Converting various classes to namedtuples

appengine/findit/crash/changelist_classifier.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 logging
 from collections import defaultdict
+from collections import namedtuple
 
 from common import chrome_dependency_fetcher
 from crash import crash_util
 from crash.results import MatchResults
 from crash.scorers.aggregated_scorer import AggregatedScorer
 from crash.scorers.min_distance import MinDistance
 from crash.scorers.top_frame_index import TopFrameIndex
 from crash.stacktrace import CallStack
 from crash.stacktrace import Stacktrace
 from lib.gitiles.diff import ChangeType
 
-# TODO(http://crbug.com/661822): convert this into a namedtuple.
-class ChangelistClassifier(object):
-  def __init__(self, repository,
+class ChangelistClassifier(namedtuple('ChangelistClassifier',
+    ['repository', 'top_n_frames', 'top_n_results', 'confidence_threshold'])):
+  __slots__ = ()
+
+  def __new__(cls, repository,
       top_n_frames, top_n_results=3, confidence_threshold=0.999):
     """Args:
       repository (Repository): the Git repository for getting CLs to classify.
       top_n_frames (int): how many frames of each callstack to look at.
       top_n_results (int): maximum number of results to return.
       confidence_threshold (float): In [0,1], above which we only return
         the first result.
     """
-    self._repository = repository
-    self.top_n_frames = top_n_frames
-    self.top_n_results = top_n_results
-    self.confidence_threshold = confidence_threshold
+    return super(cls, ChangelistClassifier).__new__(cls,
+        repository, top_n_frames, top_n_results, confidence_threshold)
 
   def __str__(self): # pragma: no cover
     return ('%s(top_n_frames=%d, top_n_results=%d, confidence_threshold=%g)'
         % (self.__class__.__name__,
            self.top_n_frames,
            self.top_n_results,
            self.confidence_threshold))
 
   def __call__(self, report):
     """Finds changelists suspected of being responsible for the crash report.
@@ skipping 22 matching lines @@
         for stack in report.stacktrace])
 
     # We are only interested in the deps in crash stack (the callstack that
     # caused the crash).
     # TODO(wrengr): we may want to receive the crash deps as an argument,
     # so that when this method is called via Findit.FindCulprit, we avoid
     # doing redundant work creating it.
     stack_deps = GetDepsInCrashStack(
         report.stacktrace.crash_stack,
         chrome_dependency_fetcher.ChromeDependencyFetcher(
-            self._repository).GetDependency(report.crashed_version,
-                                            report.platform))
+            self.repository).GetDependency(report.crashed_version,
+                                           report.platform))
 
     # Get dep and file to changelogs, stack_info and blame dicts.
     dep_rolls = chrome_dependency_fetcher.ChromeDependencyFetcher(
-        self._repository).GetDependencyRollsDict(
+        self.repository).GetDependencyRollsDict(
             last_good_version, first_bad_version, report.platform)
 
     # Regression of a dep added/deleted (old_revision/new_revision is None) can
     # not be known for sure and this case rarely happens, so just filter them
     # out.
     regression_deps_rolls = {}
     for dep_path, dep_roll in dep_rolls.iteritems():
       if not dep_roll.old_revision or not dep_roll.new_revision:
         logging.info('Skip %s denpendency %s',
                      'added' if dep_roll.new_revision else 'deleted', dep_path)
         continue
       regression_deps_rolls[dep_path] = dep_roll
 
     dep_to_file_to_changelogs, ignore_cls = GetChangeLogsForFilesGroupedByDeps(
-        regression_deps_rolls, stack_deps, self._repository)
+        regression_deps_rolls, stack_deps, self.repository)
     dep_to_file_to_stack_infos = GetStackInfosForFilesGroupedByDeps(
         stacktrace, stack_deps)
 
     # TODO: argument order is inconsistent from others. Repository should
     # be last argument.
     results = FindMatchResults(dep_to_file_to_changelogs,
                                dep_to_file_to_stack_infos,
-                               stack_deps, self._repository, ignore_cls)
+                               stack_deps, self.repository, ignore_cls)
     if not results:
       return []
 
     # TODO(wrengr): we should be able to do this map/filter/sort in one pass.
     # Set result.confidence, result.reasons and result.changed_files.
     aggregated_scorer = AggregatedScorer([TopFrameIndex(), MinDistance()])
     map(aggregated_scorer.Score, results)
 
     # Filter all the 0 confidence results.
     results = filter(lambda r: r.confidence != 0, results)
@@ skipping 187 matching lines @@
         repository.repo_url = stack_deps[dep].repo_url
         blame = repository.GetBlame(touched_file_path,
                                     stack_deps[dep].revision)
 
         # Generate/update each result(changelog) in changelogs, blame is used
         # to calculate distance between touched lines and crashed lines in file.
         match_results.GenerateMatchResults(
             touched_file_path, dep, stack_infos, changelogs, blame)
 
   return match_results.values()