vpython: Add filesystem operation / test packages.

vpython/filesystem/testfs/tempdir.go

+// Copyright 2017 The LUCI Authors. All rights reserved.
+// Use of this source code is governed under the Apache License, Version 2.0
+// that can be found in the LICENSE file.
+
+package testfs
+
+import (
+        "io/ioutil"
+
+        "github.com/luci/luci-go/vpython/filesystem"
+)
+
+// WithTempDir creates a temporary directory and passes it to fn. After fn
+// exits, the directory is cleaned up.
+func WithTempDir(prefix string, fn func(string) error) error {
+        tdir, err := ioutil.TempDir("", prefix)
+        if err != nil {
+                return err
+        }
+        defer func() {
+                _ = filesystem.RemoveAll(tdir)

[iannucci, 2017/02/21 08:25:09]

worth logging?

[dnj, 2017/02/21 18:07:49]

Done.

+        }()
+        return fn(tdir)
+}
+
+// MustWithTempDir calls WithTempDir and panics if any failures occur.
+func MustWithTempDir(prefix string, fn func(string)) func() {
+        return func() {
+                err := WithTempDir(prefix, func(tdir string) error {
+                        fn(tdir)
+                        return nil
+                })
+                if err != nil {
+                        panic(err)
+                }
+        }
+}