, newline);
-			p.decl(d);
-			if p.optSemis() {
-				p.print(token.SEMICOLON);
-			}
+		p.print(newline, newline);
+		p.decl(d);
+		if p.optSemis() {
+			p.print(token.SEMICOLON);
 		}
 	}