debian-mirror-gitlab/lib/gitlab/diff/position_tracer.rb
2019-02-15 15:39:39 +05:30

233 lines
9.7 KiB
Ruby

# frozen_string_literal: true
# Finds the diff position in the new diff that corresponds to the same location
# specified by the provided position in the old diff.
module Gitlab
module Diff
class PositionTracer
attr_accessor :project
attr_accessor :old_diff_refs
attr_accessor :new_diff_refs
attr_accessor :paths
def initialize(project:, old_diff_refs:, new_diff_refs:, paths: nil)
@project = project
@old_diff_refs = old_diff_refs
@new_diff_refs = new_diff_refs
@paths = paths
end
def trace(ab_position)
return unless old_diff_refs&.complete? && new_diff_refs&.complete?
return unless ab_position.diff_refs == old_diff_refs
# Suppose we have an MR with source branch `feature` and target branch `master`.
# When the MR was created, the head of `master` was commit A, and the
# head of `feature` was commit B, resulting in the original diff A->B.
# Since creation, `master` was updated to C.
# Now `feature` is being updated to D, and the newly generated MR diff is C->D.
# It is possible that C and D are direct descendants of A and B respectively,
# but this isn't necessarily the case as rebases and merges come into play.
#
# Suppose we have a diff note on the original diff A->B. Now that the MR
# is updated, we need to find out what line in C->D corresponds to the
# line the note was originally created on, so that we can update the diff note's
# records and continue to display it in the right place in the diffs.
# If we cannot find this line in the new diff, this means the diff note is now
# outdated, and we will display that fact to the user.
#
# In the new diff, the file the diff note was originally created on may
# have been renamed, deleted or even created, if the file existed in A and B,
# but was removed in C, and restored in D.
#
# Every diff note stores a Position object that defines a specific location,
# identified by paths and line numbers, within a specific diff, identified
# by start, head and base commit ids.
#
# For diff notes for diff A->B, the position looks like this:
# Position
# start_sha - ID of commit A
# head_sha - ID of commit B
# base_sha - ID of base commit of A and B
# old_path - path as of A (nil if file was newly created)
# new_path - path as of B (nil if file was deleted)
# old_line - line number as of A (nil if file was newly created)
# new_line - line number as of B (nil if file was deleted)
#
# We can easily update `start_sha` and `head_sha` to hold the IDs of
# commits C and D, and can trivially determine `base_sha` based on those,
# but need to find the paths and line numbers as of C and D.
#
# If the file was unchanged or newly created in A->B, the path as of D can be found
# by generating diff B->D ("head to head"), finding the diff file with
# `diff_file.old_path == position.new_path`, and taking `diff_file.new_path`.
# The path as of C can be found by taking diff C->D, finding the diff file
# with that same `new_path` and taking `diff_file.old_path`.
# The line number as of D can be found by using the LineMapper on diff B->D
# and providing the line number as of B.
# The line number as of C can be found by using the LineMapper on diff C->D
# and providing the line number as of D.
#
# If the file was deleted in A->B, the path as of C can be found
# by generating diff A->C ("base to base"), finding the diff file with
# `diff_file.old_path == position.old_path`, and taking `diff_file.new_path`.
# The path as of D can be found by taking diff C->D, finding the diff file
# with `old_path` set to that `diff_file.new_path` and taking `diff_file.new_path`.
# The line number as of C can be found by using the LineMapper on diff A->C
# and providing the line number as of A.
# The line number as of D can be found by using the LineMapper on diff C->D
# and providing the line number as of C.
if ab_position.added?
trace_added_line(ab_position)
elsif ab_position.removed?
trace_removed_line(ab_position)
else # unchanged
trace_unchanged_line(ab_position)
end
end
private
def trace_added_line(ab_position)
b_path = ab_position.new_path
b_line = ab_position.new_line
bd_diff = bd_diffs.diff_file_with_old_path(b_path)
d_path = bd_diff&.new_path || b_path
d_line = LineMapper.new(bd_diff).old_to_new(b_line)
if d_line
cd_diff = cd_diffs.diff_file_with_new_path(d_path)
c_path = cd_diff&.old_path || d_path
c_line = LineMapper.new(cd_diff).new_to_old(d_line)
if c_line
# If the line is still in D but also in C, it has turned from an
# added line into an unchanged one.
new_position = position(cd_diff, c_line, d_line)
if valid_position?(new_position)
# If the line is still in the MR, we don't treat this as outdated.
{ position: new_position, outdated: false }
else
# If the line is no longer in the MR, we unfortunately cannot show
# the current state on the CD diff, so we treat it as outdated.
ac_diff = ac_diffs.diff_file_with_new_path(c_path)
{ position: position(ac_diff, nil, c_line), outdated: true }
end
else
# If the line is still in D and not in C, it is still added.
{ position: position(cd_diff, nil, d_line), outdated: false }
end
else
# If the line is no longer in D, it has been removed from the MR.
{ position: position(bd_diff, b_line, nil), outdated: true }
end
end
def trace_removed_line(ab_position)
a_path = ab_position.old_path
a_line = ab_position.old_line
ac_diff = ac_diffs.diff_file_with_old_path(a_path)
c_path = ac_diff&.new_path || a_path
c_line = LineMapper.new(ac_diff).old_to_new(a_line)
if c_line
cd_diff = cd_diffs.diff_file_with_old_path(c_path)
d_path = cd_diff&.new_path || c_path
d_line = LineMapper.new(cd_diff).old_to_new(c_line)
if d_line
# If the line is still in C but also in D, it has turned from a
# removed line into an unchanged one.
bd_diff = bd_diffs.diff_file_with_new_path(d_path)
{ position: position(bd_diff, nil, d_line), outdated: true }
else
# If the line is still in C and not in D, it is still removed.
{ position: position(cd_diff, c_line, nil), outdated: false }
end
else
# If the line is no longer in C, it has been removed outside of the MR.
{ position: position(ac_diff, a_line, nil), outdated: true }
end
end
def trace_unchanged_line(ab_position)
a_path = ab_position.old_path
a_line = ab_position.old_line
b_path = ab_position.new_path
b_line = ab_position.new_line
ac_diff = ac_diffs.diff_file_with_old_path(a_path)
c_path = ac_diff&.new_path || a_path
c_line = LineMapper.new(ac_diff).old_to_new(a_line)
bd_diff = bd_diffs.diff_file_with_old_path(b_path)
d_line = LineMapper.new(bd_diff).old_to_new(b_line)
cd_diff = cd_diffs.diff_file_with_old_path(c_path)
if c_line && d_line
# If the line is still in C and D, it is still unchanged.
new_position = position(cd_diff, c_line, d_line)
if valid_position?(new_position)
# If the line is still in the MR, we don't treat this as outdated.
{ position: new_position, outdated: false }
else
# If the line is no longer in the MR, we unfortunately cannot show
# the current state on the CD diff or any change on the BD diff,
# so we treat it as outdated.
{ position: nil, outdated: true }
end
elsif d_line # && !c_line
# If the line is still in D but no longer in C, it has turned from
# an unchanged line into an added one.
# We don't treat this as outdated since the line is still in the MR.
{ position: position(cd_diff, nil, d_line), outdated: false }
else # !d_line && (c_line || !c_line)
# If the line is no longer in D, it has turned from an unchanged line
# into a removed one.
{ position: position(bd_diff, b_line, nil), outdated: true }
end
end
def ac_diffs
@ac_diffs ||= compare(
old_diff_refs.base_sha || old_diff_refs.start_sha,
new_diff_refs.base_sha || new_diff_refs.start_sha,
straight: true
)
end
def bd_diffs
@bd_diffs ||= compare(old_diff_refs.head_sha, new_diff_refs.head_sha, straight: true)
end
def cd_diffs
@cd_diffs ||= compare(new_diff_refs.start_sha, new_diff_refs.head_sha)
end
def compare(start_sha, head_sha, straight: false)
compare = CompareService.new(project, head_sha).execute(project, start_sha, straight: straight)
compare.diffs(paths: paths, expanded: true)
end
def position(diff_file, old_line, new_line)
Position.new(diff_file: diff_file, old_line: old_line, new_line: new_line)
end
def valid_position?(position)
!!position.diff_line(project.repository)
end
end
end
end