go.tools/cmd/godex: fix prefix generation, filtering, formatting

Details:
- auto-generate prefixes for std lib (e.g., "godex big" works now)
- apply filtering to package-level objects only
- nicer formatting of single-entry const, var, or type declaration

TBR=adonovan
R=adonovan
CC=golang-codereviews
https://golang.org/cl/81360046

cmd/godex/godex.go

@@ -76,12 +76,11 @@ func main() {
 		}
 
 		// filter objects if needed
-		filter := types.Object.Exported
+		var filter func(types.Object) bool
 		if name != "" {
-			f := filter
 			filter = func(obj types.Object) bool {
 				// TODO(gri) perhaps use regular expression matching here?
-				return f(obj) && obj.Name() == name
+				return obj.Name() == name
 			}
 		}
 
@@ -176,7 +175,8 @@ func lookup(src string) types.Importer {
 func genPrefixes(out chan string) {
 	out <- "" // try no prefix
 	platform := build.Default.GOOS + "_" + build.Default.GOARCH
-	for _, dirname := range filepath.SplitList(build.Default.GOPATH) {
+	dirnames := append([]string{build.Default.GOROOT}, filepath.SplitList(build.Default.GOPATH)...)
+	for _, dirname := range dirnames {
 		walkDir(filepath.Join(dirname, "pkg", platform), "", out)
 	}
 	close(out)

cmd/godex/print.go

@@ -12,8 +12,8 @@ import (
 	"code.google.com/p/go.tools/go/types"
 )
 
-// TODO(gri) filter unexported fields of struct types?
 // TODO(gri) use tabwriter for alignment?
+// TODO(gri) should print intuitive method sets
 
 func print(w io.Writer, pkg *types.Package, filter func(types.Object) bool) {
 	var p printer
@@ -62,7 +62,10 @@ func (p *printer) printPackage(pkg *types.Package, filter func(types.Object) boo
 	)
 	scope := pkg.Scope()
 	for _, name := range scope.Names() {
-		if obj := scope.Lookup(name); filter(obj) {
+		obj := scope.Lookup(name)
+		if obj.Exported() {
+			// collect top-level exported and possibly filtered objects
+			if filter == nil || filter(obj) {
 				switch obj := obj.(type) {
 				case *types.Const:
 					consts = append(consts, obj)
@@ -82,8 +85,9 @@ func (p *printer) printPackage(pkg *types.Package, filter func(types.Object) boo
 					// for unsafe.Sizeof, etc.
 					builtins = append(builtins, obj)
 				}
-		} else {
-			// type is filtered out but may contain visible methods
+			}
+		} else if filter == nil {
+			// no filtering: collect top-level unexported types with methods
 			if obj, _ := obj.(*types.TypeName); obj != nil {
 				// see case *types.TypeName above
 				if named, _ := obj.Type().(*types.Named); named != nil && named.NumMethods() > 0 {
@@ -93,75 +97,88 @@ func (p *printer) printPackage(pkg *types.Package, filter func(types.Object) boo
 		}
 	}
 
-	p.printf("package %s  // %q\n\n", pkg.Name(), pkg.Path())
+	p.printf("package %s  // %q\n", pkg.Name(), pkg.Path())
 
-	if len(consts) > 0 {
-		p.print("const (\n")
-		p.indent++
+	p.printDecl("const", len(consts), func() {
 		for _, obj := range consts {
 			p.printObj(obj)
 			p.print("\n")
 		}
-		p.indent--
-		p.print(")\n\n")
-	}
+	})
 
-	if len(vars) > 0 {
-		p.print("var (\n")
-		p.indent++
+	p.printDecl("var", len(vars), func() {
 		for _, obj := range vars {
 			p.printObj(obj)
 			p.print("\n")
 		}
-		p.indent--
-		p.print(")\n\n")
-	}
+	})
 
-	if len(typez) > 0 {
-		p.print("type (\n")
-		p.indent++
+	p.printDecl("type", len(typez), func() {
 		for _, obj := range typez {
 			p.printf("%s ", obj.Name())
 			p.writeType(p.pkg, obj.Type().Underlying())
 			p.print("\n")
 		}
-		p.indent--
-		p.print(")\n\n")
-	}
+	})
 
 	for _, typ := range typem {
-		hasEntries := false
-		if obj := typ.Obj(); filter(obj) {
+		first := true
+		if obj := typ.Obj(); obj.Exported() {
+			if first {
+				p.print("\n")
+				first = false
+			}
 			p.printf("type %s ", obj.Name())
 			p.writeType(p.pkg, typ.Underlying())
 			p.print("\n")
-			hasEntries = true
 		}
 		for i, n := 0, typ.NumMethods(); i < n; i++ {
-			if obj := typ.Method(i); filter(obj) {
+			if obj := typ.Method(i); obj.Exported() {
+				if first {
+					p.print("\n")
+					first = false
+				}
 				p.printFunc(obj)
 				p.print("\n")
-				hasEntries = true
 			}
 		}
-		if hasEntries {
-			p.print("\n")
-		}
 	}
 
+	if len(funcs) > 0 {
+		p.print("\n")
 		for _, obj := range funcs {
 			p.printFunc(obj)
 			p.print("\n")
 		}
+	}
 
 	// TODO(gri) better handling of builtins (package unsafe only)
+	if len(builtins) > 0 {
+		p.print("\n")
 		for _, obj := range builtins {
 			p.printf("func %s() // builtin\n", obj.Name())
 		}
+	}
 
 	p.print("\n")
 }
 
+func (p *printer) printDecl(keyword string, n int, printGroup func()) {
+	switch n {
+	case 0:
+		// nothing to do
+	case 1:
+		p.printf("\n%s ", keyword)
+		printGroup()
+	default:
+		p.printf("\n%s (\n", keyword)
+		p.indent++
+		printGroup()
+		p.indent--
+		p.print(")\n")
+	}
+}
+
 func (p *printer) printObj(obj types.Object) {
 	p.printf("%s", obj.Name())
 	// don't write untyped types (for constants)
@@ -170,6 +187,7 @@ func (p *printer) printObj(obj types.Object) {
 		p.writeType(p.pkg, typ)
 	}
 	// write constant value
+	// TODO(gri) use floating-point notation for exact floating-point numbers (fractions)
 	if obj, ok := obj.(*types.Const); ok {
 		p.printf(" = %s", obj.Val())
 	}

cmd/godex/writetype.go

@@ -64,7 +64,6 @@ func (p *printer) writeTypeInternal(this *types.Package, typ types.Type, visited
 		p.writeTypeInternal(this, t.Elem(), visited)
 
 	case *types.Struct:
-		// TODO(gri) filter fields?
 		n := t.NumFields()
 		if n == 0 {
 			p.print("struct{}")
@@ -110,7 +109,6 @@ func (p *printer) writeTypeInternal(this *types.Package, typ types.Type, visited
 		//         m() interface{ T }
 		//     }
 		//
-		// TODO(gri) filter methods?
 		n := t.NumMethods()
 		if n == 0 {
 			p.print("interface{}")