[Findit] Plain objects to represent the returned result from running the algorithm,

tools/findit/blame.py

+# Copyright (c) 2014 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.
+
+from threading import Lock, Thread
+
+import crash_utils
+import utils
+
+
+class Blame(object):
+  """Represents a blame object.
+
+  The object contains blame information for one line of stack, and this
+  information is shown when there are no CLs that change the crashing files.
+  Attributes:
+    content: The content of the line to find the blame for.

[aarya, 2014/08/14 20:22:20]

s/content/line_content

[jeun, 2014/08/14 22:16:48]

Done.

+    component_name: The name of the component this line is in.

[aarya, 2014/08/14 21:14:39]

s/this line is in/for this line.

[jeun, 2014/08/14 22:16:48]

Done.

+    stack_frame_index: The stack frame index of this file.
+    file_name: The name of the file.
+    line_number: The line that caused a crash.
+    author: The author of this line on the latest revision.
+    crash_revision: The revision that caused the crash.
+    revision: The latest revision of this line before the crash revision.
+    url: The url of the change for the revision.
+    range_start: The starting range of the regression for this component.
+    range_end: The ending range of the regression.
+
+  """
+
+  def __init__(self, content, component_name, stack_frame_index, file_name,
+               line_number, author, crash_revision, revision, url,
+               range_start, range_end):
+    # Set all the variables from the arguments.
+    self.content = content
+    self.component_name = component_name
+    self.stack_frame_index = stack_frame_index
+    self.file = file_name
+    self.line_number = line_number
+    self.author = author
+    self.revision = revision
+    self.url = url
+    self.distance = crash_utils.INFINITY
+    self.range_start = range_start
+    self.range_end = range_end
+    revision = int(revision)
+
+    # Calculate the distance, where it measures how far the last revision is

[aarya, 2014/08/14 20:22:20]

Can you stop by and help me understand what do you mean and how are using
distance all over the place.

[jeun, 2014/08/14 22:16:48]

Done.

+    # from the regression.
+    if range_start and range_end:
+      self.distance = min(abs(revision - range_start),
+                          abs(revision - range_end))
+
+    # If the regression is in SVN but it does not have regression info, check
+    # how far the last revision is from crash revision.
+    elif not utils.IsGitHash(crash_revision):
+      self.distance = abs(int(crash_revision) - revision)
+
+
+class BlameList(object):
+  """Represents a list of blame objects.
+
+  Thread-safe.
+  """
+
+  def __init__(self):
+    self.blame_list = []
+    self.blame_list_lock = Lock()
+
+  def __getitem__(self, index):
+    return self.blame_list[index]
+
+  def FindBlame(self, callstack, crash_revision_dict, regression_dict, parsers,
+                top_n_frames=10):
+    """Given a stack within a stacktrace, retrieves blame information.
+
+    Only either first 'top_n_frames' or the length of stack, whichever is
+    shorter, results are returned. The default value of 'top_n_frames' is 10.
+
+    Args:
+      callstack: The list of stack frames.
+      crash_revision_dict: A dictionary that maps component to its crash
+                          revision.
+      regression_dict: A dictionary that maps component to its revision
+                          range.
+      parsers: A list of two parsers, svn_parser and git_parser
+      top_n_frames: A number of stack frames to show the blame result for.
+    """
+    # Only return blame information for first 'top_n_frames' frames.
+    stack_frames = callstack.GetTopNFrames(top_n_frames)
+
+    threads = []
+    # Iterate through frames in stack.
+    for stack_frame in stack_frames:
+      # If the component this line is from does not have a crash revision,
+      # It is not possible to get blame information so ignore this line.

[aarya, 2014/08/14 20:22:20]

s/It/it
s/so/, so

[jeun, 2014/08/14 22:16:47]

Done.

+      component_path = stack_frame.component_path
+      if component_path not in crash_revision_dict:
+        continue
+
+      crash_revision = crash_revision_dict[component_path]['revision']
+      range_start = None
+      range_end = None
+      is_git = utils.IsGitHash(crash_revision)
+
+      repository_parser = parsers[1 if is_git else 0]

[aarya, 2014/08/14 20:22:20]

parsers should be a dict. parsers['git'] and parsers['svn'], don't use 0 and 1.

[jeun, 2014/08/14 22:16:47]

Done.

+
+      # If the revision is in SVN, and if regression information is available,
+      # get it. Not for Git because we cannot calculate the distance.
+      if not is_git:
+        if regression_dict and component_path in regression_dict:
+          component_object = regression_dict[component_path]
+          range_start = int(component_object['old_revision'])
+          range_end = int(component_object['new_revision'])
+
+      # Generate blame entry, one thread for one entry.
+      blame_thread = Thread(
+          target=self.__GenerateBlameEntry,
+          args=[repository_parser, stack_frame, crash_revision,
+                range_start, range_end])
+      threads.append(blame_thread)
+      blame_thread.start()
+
+    # Join the results before returning.
+    for blame_thread in threads:
+      blame_thread.join()
+
+  def __GenerateBlameEntry(self, repository_parser, stack_frame,

[aarya, 2014/08/14 20:22:21]

Why does the name start with __

[jeun, 2014/08/14 22:16:48]

It is because the function is used only in this class.

+                           crash_revision, range_start, range_end):
+    """Generates blame list from the arguments."""
+    stack_frame_index = stack_frame.index
+    component_path = stack_frame.component_path
+    component_name = stack_frame.component_name
+    file_name = stack_frame.file_name
+    file_path = stack_frame.file_path
+    line = stack_frame.crashed_line_number

[aarya, 2014/08/14 20:22:20]

s/crashed_line_number/crash_line_number
s/line/crash_line_number . better to use same naming convention.

[jeun, 2014/08/14 22:16:48]

Done.

+
+    # Parse blame information.
+    parsed_blame_info = repository_parser.ParseBlameInfo(
+        component_path, file_path, line, crash_revision)
+
+    # If it fails to retrieve information, do not do anything.
+    if not parsed_blame_info:

[aarya, 2014/08/14 20:22:21]

can you check list length so that we don't error on next line.

[jeun, 2014/08/14 22:16:48]

Done.

+      return
+
+    # Create blame object from the parsed info and add it to the list.
+    (content, revision, author, url) = parsed_blame_info
+    blame = Blame(content, component_name, stack_frame_index, file_name, line,
+                  author, crash_revision, revision, url,
+                  range_start, range_end)
+
+    with self.blame_list_lock:
+      self.blame_list.append(blame)
+
+  def FilterAndSortBlameList(self):
+    """Filters and sorts the blame list."""
+    # Sort the blame list by its distance, and its position in stack.
+    self.blame_list.sort(key=lambda blame: (blame.distance,
+                                            blame.stack_frame_index))
+
+    filtered_blame_list = []
+
+    for blame in self.blame_list:
+      # If regression information is available, check if it needs to be
+      # filtered.
+      if blame.range_start and blame.range_end:
+
+        # Discards results that are too far from the regression.
+        # For example, if regression is 10000:11000, it is very not
+        # likely that a commit from revision 1000 would have caused a crash.
+        if (blame.distance > blame.range_start / 4) and (

[aarya, 2014/08/14 20:22:21]

This rule makes no sense, why are you adding this or why is this needed. How has
this helped in results.

[jeun, 2014/08/14 22:16:48]

Done.

+            blame.distance > blame.range_end / 4):
+          continue
+
+        filtered_blame_list.append(blame)
+    self.blame_list = filtered_blame_list