Fixes for Parallel Working Branch strategy (#592)

- Fix retry for finalize to not create multiple PRs
- Check for diff between branches before creating PR

app/controllers/releases_controller.rb

@@ -124,9 +124,9 @@ def set_release
   end
 
   def set_pull_requests
-    @pre_release_prs = @release.pull_requests.pre_release
-    @post_release_prs = @release.pull_requests.post_release
-    @ongoing_open_release_prs = @release.pull_requests.ongoing.open
+    @pre_release_prs = @release.pre_release_prs
+    @post_release_prs = @release.post_release_prs
+    @ongoing_open_release_prs = @release.backmerge_prs.open
   end
 
   def set_commits

app/libs/installations/github/api.rb

@@ -217,6 +217,8 @@ def branch_exists?(repo, branch_name)
     end
 
     def create_pr!(repo, to, from, title, body, transforms)
+      raise Installations::Errors::PullRequestWithoutCommits unless diff?(repo, to, from)
+
       execute do
         @client
           .create_pull_request(repo, to, from, title, body)
@@ -258,6 +260,15 @@ def commits_between(repo, from_branch, to_branch, transforms)
       end
     end
 
+    def diff?(repo, from_branch, to_branch)
+      execute do
+        @client
+          .compare(repo, from_branch, to_branch)
+          .dig(:files)
+          .present?
+      end
+    end
+
     def head(repo, working_branch_name, sha_only: true, commit_transforms: nil)
       raise ArgumentError, "transforms must be supplied when querying head object" if !sha_only && !commit_transforms
 

app/libs/triggers/post_release/parallel_branches.rb

@@ -26,7 +26,8 @@ def create_and_merge_pr
         to_branch_ref: working_branch,
         from_branch_ref: release_branch,
         title: pr_title,
-        description: pr_description
+        description: pr_description,
+        existing_pr: release.pull_requests.post_release.first
       ).then do |value|
         stamp_pr_success
         GitHub::Result.new { value }

app/libs/triggers/release.rb

@@ -54,6 +54,7 @@ def call
         raise ReleaseAlreadyInProgress.new("No more releases can be started until the ongoing release is finished!") if train.upcoming_release.present?
         raise UpcomingReleaseNotAllowed.new("Upcoming releases are not allowed for your train.") if train.ongoing_release.present? && !train.upcoming_release_startable?
         raise NothingToRelease.new("No diff since last release") if regular_release? && !train.diff_since_last_release?
+        raise NothingToRelease.new("No diff between working and release branch") if train.parallel_working_branch? && !train.diff_for_release?
         train.activate! unless train.active?
         create_release
         train.create_webhook!

app/models/github_integration.rb

@@ -272,6 +272,10 @@ def commit_log(from_branch, to_branch)
     installation.commits_between(code_repository_name, from_branch, to_branch, COMMITS_TRANSFORMATIONS)
   end
 
+  def diff_between?(from_branch, to_branch)
+    installation.diff?(code_repository_name, from_branch, to_branch)
+  end
+
   def public_icon_img
     PUBLIC_ICON
   end

app/models/gitlab_integration.rb

@@ -219,6 +219,10 @@ def commit_log(from_branch, to_branch)
     with_api_retries { installation.commits_between(code_repository_name, from_branch, to_branch, COMMITS_BETWEEN_TRANSFORMATIONS) }
   end
 
+  def diff_between?(from_branch, to_branch)
+    with_api_retries { installation.diff?(code_repository_name, from_branch, to_branch) }
+  end
+
   def create_patch_pr!(to_branch, patch_branch, commit_hash, pr_title_prefix)
     # FIXME
     {}.merge_if_present(source: :gitlab)

app/models/release.rb

@@ -135,7 +135,7 @@ class Release < ApplicationRecord
   attr_accessor :has_major_bump, :force_finalize, :hotfix_platform, :custom_version
 
   delegate :versioning_strategy, to: :train
-  delegate :app, :pre_release_prs?, :vcs_provider, :release_platforms, :notify!, :continuous_backmerge?, to: :train
+  delegate :app, :vcs_provider, :release_platforms, :notify!, :continuous_backmerge?, to: :train
   delegate :platform, to: :app
 
   def self.pending_release?
@@ -161,6 +161,14 @@ def backmerge_prs
     pull_requests.ongoing
   end
 
+  def post_release_prs
+    pull_requests.post_release
+  end
+
+  def pre_release_prs
+    pull_requests.pre_release
+  end
+
   def duration
     return unless finished?
     ActiveSupport::Duration.build(completed_at - scheduled_at)

app/models/train.rb

@@ -186,9 +186,14 @@ def last_run_at
   end
 
   def diff_since_last_release?
-    return vcs_provider.commit_log(ongoing_release.first_commit.commit_hash, working_branch).any? if ongoing_release
+    return vcs_provider.diff_between?(ongoing_release.first_commit.commit_hash, working_branch) if ongoing_release
     return true if last_finished_release.blank?
-    vcs_provider.commit_log(last_finished_release.tag_name || last_finished_release.last_commit.commit_hash, working_branch).any?
+    vcs_provider.diff_between?(last_finished_release.tag_name || last_finished_release.last_commit.commit_hash, working_branch)
+  end
+
+  def diff_for_release?
+    return false unless parallel_working_branch?
+    vcs_provider.diff_between?(release_branch, working_branch)
   end
 
   def create_webhook!
@@ -328,7 +333,7 @@ def open_active_prs_for(branch_name)
     PullRequest.open.where(release_id: active_runs.ids, head_ref: branch_name)
   end
 
-  def pre_release_prs?
+  def parallel_working_branch?
     branching_strategy == "parallel_working"
   end
 

app/views/releases/show.html.erb

@@ -44,7 +44,7 @@
   <div>
     <%= render partial: "shared/live_release/kick_off", locals: { release: @release, release_train: @train } %>
 
-    <% if @release.pre_release_prs? %>
+    <% if @pre_release_prs.present? %>
       <%= render partial: "shared/live_release/separator", locals: { margin_only: true } %>
       <%= render partial: "shared/live_release/pre_release_prs", locals: { pre_release_prs: @pre_release_prs } %>
     <% end %>

spec/libs/triggers/release_spec.rb

@@ -16,7 +16,7 @@
       allow_any_instance_of(GooglePlayStoreIntegration).to receive(:draft_check?).and_return(false)
       allow(Installations::Github::Jwt).to receive(:new).and_return(github_jwt_double)
       allow(Installations::Github::Api).to receive(:new).and_return(github_api_double)
-      allow(github_api_double).to receive(:commits_between).and_return([1])
+      allow(github_api_double).to receive(:diff?).and_return(true)
     end
 
     it "creates a new release" do