vpython: Add filesystem operation / test packages.

vpython/filesystem/testfs/build.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"
+        "path/filepath"
+        "sort"
+        "strings"
+
+        "github.com/luci/luci-go/vpython/filesystem"
+)
+
+// Build constructs a filesystem hierarchy given a layout.
+//
+// The layouts keys should be ToSlash-style file paths. Its values should be the
+// content that is written at those paths. Intermediate directories will be
+// automatically created.
+//
+// To create a directory, end its path with a "/". In this case, the content
+// will be ignored.
+func Build(base string, layout map[string]string) error {
+        keys := make([]string, 0, len(layout))
+        for k := range layout {
+                keys = append(keys, k)
+        }
+        sort.Strings(keys)
+
+        for _, path := range keys {
+                makeDir := strings.HasSuffix(path, "/")
+                content := layout[path]
+
+                // Normalize "path" to the current OS.
+                path = filepath.Join(base, filepath.FromSlash(path))
+
+                if makeDir {
+                        // Make a directory.
+                        if err := filesystem.MakeDirs(path); err != nil {
+                                return err
+                        }
+                } else {
+                        // Make a file.
+
+                        if err := filesystem.MakeDirs(filepath.Dir(path)); err != nil {
+                                return err
+                        }
+                        if err := ioutil.WriteFile(path, []byte(content), 0644); err != nil {
+                                return err
+                        }
+                }
+        }
+        return nil
+}