diff options
Diffstat (limited to 'lib/gitlab/diff/position_tracer/line_strategy.rb')
| -rw-r--r-- | lib/gitlab/diff/position_tracer/line_strategy.rb | 201 |
1 files changed, 201 insertions, 0 deletions
diff --git a/lib/gitlab/diff/position_tracer/line_strategy.rb b/lib/gitlab/diff/position_tracer/line_strategy.rb new file mode 100644 index 00000000000..8db0fc6f963 --- /dev/null +++ b/lib/gitlab/diff/position_tracer/line_strategy.rb @@ -0,0 +1,201 @@ +# frozen_string_literal: true + +module Gitlab + module Diff + class PositionTracer + class LineStrategy < BaseStrategy + def trace(position) + # 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 + # If we cannot find this line in the new diff, this means the diff note is now + # outdated, and we will display that fact to the user.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 position.added? + trace_added_line(position) + elsif position.removed? + trace_removed_line(position) + else # unchanged + trace_unchanged_line(position) + end + end + + private + + def trace_added_line(position) + b_path = position.new_path + b_line = 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 = new_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: new_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: new_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: new_position(bd_diff, b_line, nil), outdated: true } + end + end + + def trace_removed_line(position) + a_path = position.old_path + a_line = 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: new_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: new_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: new_position(ac_diff, a_line, nil), outdated: true } + end + end + + def trace_unchanged_line(position) + a_path = position.old_path + a_line = position.old_line + b_path = position.new_path + b_line = 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 = new_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: new_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: new_position(bd_diff, b_line, nil), outdated: true } + end + end + + def new_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 +end |