Add CIPD pin reporting to swarming.

appengine/swarming/cipd.py

Index: appengine/swarming/cipd.py
diff --git a/appengine/swarming/cipd.py b/appengine/swarming/cipd.py
index d04a087800194dca5f81e7745c39a40cc395ec40..ba0cdd434fdee99a0ff0c178d0a26f3a5ce1c482 100644
--- a/appengine/swarming/cipd.py
+++ b/appengine/swarming/cipd.py
@@ -33,6 +33,78 @@ PARAM_OS_VER = '${os_ver}'
 ALL_PARAMS = (PARAM_PLATFORM, PARAM_OS_VER)
 
 
+class PinChecker(object):
+  PARAM_PLATFORM_ESC = re.escape(PARAM_PLATFORM)
+  PARAM_OS_VER_ESC = re.escape(PARAM_OS_VER)
+
+  def __init__(self):
+    self.platform = None
+    self.os_ver = None
+
+  def check(self, original, expanded):

[M-A Ruel, 2016/08/30 02:18:07]

optional nit: I think I'd prefer if this function returned a new instance of
PinChecker instead of mutating.

[iannucci, 2016/08/30 09:13:29]

Done.

edit: Actually I changed it to a contextmanager. I tried the 'return an new
instance' thing, but it was super-awkward. I think the new version represents
the semantics correctly; doing checks within some lexical context where all
template parameters must be consistent.

+    """Raises ValueError if expanded is not pluasibly a pinned version of

[M-A Ruel, 2016/08/30 02:18:07]

plausibly

[iannucci, 2016/08/30 09:13:29]

Done.

+    original.
+
+    Args:
+      original - a CipdPackage which may contain templates like ${platform}
+      expanded - a CipdPackage which is nominally an expansion of original.
+
+    CipdPackage is duck-typed to have three string properties 'package_name',
+    'path' and 'version'.
+
+    Side effects:
+      If this PinChecker has not encountered a platform or os_ver value yet,
+      the appropriate property will be set on this PinChecker. Subsequent
+      executions of check will replace ${platform} with the previously-scanned
+      value.
+
+    Raises:
+      ValueError if expanded is not a valid derivation of original.
+    """
+    if original.path != expanded.path:
+      raise ValueError('Mismatched path')
+
+    def sub_param(regex, param_esc, param_re, param_const):
+      # The 1 allows each substitution to only show up in the pattern once.
+      # If it shows up more than once, then this is a very strange package name,
+      # and should be subject to further scrutiny. If it turns out that for some
+      # reason the substitutions SHOULD be allowed more than once per name, we
+      # will need to assert that the matched-values of them are also all the
+      # same (e.g. ${platform} cannot resolve to more than one value)
+      ret = False
+      if param_const is None:
+        ret = param_esc in regex
+        if ret:
+          regex = regex.replace(param_esc, param_re, 1)
+      else:
+        regex = regex.replace(param_esc, param_const, 1)
+      return regex, ret
+
+    name_regex = re.escape(original.package_name)
+    name_regex, scan_plat = sub_param(
+        name_regex, self.PARAM_PLATFORM_ESC, '(?P<platform>\w+-[a-z0-9]+)',

[M-A Ruel, 2016/08/30 02:18:07]

Use r'' otherwise your \ may not do what you think it'll do.

[iannucci, 2016/08/30 09:13:29]

Done

+        self.platform)
+    name_regex, scan_os_ver = sub_param(
+        name_regex, self.PARAM_OS_VER_ESC, '(?P<os_ver>[_a-z0-9]+)',

[M-A Ruel, 2016/08/30 02:18:07]

r'' as per habit.

[iannucci, 2016/08/30 09:13:29]

Done

+        self.os_ver)
+
+    match = re.match(name_regex, expanded.package_name)
+    if not match:
+      raise ValueError('Mismatched package_name')
+
+    if is_pinned_version(original.version):
+      if original.version != expanded.version:
+        raise ValueError('Mismatched pins')
+    else:
+      if not is_pinned_version(expanded.version):
+        raise ValueError('Pin value is not a pin')
+
+    if scan_plat:
+      self.platform = re.escape(match.group('platform'))
+    if scan_os_ver:
+      self.os_ver = re.escape(match.group('os_ver'))
+
+
 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))