[Predator] Add TouchCrashedFileMetaFeature.

appengine/findit/crash/loglinear/changelist_features/touch_crashed_file_meta.py

Index: appengine/findit/crash/loglinear/changelist_features/touch_crashed_file_meta.py
diff --git a/appengine/findit/crash/loglinear/changelist_features/touch_crashed_file_meta.py b/appengine/findit/crash/loglinear/changelist_features/touch_crashed_file_meta.py
new file mode 100644
index 0000000000000000000000000000000000000000..79d0d2bafe67b4f97723538926d444eb83bbe1a4
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+++ b/appengine/findit/crash/loglinear/changelist_features/touch_crashed_file_meta.py
@@ -0,0 +1,121 @@
+# Copyright 2017 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
+import math
+
+from crash import crash_util
+from crash.changelist_classifier import GetStackInfosForFilesGroupedByDeps
+from crash.loglinear.changelist_features.min_distance import MinDistanceFeature
+from crash.loglinear.changelist_features.top_frame_index import (
+    TopFrameIndexFeature)
+from crash.loglinear.changelist_features.touch_crashed_file import (
+    TouchCrashedFileFeature)
+from crash.loglinear.feature import ChangedFile
+from crash.loglinear.feature import MetaFeature
+from crash.loglinear.feature import MetaFeatureValue
+from crash.loglinear.feature import LogLinearlyScaled
+from crash.suspect import StackInfo
+import libs.math.logarithms as lmath
+
+# N.B., this must not be infinity, else we'll start getting NaN values
+# from LinearMinDistanceFeature (and SquaredMinDistanceFeature).
+DEFAULT_MAX_LINE_DISTANCE = 50
+DEFAULT_MAX_FRAME_INDEX = 7
+
+
+class TouchCrashedFileMetaFeature(MetaFeature):
+  """MetaFeature that wrapps three ``Feature``s.
+
+  This feature returns ``MetaFeatureValue``, which wraps the ``FeatureValue``s
+  of ``MinDistanceFeature``, ``TopFrameIndexFeature`` and
+  ``TouchCrashedFileFeature``.
+  """
+  def __init__(self, get_repository,
+               max_line_distance=DEFAULT_MAX_LINE_DISTANCE,
+               max_frame_index=DEFAULT_MAX_FRAME_INDEX):
+    """
+    Args:
+      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``).
+        This factory is needed because the ``MinDistanceFeature`` in this meta
+        feature needs to get blame for files touched by suspect.
+      max_line_distance (int): An upper bound on the min_distance to
+        consider. This argument is optional and defaults to
+        ``DEFAULT_MAX_LINE_DISTANCE``.
+      max_frame_index (int): An upper bound on the minimum frame index
+        to consider. This argument is optional and defaults to
+        ``DEFAULT_MAX_FRAME_INDEX``.
+    """
+    min_distance_feature = MinDistanceFeature(get_repository, max_line_distance)
+    top_frame_index_feature = TopFrameIndexFeature(max_frame_index)
+    touch_crashed_file_feature = TouchCrashedFileFeature()
+
+    super(TouchCrashedFileMetaFeature, self).__init__({
+        min_distance_feature.name: min_distance_feature,
+        top_frame_index_feature.name: top_frame_index_feature,
+        touch_crashed_file_feature.name: touch_crashed_file_feature
+    })
+
+  @property
+  def name(self):
+    return 'TouchCrashedFileMeta'
+
+  def __call__(self, report):
+    """Returns a function mapping suspect to its ``MetaFeatureValue``.
+
+    Args:
+      report (CrashReportWithDependensies): the crash report being analyzed.
+
+    Returns:
+      A function from ``Suspect`` to ``MetaFeatureValue``, ``MetaFeatureValue``
+      wraps ``FeatureValue`` of "MinDistance" (the minimum distance between the
+      stacktrace and the suspect, as a log-domain ``float``), ``FeatureValue``
+      of "TopFrameIndex" (the top frame index of the stack frame touched by
+      the suspect, as a log-domain ``float``.) and ``FeatureValue`` of
+      "TouchCrashedFileFeature" (whether this suspect touched file or not)
+    """
+    # Preprocessing stacktrace and stack_deps to get crashed file information
+    # about the frames and callstack priority of that crashed file in
+    # stacktrace.
+    dep_to_file_to_stack_infos = GetStackInfosForFilesGroupedByDeps(
+        report.stacktrace, report.dependencies)
+    features_given_report = {name: feature(report)
+                             for name, feature in self.iteritems()}
+
+    def FeatureValueGivenReport(suspect):
+      """Function mapping suspect related data to its FeatureValue.
+
+      Args:
+        suspect (Suspect): The suspected changelog and some meta information
+          about it.
+        touched_file_to_stack_infos(dict): Dict mapping ``FileChangeInfo`` to
+          a list of ``StackInfo``s representing all the frames that the suspect
+          touched.
+
+      Returns:
+        The ``FeatureValue`` of this feature.
+      """
+      # All crashed files in stacktrace to stack-related information mapping.
+      file_to_stack_infos = dep_to_file_to_stack_infos[suspect.dep_path]
+      # Dict mapping files in stacktrace touched by suspect to there
+      # corresponding stacktrace frames information.
+      touched_file_to_stack_infos = {}
+
+      for crashed_file_path, stack_infos in file_to_stack_infos.iteritems():
+        for touched_file_info in suspect.changelog.touched_files:
+          if crash_util.IsSameFilePath(crashed_file_path,
+                                       touched_file_info.new_path):
+            touched_file_to_stack_infos[touched_file_info] = stack_infos
+
+      return MetaFeatureValue(
+          self.name, {name: fx(suspect, touched_file_to_stack_infos)
+                      for name, fx in features_given_report.iteritems()})
+
+    return FeatureValueGivenReport