1 files changed, 71 insertions, 0 deletions
diff --git a/src/cmd/gofix/stringssplit.go b/src/cmd/gofix/stringssplit.go
new file mode 100644
index 000000000..4a1fe93d3
--- /dev/null
+++ b/src/cmd/gofix/stringssplit.go
@@ -0,0 +1,71 @@
+// 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"
+	"go/token"
+)
+
+var stringssplitFix = fix{
+	"stringssplit",
+	stringssplit,
+	`Restore strings.Split to its original meaning and add strings.SplitN. Bytes too.
+
+http://codereview.appspot.com/4661051
+`,
+}
+
+func init() {
+	register(stringssplitFix)
+}
+
+func stringssplit(f *ast.File) bool {
+	if !imports(f, "bytes") && !imports(f, "strings") {
+		return false
+	}
+
+	fixed := false
+	walk(f, func(n interface{}) {
+		call, ok := n.(*ast.CallExpr)
+		// func Split(s, sep string, n int) []string
+		// func SplitAfter(s, sep string, n int) []string
+		if !ok || len(call.Args) != 3 {
+			return
+		}
+		// Is this our function?
+		switch {
+		case isPkgDot(call.Fun, "bytes", "Split"):
+		case isPkgDot(call.Fun, "bytes", "SplitAfter"):
+		case isPkgDot(call.Fun, "strings", "Split"):
+		case isPkgDot(call.Fun, "strings", "SplitAfter"):
+		default:
+			return
+		}
+
+		sel := call.Fun.(*ast.SelectorExpr)
+		args := call.Args
+		fixed = true // We're committed.
+
+		// Is the last argument -1? If so, drop the arg.
+		// (Actually we just look for a negative integer literal.)
+		// Otherwise, Split->SplitN and keep the arg.
+		final := args[2]
+		if unary, ok := final.(*ast.UnaryExpr); ok && unary.Op == token.SUB {
+			if lit, ok := unary.X.(*ast.BasicLit); ok {
+				// Is it an integer? If so, it's a negative integer and that's what we're after.
+				if lit.Kind == token.INT {
+					// drop the last arg.
+					call.Args = args[0:2]
+					return
+				}
+			}
+		}
+
+		// If not, rename and keep the argument list.
+		sel.Sel.Name += "N"
+	})
+	return fixed
+}