fix: add fix for bufio, gzip, zlib NewWriterXxx changes.weekly.2012-02-14

Fixes #2979.

R=rsc, r
CC=golang-dev
https://golang.org/cl/5664046

2 files changed, 173 insertions, 0 deletions

diff --git a/src/cmd/fix/newwriter.go b/src/cmd/fix/newwriter.go
new file mode 100644
index 0000000000..4befe24fb6
--- /dev/null
+++ b/src/cmd/fix/newwriter.go
@@ -0,0 +1,90 @@
+// 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 main
+
+import (
+	"go/ast"
+)
+
+func init() {
+	register(newWriterFix)
+}
+
+var newWriterFix = fix{
+	"newWriter",
+	"2012-02-14",
+	newWriter,
+	`Adapt bufio, gzip and zlib NewWriterXxx calls for whether they return errors.
+
+Also rename gzip.Compressor and gzip.Decompressor to gzip.Writer and gzip.Reader.
+
+http://codereview.appspot.com/5639057 and
+http://codereview.appspot.com/5642054
+`,
+}
+
+func newWriter(f *ast.File) bool {
+	if !imports(f, "bufio") && !imports(f, "compress/gzip") && !imports(f, "compress/zlib") {
+		return false
+	}
+
+	fixed := false
+	walk(f, func(n interface{}) {
+		switch n := n.(type) {
+		case *ast.SelectorExpr:
+			if isTopName(n.X, "gzip") {
+				switch n.Sel.String() {
+				case "Compressor":
+					n.Sel = &ast.Ident{Name: "Writer"}
+					fixed = true
+				case "Decompressor":
+					n.Sel = &ast.Ident{Name: "Reader"}
+					fixed = true
+				}
+			} else if isTopName(n.X, "zlib") {
+				if n.Sel.String() == "NewWriterDict" {
+					n.Sel = &ast.Ident{Name: "NewWriterLevelDict"}
+					fixed = true
+				}
+			}
+
+		case *ast.AssignStmt:
+			// Drop the ", _" in assignments of the form:
+			//	w0, _ = gzip.NewWriter(w1)
+			if len(n.Lhs) != 2 || len(n.Rhs) != 1 {
+				return
+			}
+			i, ok := n.Lhs[1].(*ast.Ident)
+			if !ok {
+				return
+			}
+			if i.String() != "_" {
+				return
+			}
+			c, ok := n.Rhs[0].(*ast.CallExpr)
+			if !ok {
+				return
+			}
+			s, ok := c.Fun.(*ast.SelectorExpr)
+			if !ok {
+				return
+			}
+			sel := s.Sel.String()
+			switch {
+			case isTopName(s.X, "bufio") && (sel == "NewReaderSize" || sel == "NewWriterSize"):
+				// No-op.
+			case isTopName(s.X, "gzip") && sel == "NewWriter":
+				// No-op.
+			case isTopName(s.X, "zlib") && sel == "NewWriter":
+				// No-op.
+			default:
+				return
+			}
+			n.Lhs = n.Lhs[:1]
+			fixed = true
+		}
+	})
+	return fixed
+}
diff --git a/src/cmd/fix/newwriter_test.go b/src/cmd/fix/newwriter_test.go
new file mode 100644
index 0000000000..1f59628a0d
--- /dev/null
+++ b/src/cmd/fix/newwriter_test.go
@@ -0,0 +1,83 @@
+// 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 main
+
+func init() {
+	addTestCases(newWriterTests, newWriter)
+}
+
+var newWriterTests = []testCase{
+	{
+		Name: "newWriter.0",
+		In: `package main
+
+import (
+	"bufio"
+	"compress/gzip"
+	"compress/zlib"
+	"io"
+
+	"foo"
+)
+
+func f() *gzip.Compressor {
+	var (
+		_ gzip.Compressor
+		_ *gzip.Decompressor
+		_ struct {
+			W *gzip.Compressor
+			R gzip.Decompressor
+		}
+	)
+
+	var w io.Writer
+	br := bufio.NewReader(nil)
+	br, _ = bufio.NewReaderSize(nil, 256)
+	bw, err := bufio.NewWriterSize(w, 256) // Unfixable, as it declares an err variable.
+	bw, _ = bufio.NewWriterSize(w, 256)
+	fw, _ := foo.NewWriter(w)
+	gw, _ := gzip.NewWriter(w)
+	gw, _ = gzip.NewWriter(w)
+	zw, _ := zlib.NewWriter(w)
+	_ = zlib.NewWriterDict(zw, 0, nil)
+	return gw
+}
+`,
+		Out: `package main
+
+import (
+	"bufio"
+	"compress/gzip"
+	"compress/zlib"
+	"io"
+
+	"foo"
+)
+
+func f() *gzip.Writer {
+	var (
+		_ gzip.Writer
+		_ *gzip.Reader
+		_ struct {
+			W *gzip.Writer
+			R gzip.Reader
+		}
+	)
+
+	var w io.Writer
+	br := bufio.NewReader(nil)
+	br = bufio.NewReaderSize(nil, 256)
+	bw, err := bufio.NewWriterSize(w, 256) // Unfixable, as it declares an err variable.
+	bw = bufio.NewWriterSize(w, 256)
+	fw, _ := foo.NewWriter(w)
+	gw := gzip.NewWriter(w)
+	gw = gzip.NewWriter(w)
+	zw := zlib.NewWriter(w)
+	_ = zlib.NewWriterLevelDict(zw, 0, nil)
+	return gw
+}
+`,
+	},
+}