[Findit] Factoring out the components, so they can classify themselves

appengine/findit/crash/component.py

Index: appengine/findit/crash/component.py
diff --git a/appengine/findit/crash/component.py b/appengine/findit/crash/component.py
new file mode 100644
index 0000000000000000000000000000000000000000..37f1f2ce91d258e8b6ead21821fd8fd181860ed6
--- /dev/null
+++ b/appengine/findit/crash/component.py
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+# Copyright 2016 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+import collections
+import re
+
+
+# TODO(wrengr): write the coverage tests the old version was lacking.
+class Component(collections.namedtuple('Component',
+    ['component_name', 'path_regex', 'function_regex'])): # pragma: no cover
+  """A representation of a "component" in Chromium.
+
+  For example: 'Blink>DOM' or 'Blink>HTML'. Notably, a component knows
+  how to identify itself. Hence, given a stack frame or change list
+  or whatever, we ask the Component whether it matches that frame,
+  CL, etc."""
+  __slots__ = ()
+
+  def __new__(cls, component_name, path_regex, function_regex=None):
+    return super(cls, Component).__new__(cls,
+      component_name,
+      re.compile(path_regex),
+      re.compile(function_regex) if function_regex else None)
+
+
+  def MatchesStackFrame(self, frame):
+    """Return true if this component matches the frame."""
+    if not self.path_regex.match(frame.dep_path + frame.file_path):
+      return False
+
+    # We interpret function_regex=None to mean the regex that matches
+    # everything.
+    if not self.function_regex:
+      return True
+    return self.function_regex.match(frame.function)
+