Interface update, per-method Contexts.

service/info/support/namespace.go

+// Copyright 2015 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 support provides Info-related support functionality. It is designed
+// to be used by implementing packages.
+package support
+
+import (
+        "fmt"
+        "regexp"
+)
+
+// validNamespace matches valid namespace names.
+var validNamespace = regexp.MustCompile(`^[0-9A-Za-z._-]{0,100}$`)

[dnj, 2016/09/01 15:25:40]

Added this package b/c both impl/memory and impl/cloud like to validate
namespace, but this doesn't seem appropriate to pollute the top-level package
with.

[iannucci, 2016/09/16 01:01:14]

maybe it should move to service/datastore?

[dnj, 2016/09/16 05:44:43]

I think namespace is a concept owned by "info" service, so it makes sense to
keep it here. Also this is sort of internal-ish without being named "internal",
same role though. I don't mind leaving it here.

+
+// ValidNamespace will return an error if the supplied string is not a valid
+// namespace.
+func ValidNamespace(ns string) error {
+        if validNamespace.MatchString(ns) {
+                return nil
+        }
+        return fmt.Errorf("appengine: namespace %q does not match /%s/", ns, validNamespace)
+}