Removing the mutation in the factories for getting dep repositories

appengine/findit/crash/findit.py

 # 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 copy
 import json
 import logging
 
 from google.appengine.ext import ndb
 
 from common import appengine_util
-from common import chrome_dependency_fetcher
+from common.chrome_dependency_fetcher import ChromeDependencyFetcher
 from common import constants
 from crash.crash_report import CrashReport
 from libs import time_util
 from model import analysis_status
 from model.crash.crash_config import CrashConfig
 
 
 # TODO(http://crbug.com/659346): since most of our unit tests are
 # FinditForFracas-specific, wrengr moved them to findit_for_chromecrash_test.py.
 # However, now we're missing coverage for most of this file (due to the
 # buggy way coverage is computed). Need to add a bunch of new unittests
 # to get coverage back up.
 
 # TODO: this class depends on ndb stuff, and should therefore move to
 # cr-culprit-finder/service/predator as part of the big reorganization.
 # This class should be renamed to avoid confustion between Findit and Predator.
 # Think of a good name (e.g.'PredatorApp') for this class.
 class Findit(object):
-  def __init__(self, repository):
+  def __init__(self, get_repository):
     """
     Args:
-      repository (Repository): the Git repository for getting CLs to classify.
+      get_repository (callable): a function from DEP urls to ``Repository``
+        objects, so we can get changelogs and blame for each dep. Notably,
+        to keep the code here generic, we make no assumptions about
+        which subclass of ``Repository`` this function returns. Thus,
+        it is up to the caller to decide what class to return and handle
+        any other arguments that class may require (e.g., an http client
+        for ``GitilesRepository``).
     """
-    self._repository = repository
+    self._get_repository = get_repository
+    self._dep_fetcher = ChromeDependencyFetcher(get_repository)
     # TODO(http://crbug.com/659354): because self.client is volatile,
-    # we need some way of updating the Azelea instance whenever the
+    # we need some way of updating the Predator instance whenever the
     # config changes. How to do that cleanly?
     self._predator = None
     self._stacktrace_parser = None
 
   # This is a class method because it should be the same for all
   # instances of this class. We can in fact call class methods on
   # instances (not just on the class itself), so we could in principle
   # get by with just this method. However, a @classmethod is treated
   # syntactically like a method, thus we'd need to have the ``()`` at the
   # end, unlike for a @property. Thus we have both the class method and
@@ skipping 153 matching lines @@
     Args:
       model (CrashAnalysis): The model containing the stack_trace string
         to be parsed.
 
     Returns:
       On success, returns a Stacktrace object; on failure, returns None.
     """
     # Use up-to-date ``top_n`` in self.config to filter top n frames.
     stacktrace = self._stacktrace_parser.Parse(
         model.stack_trace,
-        chrome_dependency_fetcher.ChromeDependencyFetcher(
-            self._repository).GetDependency(
-                model.crashed_version,
-                model.platform),
-        model.signature, self.config.get('top_n'))
+        self._dep_fetcher.GetDependency(model.crashed_version, model.platform),
+        model.signature,
+        self.config.get('top_n'))
     if not stacktrace:
       logging.warning('Failed to parse the stacktrace %s', model.stack_trace)
       return None
 
     return stacktrace
 
   def ProcessResultForPublishing(self, result, key):
     """Client specific processing of result data for publishing."""
     raise NotImplementedError()
 
@@ skipping 39 matching lines @@
     stacktrace = self.ParseStacktrace(model)
     if stacktrace is None:
       return None
 
     return self._predator.FindCulprit(CrashReport(
         crashed_version = model.crashed_version,
         signature = model.signature,
         platform = model.platform,
         stacktrace = stacktrace,
         regression_range = model.regression_range))