Enable auto merge for PRs when when the first merge attampt fails

- This will ensure that we try to merge PRs for repositories which do not have the
auto merge feature available

app/libs/triggers/pull_request.rb

@@ -54,16 +54,19 @@ def create_and_merge!
     pr_in_work.reload
     return GitHub::Result.new { pr_in_work } if pr_in_work.closed?
 
-    # enable auto-merge if possible and avoid merging manually
-    if enable_auto_merge?
-      repo_integration.enable_auto_merge!(pr_in_work.number)
-      return GitHub::Result.new { pr_in_work }
-    end
-
     # try and merge, when:
     # - create PR is successful
     # - or PR already exists and is _not_ already closed
-    merge!(pr_in_work).then { GitHub::Result.new { pr_in_work.close! } }
+    merge_result = merge!(pr_in_work)
+    if merge_result.ok?
+      pr_in_work.close!
+    elsif enable_auto_merge? # enable auto-merge if possible
+      repo_integration.enable_auto_merge!(pr_in_work.number)
+    else
+      return merge_result
+    end
+
+    GitHub::Result.new { pr_in_work }
   end
 
   private

spec/libs/triggers/pull_request_spec.rb

@@ -26,7 +26,7 @@
     let(:merge_payload) { JSON.parse(File.read("spec/fixtures/github/merge_pull_request.json")).with_indifferent_access }
 
     it "creates a PR for the release" do
-      allow(repo_integration).to receive_messages(create_pr!: create_payload, enable_auto_merge: true)
+      allow(repo_integration).to receive_messages(create_pr!: create_payload, merge_pr!: merge_payload, enable_auto_merge: true)
 
       result = described_class.create_and_merge!(
         release: release,
@@ -44,7 +44,7 @@
     end
 
     it "creates a patch PR for the commit" do
-      allow(repo_integration).to receive_messages(cherry_pick_pr: create_payload, enable_auto_merge: true)
+      allow(repo_integration).to receive_messages(cherry_pick_pr: create_payload, merge_pr!: merge_payload, enable_auto_merge: true)
       commit = create(:commit, release:)
       patch_branch = "patch-main-#{commit.commit_hash}"
 
@@ -64,8 +64,25 @@
       expect(commit.reload.pull_request).to be_present
     end
 
-    it "does not merge the PR if auto merge is enabled" do
+    it "merges the PR" do
+      allow(repo_integration).to receive_messages(create_pr!: create_payload, merge_pr!: merge_payload, enable_auto_merge: true)
+
+      result = described_class.create_and_merge!(
+        release: release,
+        new_pull_request: release.pull_requests.post_release.open.build,
+        to_branch_ref: working_branch,
+        from_branch_ref: release_branch,
+        title: pr_title,
+        description: pr_description
+      )
+      expect(repo_integration).to have_received(:merge_pr!).with(repo_name, result.value!.number)
+      expect(result.ok?).to be(true)
+      expect(release.reload.pull_requests.size).to eq(1)
+    end
+
+    it "enables auto merge if merge fails" do
       allow(repo_integration).to receive_messages(cherry_pick_pr: create_payload, enable_auto_merge: true)
+      allow(repo_integration).to receive(:merge_pr!).and_raise(Installations::Error.new("Failed to merge the Pull Request", reason: :pull_request_not_mergeable))
       commit = create(:commit, release:)
       patch_branch = "patch-main-#{commit.commit_hash}"
 
@@ -83,6 +100,7 @@
       created_pr = commit.reload.pull_request
 
       expect(repo_integration).to have_received(:cherry_pick_pr).with(repo_name, working_branch, commit.commit_hash, patch_branch, pr_title, pr_description, GithubIntegration::PR_TRANSFORMATIONS)
+      expect(repo_integration).to have_received(:merge_pr!).with(repo_name, created_pr.number)
       expect(repo_integration).to have_received(:enable_auto_merge).with(app.config.code_repo_namespace, app.config.code_repo_name_only, created_pr.number)
       expect(result.ok?).to be(true)
       expect(created_pr).to be_present
@@ -91,7 +109,6 @@
 
     it "does not create PR if the PR does not have a diff to create" do
       allow(repo_integration).to receive(:create_pr!).and_raise(no_diff_error)
-      allow(repo_integration).to receive(:enable_auto_merge)
 
       result = described_class.create_and_merge!(
         release: release,
@@ -105,14 +122,12 @@
       namespaced_release_branch = "#{release.train.app.config.code_repo_namespace}:#{release_branch}"
 
       expect(repo_integration).to have_received(:create_pr!).with(repo_name, working_branch, namespaced_release_branch, pr_title, pr_description, GithubIntegration::PR_TRANSFORMATIONS)
-      expect(repo_integration).not_to have_received(:enable_auto_merge)
       expect(result.ok?).to be(true)
       expect(release.reload.pull_requests.size).to eq(0)
     end
 
     it "returns an unsuccessful result if the PR does not have a diff to create and allow without diff is false" do
       allow(repo_integration).to receive(:create_pr!).and_raise(no_diff_error)
-      allow(repo_integration).to receive(:enable_auto_merge)
 
       result = described_class.create_and_merge!(
         release: release,
@@ -126,7 +141,6 @@
       namespaced_release_branch = "#{release.train.app.config.code_repo_namespace}:#{release_branch}"
 
       expect(repo_integration).to have_received(:create_pr!).with(repo_name, working_branch, namespaced_release_branch, pr_title, pr_description, GithubIntegration::PR_TRANSFORMATIONS)
-      expect(repo_integration).not_to have_received(:enable_auto_merge)
       expect(result.ok?).to be(false)
       expect(release.reload.pull_requests.size).to eq(0)
     end