1 files changed, 124 insertions, 0 deletions
diff --git a/src/cmd/fix/osopen.go b/src/cmd/fix/osopen.go
new file mode 100644
index 000000000..af2796ac2
--- /dev/null
+++ b/src/cmd/fix/osopen.go
@@ -0,0 +1,124 @@
+// 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 (
+	"go/ast"
+)
+
+func init() {
+	register(osopenFix)
+}
+
+var osopenFix = fix{
+	"osopen",
+	"2011-04-04",
+	osopen,
+	`Adapt os.Open calls to new, easier API and rename O_CREAT O_CREATE.
+
+http://codereview.appspot.com/4357052
+`,
+}
+
+func osopen(f *ast.File) bool {
+	if !imports(f, "os") {
+		return false
+	}
+
+	fixed := false
+	walk(f, func(n interface{}) {
+		// Rename O_CREAT to O_CREATE.
+		if expr, ok := n.(ast.Expr); ok && isPkgDot(expr, "os", "O_CREAT") {
+			expr.(*ast.SelectorExpr).Sel.Name = "O_CREATE"
+			fixed = true
+			return
+		}
+
+		// Fix up calls to Open.
+		call, ok := n.(*ast.CallExpr)
+		if !ok || len(call.Args) != 3 {
+			return
+		}
+		if !isPkgDot(call.Fun, "os", "Open") {
+			return
+		}
+		sel := call.Fun.(*ast.SelectorExpr)
+		args := call.Args
+		// os.Open(a, os.O_RDONLY, c) -> os.Open(a)
+		if isPkgDot(args[1], "os", "O_RDONLY") || isPkgDot(args[1], "syscall", "O_RDONLY") {
+			call.Args = call.Args[0:1]
+			fixed = true
+			return
+		}
+		// os.Open(a, createlike_flags, c) -> os.Create(a, c)
+		if isCreateFlag(args[1]) {
+			sel.Sel.Name = "Create"
+			if !isSimplePerm(args[2]) {
+				warn(sel.Pos(), "rewrote os.Open to os.Create with permission not 0666")
+			}
+			call.Args = args[0:1]
+			fixed = true
+			return
+		}
+		// Fallback: os.Open(a, b, c) -> os.OpenFile(a, b, c)
+		sel.Sel.Name = "OpenFile"
+		fixed = true
+	})
+	return fixed
+}
+
+func isCreateFlag(flag ast.Expr) bool {
+	foundCreate := false
+	foundTrunc := false
+	// OR'ing of flags: is O_CREATE on?  + or | would be fine; we just look for os.O_CREATE
+	// and don't worry about the actual operator.
+	p := flag.Pos()
+	for {
+		lhs := flag
+		expr, isBinary := flag.(*ast.BinaryExpr)
+		if isBinary {
+			lhs = expr.Y
+		}
+		sel, ok := lhs.(*ast.SelectorExpr)
+		if !ok || !isTopName(sel.X, "os") {
+			return false
+		}
+		switch sel.Sel.Name {
+		case "O_CREATE":
+			foundCreate = true
+		case "O_TRUNC":
+			foundTrunc = true
+		case "O_RDONLY", "O_WRONLY", "O_RDWR":
+			// okay 
+		default:
+			// Unexpected flag, like O_APPEND or O_EXCL.
+			// Be conservative and do not rewrite.
+			return false
+		}
+		if !isBinary {
+			break
+		}
+		flag = expr.X
+	}
+	if !foundCreate {
+		return false
+	}
+	if !foundTrunc {
+		warn(p, "rewrote os.Open with O_CREATE but not O_TRUNC to os.Create")
+	}
+	return foundCreate
+}
+
+func isSimplePerm(perm ast.Expr) bool {
+	basicLit, ok := perm.(*ast.BasicLit)
+	if !ok {
+		return false
+	}
+	switch basicLit.Value {
+	case "0666":
+		return true
+	}
+	return false
+}