Fix Bitbucket Cloud importer omitting replies

Inline diff comments did not have the proper position, so even though
they had line codes the merge request validation would fail. Now
we cache the line position for each parent comment and use that.

Closes #50052

changelogs/unreleased/sh-fix-bitbucket-cloud-importer-replies.yml

+---
+title: Fix Bitbucket Cloud importer omitting replies
+merge_request: 21076
+author:
+type: fixed

lib/gitlab/bitbucket_import/importer.rb

@@ -188,7 +188,8 @@ module Gitlab
       end
 
       def import_inline_comments(inline_comments, pull_request, merge_request)
-        line_code_map = {}
+        position_map = {}
+        discussion_map = {}
 
         children, parents = inline_comments.partition(&:has_parent?)
 
@@ -196,22 +197,28 @@ module Gitlab
         # relationships. We assume that the child can appear in any order in
         # the JSON.
         parents.each do |comment|
-          line_code_map[comment.iid] = generate_line_code(comment)
+          position_map[comment.iid] = build_position(merge_request, comment)
         end
 
         children.each do |comment|
-          line_code_map[comment.iid] = line_code_map.fetch(comment.parent_id, nil)
+          position_map[comment.iid] = position_map.fetch(comment.parent_id, nil)
         end
 
         inline_comments.each do |comment|
           begin
             attributes = pull_request_comment_attributes(comment)
+            attributes[:discussion_id] = discussion_map[comment.parent_id] if comment.has_parent?
+
             attributes.merge!(
-              position: build_position(merge_request, comment),
-              line_code: line_code_map.fetch(comment.iid),
+              position: position_map[comment.iid],
               type: 'DiffNote')
 
-            merge_request.notes.create!(attributes)
+            note = merge_request.notes.create!(attributes)
+
+            # We can't store a discussion ID until a note is created, so if
+            # replies are created before the parent the discussion ID won't be
+            # linked properly.
+            discussion_map[comment.iid] = note.discussion_id
           rescue StandardError => e
             errors << { type: :pull_request, iid: comment.iid, errors: e.message }
           end
@@ -240,10 +247,6 @@ module Gitlab
         end
       end
 
-      def generate_line_code(pr_comment)
-        Gitlab::Git.diff_line_code(pr_comment.file_path, pr_comment.new_pos, pr_comment.old_pos)
-      end
-
       def pull_request_comment_attributes(comment)
         {
           project: project,

spec/lib/gitlab/bitbucket_import/importer_spec.rb

@@ -69,6 +69,7 @@ describe Gitlab::BitbucketImport::Importer do
   let(:project) do
     create(
       :project,
+      :repository,
       import_source: project_identifier,
       import_url: "https://bitbucket.org/#{project_identifier}.git",
       import_data_attributes: { credentials: data }
@@ -85,10 +86,84 @@ describe Gitlab::BitbucketImport::Importer do
     }
   end
 
+  let(:sample) { RepoHelpers.sample_compare }
+
   before do
     allow(importer).to receive(:gitlab_shell) { gitlab_shell }
   end
 
+  subject { described_class.new(project) }
+
+  describe '#import_pull_requests' do
+    before do
+      allow(subject).to receive(:import_wiki)
+      allow(subject).to receive(:import_issues)
+
+      pull_request = instance_double(
+        Bitbucket::Representation::PullRequest,
+        iid: 10,
+        source_branch_sha: sample.commits.last,
+        source_branch_name: Gitlab::Git::BRANCH_REF_PREFIX + sample.source_branch,
+        target_branch_sha: sample.commits.first,
+        target_branch_name: Gitlab::Git::BRANCH_REF_PREFIX + sample.target_branch,
+        title: 'This is a title',
+        description: 'This is a test pull request',
+        state: 'merged',
+        author: 'other',
+        created_at: Time.now,
+        updated_at: Time.now)
+
+      # https://gitlab.com/gitlab-org/gitlab-test/compare/c1acaa58bbcbc3eafe538cb8274ba387047b69f8...5937ac0a7beb003549fc5fd26fc247ad
+      @inline_note = instance_double(
+        Bitbucket::Representation::PullRequestComment,
+        iid: 2,
+        file_path: '.gitmodules',
+        old_pos: nil,
+        new_pos: 4,
+        note: 'Hello world',
+        author: 'root',
+        created_at: Time.now,
+        updated_at: Time.now,
+        inline?: true,
+        has_parent?: false)
+
+      @reply = instance_double(
+        Bitbucket::Representation::PullRequestComment,
+        iid: 3,
+        file_path: '.gitmodules',
+        note: 'Hello world',
+        author: 'root',
+        created_at: Time.now,
+        updated_at: Time.now,
+        inline?: true,
+        has_parent?: true,
+        parent_id: 2)
+
+      comments = [@inline_note, @reply]
+
+      allow(subject.client).to receive(:repo)
+      allow(subject.client).to receive(:pull_requests).and_return([pull_request])
+      allow(subject.client).to receive(:pull_request_comments).with(anything, pull_request.iid).and_return(comments)
+    end
+
+    it 'imports threaded discussions' do
+      expect { subject.execute }.to change { MergeRequest.count }.by(1)
+
+      merge_request = MergeRequest.first
+      expect(merge_request.notes.count).to eq(2)
+      expect(merge_request.notes.map(&:discussion_id).uniq.count).to eq(1)
+
+      notes = merge_request.notes.order(:id).to_a
+      start_note = notes.first
+      expect(start_note).to be_a(DiffNote)
+      expect(start_note.note).to eq(@inline_note.note)
+
+      reply_note = notes.last
+      expect(reply_note).to be_a(DiffNote)
+      expect(reply_note.note).to eq(@reply.note)
+    end
+  end
+
   context 'issues statuses' do
     before do
       # HACK: Bitbucket::Representation.const_get('Issue') seems to return ::Issue without this