vpython: Add filesystem operation / test packages.

vpython/filesystem/filesystem.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 filesystem
+
+import (
+        "os"
+        "path/filepath"
+
+        "github.com/luci/luci-go/common/errors"
+)
+
+// MakeDirs is a convenience wrapper around os.MkdirAll that applies a 0755
+// mask to all created directories.
+func MakeDirs(path string) error {
+        if err := os.MkdirAll(path, 0755); err != nil {
+                return errors.Annotate(err).Err()
+        }
+        return nil
+}
+
+// AbsPath is a convenience wrapper around filepath.Abs that accepts a string
+// pointer, base, and updates it on successful resolution.
+func AbsPath(base *string) error {
+        v, err := filepath.Abs(*base)
+        if err != nil {
+                return errors.Annotate(err).Reason("unable to resolve absolute path").

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

did you want to include 'base' in this Reason? or are you only printing full
stacks?

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

Just chaining it here. I am printing full stacks, so this will be included.

+                        D("base", *base).
+                        Err()
+        }
+        *base = v
+        return nil
+}
+
+// Touch creates a new, empty file at the specified path.
+func Touch(path string, mode os.FileMode) error {
+        fd, err := os.OpenFile(path, (os.O_CREATE | os.O_RDWR | os.O_TRUNC), mode)
+        if err != nil {
+                return errors.Annotate(err).Err()
+        }
+        return fd.Close()
+}
+
+// RemoveAll is a wrapper around os.RemoveAll which makes sure all files are
+// writeable (recursively) prior to removing them.
+func RemoveAll(path string) error {
+        if err := MakeUserWritable(path); err != nil {
+                return errors.Annotate(err).Reason("failed to mark user-writable").Err()
+        }
+        if err := os.RemoveAll(path); err != nil {

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

RemoveAll is pretty short: https://golang.org/src/os/path.go?s=1634:1667#L56

Maybe it would be worth implementing a new version of it that integrates the
chmod so that we don't have to recurse the filesystem twice (relatively
expensive on windows, lots of extra stats)

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

Done. This is probably not a huge gain, though, since only directories are
stat-ted in RemoveAll.

+                return errors.Annotate(err).Err()
+        }
+        return nil
+}
+
+// MakeReadOnly recursively iterates through all of the files and directories
+// starting at path and marks them read-only.
+func MakeReadOnly(path string, filter func(string) bool) error {
+        return recursiveChmod(path, filter, func(mode os.FileMode) os.FileMode {
+                return mode & (^os.FileMode(0222))
+        })
+}
+
+// MakeUserWritable recursively iterates through all of the files and
+// directories starting at path and ensures that they are user-writable.
+func MakeUserWritable(path string) error {
+        return recursiveChmod(path, nil, func(mode os.FileMode) os.FileMode {
+                return (mode | 0200)
+        })
+}
+
+func recursiveChmod(path string, filter func(string) bool, chmod func(mode os.FileMode) os.FileMode) error {
+        if filter == nil {
+                filter = func(string) bool { return true }
+        }
+
+        err := filepath.Walk(path, func(path string, info os.FileInfo, err error) error {
+                if err != nil {
+                        return errors.Annotate(err).Err()
+                }
+
+                mode := info.Mode()
+                if (mode.IsRegular() || mode.IsDir()) && filter(path) {
+                        if newMode := chmod(mode); newMode != mode {
+                                if err := os.Chmod(path, newMode); err != nil {
+                                        return errors.Annotate(err).Reason("failed to set read-only: %(path)s").

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

read-only? maybe this message needs tweaking

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

Done.

+                                                D("path", path).
+                                                Err()
+                                }
+                        }
+                }
+                return nil
+        })
+        if err != nil {
+                return errors.Annotate(err).Err()
+        }
+        return nil
+}