swarming: add support for cipd on the server side

appengine/swarming/cipd.py

Index: appengine/swarming/cipd.py
diff --git a/appengine/swarming/cipd.py b/appengine/swarming/cipd.py
new file mode 100644
index 0000000000000000000000000000000000000000..3f33067ccbffbfa03d9f21b4ed9ef90de19e9ccf
--- /dev/null
+++ b/appengine/swarming/cipd.py
@@ -0,0 +1,43 @@
+# Copyright 2016 The LUCI Authors. All rights reserved.
+# Use of this source code is governed by the Apache v2.0 license that can be
+# found in the LICENSE file.
+
+"""CIPD-specific code is concentrated here."""
+
+import re
+
+# Regular expressions below are copied from
+# https://chromium.googlesource.com/infra/infra/+/468bb43/appengine/chrome_infra_packages/cipd/impl.py

[Paweł Hajdan Jr., 2016/04/26 08:45:22]

How about a TODO to move chrome_infra_packages to luci-py and share the regexes?

Duplicating things is a smell, and they can get out of sync.

Another idea might be to rely on CIPD itself to do the validation. I'm not sure
if we need to duplicate that here.

Just my 2c, not blocking this CL and totally up to you. With the high quality
standards for LUCI though, I thought it'd fit. Does that make sense? :)

[nodir, 2016/04/29 22:28:08]

I talked to Vadim, he is not planning to move chrome_infra_packages in the near
future and he is fine copying these 20 lines of code

+# https://chromium.googlesource.com/infra/infra/+/468bb43/appengine/chrome_infra_packages/cas/impl.py
+
+PACKAGE_NAME_RE = re.compile(r'^([a-z0-9_\-]+/)*[a-z0-9_\-]+$')
+INSTANCE_ID_RE = re.compile(r'^[0-9a-f]{40}$')
+TAG_KEY_RE = re.compile(r'^[a-z0-9_\-]$')
+REF_RE = re.compile(r'^[a-z0-9_\-]{1,100}$')
+TAG_MAX_LEN = 400
+
+
+def is_valid_package_name(package_name):
+  """Returns True if |package_name| is a valid CIPD package name."""
+  return bool(PACKAGE_NAME_RE.match(package_name))
+
+
+def is_valid_version(version):
+  """Returns True if |version| is a valid CIPD package version."""
+  return bool(
+      INSTANCE_ID_RE.match(version) or
+      is_valid_tag(version) or
+      REF_RE.match(version)
+  )
+
+def is_valid_tag(tag):
+  """True if string looks like a valid package instance tag."""
+  if not tag or ':' not in tag or len(tag) > TAG_MAX_LEN:
+    return False
+  # Care only about the key. Value can be anything (including empty string).
+  return bool(TAG_KEY_RE.match(tag.split(':', 1)[0]))
+
+
+def is_pinned_version(version):
+  """Returns True if |version| is pinned."""
+  return bool(INSTANCE_ID_RE.match(version) or TAG_KEY_RE.match(version))