code review 4893043: url: new package

src/cmd/gofix/url.go

Index: src/cmd/gofix/url.go
===================================================================
new file mode 100644
--- /dev/null
+++ b/src/cmd/gofix/url.go
@@ -0,0 +1,116 @@
+// Copyright 2011 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 main
+
+import (
+	"fmt"
+	"os"
+	"go/ast"
+)
+
+var _ fmt.Stringer
+var _ os.Error
+
+var urlFix = fix{
+	"url",
+	url,
+	`Move the URL pieces of package http into a new package, url.
+
+http://codereview.appspot.com/4893043
+`,
+}
+
+func init() {
+	register(urlFix)
+}
+
+var urlRenames = []struct{ in, out string }{
+	{"ParseURL", "Parse"},
+	{"ParseURLReference", "ParseWithReference"},
+	{"ParseQuery", "ParseQuery"},
+	{"Values", "Values"},
+	{"URLEscape", "QueryEscape"},
+	{"URLUnescape", "QueryUnescape"},
+	{"URLError", "Error"},
+	{"URLEscapeError", "EscapeError"},
+}
+
+func url(f *ast.File) bool {
+	if imports(f, "url") || !imports(f, "http") {
+		return false
+	}
+
+	fixed := false
+
+	// Update URL code.
+	urlWalk := func(n interface{}) {
+		// Is it an identifier?
+		if ident, ok := n.(*ast.Ident); ok && ident.Name == "url" {
+			ident.Name = "url_"
+			return
+		}
+		// Find declared identifiers called url that might be confused.
+		// TODO: Why does gofix not walk the Names in a ValueSpec?
+		// TODO: Just a bug; fix later as it will have consequences.
+		if valSpec, ok := n.(*ast.ValueSpec); ok {
+			for _, ident := range valSpec.Names {
+				if ident.Name == "url" {
+					ident.Name = "url_"
+				}
+			}
+		}
+		// Parameter and result names.
+		if fn, ok := n.(*ast.FuncType); ok {
+			fixed = urlDoFields(fn.Params) || fixed
+			fixed = urlDoFields(fn.Results) || fixed
+		}
+	}
+
+	// Fix up URL code and add import, at most once.
+	fix := func() {
+		if fixed {
+			return
+		}
+		walk(f, urlWalk)
+		addImport(f, "url")
+		fixed = true
+	}
+
+	walk(f, func(n interface{}) {
+		// Rename functions and methods.
+		if expr, ok := n.(ast.Expr); ok {
+			for _, s := range urlRenames {
+				if isPkgDot(expr, "http", s.in) {
+					fix()
+					expr.(*ast.SelectorExpr).X.(*ast.Ident).Name = "url"
+					expr.(*ast.SelectorExpr).Sel.Name = s.out
+					return
+				}
+			}
+		}
+	})
+
+	// Remove the http import if no longer needed.
+	if fixed && !usesImport(f, "http") {
+		deleteImport(f, "http")
+	}
+
+	return fixed
+}
+
+func urlDoFields(list *ast.FieldList) (fixed bool) {
+	if list == nil {
+		return
+	}
+	for _, field := range list.List {
+		for _, ident := range field.Names {
+			if ident.Name == "url" {
+				fixed = true
+				ident.Name = "url_"
+			}
+		}
+	}
+	return
+}