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# outdated, and we will display that fact to the user.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