Split MR widget into cached and non-cached serializers

Splits auto-refreshing of MR widget into 2 requests:

- the one which uses etag-caching and invalidates the fields on change
- the one without caching

The idea is to gradually move all the fields to etag-cached endpoint

5 files changed, 173 insertions, 143 deletions

diff --git a/spec/controllers/projects/merge_requests/content_controller_spec.rb b/spec/controllers/projects/merge_requests/content_controller_spec.rb
index 2879e06aee4..818cf794ec6 100644
--- a/spec/controllers/projects/merge_requests/content_controller_spec.rb
+++ b/spec/controllers/projects/merge_requests/content_controller_spec.rb
@@ -11,8 +11,8 @@ describe Projects::MergeRequests::ContentController do
     sign_in(user)
   end
 
-  def do_request
-    get :widget, params: {
+  def do_request(action = :cached_widget)
+    get action, params: {
       namespace_id: project.namespace.to_param,
       project_id: project,
       id: merge_request.iid,
@@ -20,41 +20,65 @@ describe Projects::MergeRequests::ContentController do
     }
   end
 
-  describe 'GET widget' do
-    context 'user has access to the project' do
-      before do
-        expect(::Gitlab::GitalyClient).to receive(:allow_ref_name_caching).and_call_original
+  context 'user has access to the project' do
+    before do
+      expect(::Gitlab::GitalyClient).to receive(:allow_ref_name_caching).and_call_original
 
-        project.add_maintainer(user)
-      end
+      project.add_maintainer(user)
+    end
 
+    describe 'GET cached_widget' do
       it 'renders widget MR entity as json' do
         do_request
 
-        expect(response).to match_response_schema('entities/merge_request_widget')
+        expect(response).to match_response_schema('entities/merge_request_poll_cached_widget')
       end
 
+      it 'closes an MR with moved source project' do
+        merge_request.update_column(:source_project_id, nil)
+
+        expect { do_request }.to change { merge_request.reload.open? }.from(true).to(false)
+      end
+    end
+
+    describe 'GET widget' do
       it 'checks whether the MR can be merged' do
         controller.instance_variable_set(:@merge_request, merge_request)
 
         expect(merge_request).to receive(:check_mergeability)
 
-        do_request
+        do_request(:widget)
       end
 
-      it 'closes an MR with moved source project' do
-        merge_request.update_column(:source_project_id, nil)
+      context 'merged merge request' do
+        let(:merge_request) do
+          create(:merged_merge_request, :with_test_reports, target_project: project, source_project: project)
+        end
 
-        expect { do_request }.to change { merge_request.reload.open? }.from(true).to(false)
+        it 'renders widget MR entity as json' do
+          do_request(:widget)
+
+          expect(response).to match_response_schema('entities/merge_request_poll_widget')
+        end
       end
     end
+  end
 
-    context 'user does not have access to the project' do
-      it 'renders widget MR entity as json' do
+  context 'user does not have access to the project' do
+    describe 'GET cached_widget' do
+      it 'returns 404' do
         do_request
 
         expect(response).to have_http_status(:not_found)
       end
     end
+
+    describe 'GET widget' do
+      it 'returns 404' do
+        do_request(:widget)
+
+        expect(response).to have_http_status(:not_found)
+      end
+    end
   end
 end
diff --git a/spec/fixtures/api/schemas/entities/merge_request_poll_cached_widget.json b/spec/fixtures/api/schemas/entities/merge_request_poll_cached_widget.json
new file mode 100644
index 00000000000..e8959307767
--- /dev/null
+++ b/spec/fixtures/api/schemas/entities/merge_request_poll_cached_widget.json
@@ -0,0 +1,46 @@
+{
+  "type": "object",
+  "properties" : {
+    "id": { "type": "integer" },
+    "iid": { "type": "integer" },
+    "description": { "type": ["string", "null"] },
+    "title": { "type": "string" },
+    "auto_merge_enabled": { "type": "boolean" },
+    "state": { "type": "string" },
+    "merge_commit_sha": { "type": ["string", "null"] },
+    "short_merge_commit_sha": { "type": ["string", "null"] },
+    "merge_error": { "type": ["string", "null"] },
+    "merge_status": { "type": "string" },
+    "merge_user_id": { "type": ["integer", "null"] },
+    "source_branch": { "type": "string" },
+    "source_project_id": { "type": "integer" },
+    "target_branch": { "type": "string" },
+    "target_branch_sha": { "type": "string" },
+    "target_project_id": { "type": "integer" },
+    "squash": { "type": "boolean" },
+    "rebase_in_progress": { "type": "boolean" },
+    "default_squash_commit_message": { "type": "string" },
+    "commits_count": { "type": ["integer", "null"] },
+    "merge_ongoing": { "type": "boolean" },
+    "work_in_progress": { "type": "boolean" },
+    "has_conflicts": { "type": "boolean" },
+    "can_be_merged": { "type": "boolean" },
+    "remove_source_branch": { "type": ["boolean", "null"] },
+    "source_branch_exists": { "type": "boolean" },
+    "branch_missing": { "type": "boolean" },
+    "commits_without_merge_commits": { "type": "array" },
+    "diff_head_sha": { "type": ["string", "null"] },
+    "metrics": {
+      "oneOf": [
+        { "type": "null" },
+        { "$ref": "merge_request_metrics.json" }
+      ]
+    },
+    "diverged_commits_count": { "type": "integer" },
+    "target_branch_commits_path": { "type": "string" },
+    "target_branch_tree_path": { "type": "string" },
+    "merge_commit_path": { "type": ["string", "null"] },
+    "source_branch_with_namespace_link": { "type": "string" },
+    "source_branch_path": { "type": "string" }
+  }
+}
diff --git a/spec/fixtures/api/schemas/entities/merge_request_poll_widget.json b/spec/fixtures/api/schemas/entities/merge_request_poll_widget.json
new file mode 100644
index 00000000000..2052892dfa3
--- /dev/null
+++ b/spec/fixtures/api/schemas/entities/merge_request_poll_widget.json
@@ -0,0 +1,55 @@
+{
+  "type": "object",
+  "properties" : {
+    "id": { "type": "integer" },
+    "iid": { "type": "integer" },
+    "description": { "type": ["string", "null"] },
+    "title": { "type": "string" },
+    "auto_merge_strategy": { "type": ["string", "null"] },
+    "available_auto_merge_strategies": { "type": "array" },
+    "source_branch_protected": { "type": "boolean" },
+    "allow_collaboration": { "type": "boolean"},
+    "should_be_rebased": { "type": "boolean" },
+    "ff_only_enabled": { "type": ["boolean", false] },
+    "merge_user": { "type": ["object", "null"] },
+    "pipeline": { "type": ["object", "null"] },
+    "merge_pipeline": { "type": ["object", "null"] },
+    "default_merge_commit_message": { "type": ["string", "null"] },
+    "mergeable": { "type": "boolean" },
+    "default_merge_commit_message_with_description": { "type": "string" },
+    "mergeable_discussions_state": { "type": "boolean" },
+    "project_archived": { "type": "boolean" },
+    "only_allow_merge_if_pipeline_succeeds": { "type": "boolean" },
+    "has_ci": { "type": "boolean" },
+    "ci_status": { "type": ["string", "null"] },
+    "cancel_auto_merge_path": { "type": ["string", "null"] },
+    "test_reports_path": { "type": ["string", "null"] },
+    "can_receive_suggestion": { "type": "boolean" },
+    "create_issue_to_resolve_discussions_path": { "type": ["string", "null"] },
+    "current_user": {
+      "type": "object",
+      "required": [
+        "can_remove_source_branch",
+        "can_revert_on_current_merge_request",
+        "can_cherry_pick_on_current_merge_request"
+      ],
+      "properties": {
+        "can_remove_source_branch": { "type": "boolean" },
+        "can_revert_on_current_merge_request": { "type": ["boolean", "null"] },
+        "can_cherry_pick_on_current_merge_request": { "type": ["boolean", "null"] },
+        "can_create_note": { "type": "boolean" },
+        "can_create_issue": { "type": "boolean" },
+        "can_update": { "type": "boolean" }
+      },
+      "additionalProperties": false
+    },
+    "can_push_to_source_branch": { "type": "boolean" },
+    "new_blob_path": { "type": ["string", "null"] },
+    "rebase_path": { "type": ["string", "null"] },
+    "conflict_resolution_path": { "type": ["string", "null"] },
+    "remove_wip_path": { "type": ["string", "null"] },
+    "merge_path": { "type": ["string", "null"] },
+    "cherry_pick_in_fork_path": { "type": ["string", "null"] },
+    "revert_in_fork_path": { "type": ["string", "null"] }
+  }
+}
diff --git a/spec/fixtures/api/schemas/entities/merge_request_widget.json b/spec/fixtures/api/schemas/entities/merge_request_widget.json
index eac1dbc6474..779a47222b7 100644
--- a/spec/fixtures/api/schemas/entities/merge_request_widget.json
+++ b/spec/fixtures/api/schemas/entities/merge_request_widget.json
@@ -1,132 +1,35 @@
 {
   "type": "object",
-  "properties" : {
-    "id": { "type": "integer" },
-    "iid": { "type": "integer" },
-    "author_id": { "type": "integer" },
-    "description": { "type": ["string", "null"] },
-    "lock_version": { "type": ["string", "null"] },
-    "milestone_id": { "type": ["string", "null"] },
-    "position": { "type": "integer" },
-    "state": { "type": "string" },
-    "title": { "type": "string" },
-    "updated_by_id": { "type": ["string", "null"] },
-    "created_at": { "type": "string" },
-    "updated_at": { "type": "string" },
-    "time_estimate": { "type": "integer" },
-    "total_time_spent": { "type": "integer" },
-    "human_time_estimate": { "type": ["integer", "null"] },
-    "human_total_time_spent": { "type": ["integer", "null"] },
-    "milestone": { "type": ["object", "null"] },
-    "labels": { "type": ["array", "null"] },
-    "in_progress_merge_commit_sha": { "type": ["string", "null"] },
-    "merge_error": { "type": ["string", "null"] },
-    "merge_commit_sha": { "type": ["string", "null"] },
-    "short_merge_commit_sha": { "type": ["string", "null"] },
-    "merge_params": { "type": ["object", "null"] },
-    "merge_status": { "type": "string" },
-    "merge_user_id": { "type": ["integer", "null"] },
-    "merge_when_pipeline_succeeds": { "type": "boolean" },
-    "source_branch": { "type": "string" },
-    "source_project_id": { "type": "integer" },
-    "source_project_full_path": { "type": ["string", "null"]},
-    "target_branch": { "type": "string" },
-    "target_project_id": { "type": "integer" },
-    "target_project_full_path": { "type": ["string", "null"]},
-    "allow_collaboration": { "type": "boolean"},
-    "metrics": {
-      "oneOf": [
-        { "type": "null" },
-        { "$ref": "merge_request_metrics.json" }
-      ]
-    },
-    "author": { "type": ["object", "null"] },
-    "merge_user": { "type": ["object", "null"] },
-    "diff_head_sha": { "type": ["string", "null"] },
-    "diff_head_commit_short_id": { "type": ["string", "null"] },
-    "default_merge_commit_message": { "type": ["string", "null"] },
-    "pipeline": { "type": ["object", "null"] },
-    "merge_pipeline": { "type": ["object", "null"] },
-    "work_in_progress": { "type": "boolean" },
-    "source_branch_exists": { "type": "boolean" },
-    "mergeable_discussions_state": { "type": "boolean" },
-    "conflicts_can_be_resolved_in_ui": { "type": "boolean" },
-    "branch_missing": { "type": "boolean" },
-    "commits_count": { "type": ["integer", "null"] },
-    "has_conflicts": { "type": "boolean" },
-    "can_be_merged": { "type": "boolean" },
-    "mergeable": { "type": "boolean" },
-    "project_archived": { "type": "boolean" },
-    "only_allow_merge_if_pipeline_succeeds": { "type": "boolean" },
-    "has_ci": { "type": "boolean" },
-    "ci_status": { "type": ["string", "null"] },
-    "issues_links": {
-      "type": "object",
-      "required": ["closing", "mentioned_but_not_closing", "assign_to_closing"],
+  "allOf": [
+    { "$ref": "merge_request_poll_cached_widget.json" },
+    { "$ref": "merge_request_poll_widget.json" },
+    {
       "properties" : {
-        "closing": { "type": "string" },
-        "mentioned_but_not_closing": { "type": "string" },
-        "assign_to_closing": { "type": ["string", "null"] }
-      },
-      "additionalProperties": false
-    },
-    "source_branch_with_namespace_link": { "type": "string" },
-    "current_user": {
-      "type": "object",
-      "required": [
-        "can_remove_source_branch",
-        "can_revert_on_current_merge_request",
-        "can_cherry_pick_on_current_merge_request"
-      ],
-      "properties": {
-        "can_remove_source_branch": { "type": "boolean" },
-        "can_revert_on_current_merge_request": { "type": ["boolean", "null"] },
-        "can_cherry_pick_on_current_merge_request": { "type": ["boolean", "null"] },
-        "can_create_note": { "type": "boolean" },
-        "can_create_issue": { "type": "boolean" },
-        "can_update": { "type": "boolean" }
-      },
-      "additionalProperties": false
-    },
-    "target_branch_commits_path": { "type": "string" },
-    "target_branch_tree_path": { "type": "string" },
-    "source_branch_path": { "type": "string" },
-    "conflict_resolution_path": { "type": ["string", "null"] },
-    "cancel_merge_when_pipeline_succeeds_path": { "type": ["string", "null"] },
-    "create_issue_to_resolve_discussions_path": { "type": ["string", "null"] },
-    "merge_path": { "type": ["string", "null"] },
-    "cherry_pick_in_fork_path": { "type": ["string", "null"] },
-    "revert_in_fork_path": { "type": ["string", "null"] },
-    "email_patches_path": { "type": "string" },
-    "plain_diff_path": { "type": "string" },
-    "merge_request_basic_path": { "type": "string" },
-    "merge_request_widget_path": { "type": "string" },
-    "new_blob_path": { "type": ["string", "null"] },
-    "merge_check_path": { "type": "string" },
-    "ci_environments_status_path": { "type": "string" },
-    "default_merge_commit_message_with_description": { "type": "string" },
-    "default_squash_commit_message": { "type": "string" },
-    "commits_without_merge_commits": { "type": "array" },
-    "diverged_commits_count": { "type": "integer" },
-    "commit_change_content_path": { "type": "string" },
-    "merge_commit_path": { "type": ["string", "null"] },
-    "remove_wip_path": { "type": ["string", "null"] },
-    "commits_count": { "type": "integer" },
-    "remove_source_branch": { "type": ["boolean", "null"] },
-    "merge_ongoing": { "type": "boolean" },
-    "ff_only_enabled": { "type": ["boolean", false] },
-    "should_be_rebased": { "type": "boolean" },
-    "create_note_path": { "type": ["string", "null"] },
-    "preview_note_path": { "type": ["string", "null"] },
-    "rebase_commit_sha": { "type": ["string", "null"] },
-    "rebase_in_progress": { "type": "boolean" },
-    "can_push_to_source_branch": { "type": "boolean" },
-    "rebase_path": { "type": ["string", "null"] },
-    "squash": { "type": "boolean" },
-    "test_reports_path": { "type": ["string", "null"] },
-    "can_receive_suggestion": { "type": "boolean" },
-    "source_branch_protected": { "type": "boolean" },
-    "conflicts_docs_path": { "type": ["string", "null"] },
-    "merge_request_pipelines_docs_path": { "type": ["string", "null"] }
-  }
+        "merge_params": { "type": ["object", "null"] },
+        "source_project_full_path": { "type": ["string", "null"]},
+        "target_project_full_path": { "type": ["string", "null"]},
+        "email_patches_path": { "type": "string" },
+        "plain_diff_path": { "type": "string" },
+        "merge_request_basic_path": { "type": "string" },
+        "merge_request_widget_path": { "type": "string" },
+        "merge_request_cached_widget_path": { "type": "string" },
+        "create_note_path": { "type": ["string", "null"] },
+        "commit_change_content_path": { "type": "string" },
+        "preview_note_path": { "type": ["string", "null"] },
+        "conflicts_docs_path": { "type": ["string", "null"] },
+        "merge_request_pipelines_docs_path": { "type": ["string", "null"] },
+        "ci_environments_status_path": { "type": "string" },
+        "issues_links": {
+          "type": "object",
+          "required": ["closing", "mentioned_but_not_closing", "assign_to_closing"],
+          "properties" : {
+            "closing": { "type": "string" },
+            "mentioned_but_not_closing": { "type": "string" },
+            "assign_to_closing": { "type": ["string", "null"] }
+          },
+          "additionalProperties": false
+        }
+      }
+    }
+  ]
 }
diff --git a/spec/models/merge_request_spec.rb b/spec/models/merge_request_spec.rb
index 6a5bd276233..53424204db7 100644
--- a/spec/models/merge_request_spec.rb
+++ b/spec/models/merge_request_spec.rb
@@ -1988,6 +1988,7 @@ describe MergeRequest do
       params = {}
       merge_jid = 'hash-123'
 
+      expect(merge_request).to receive(:expire_etag_cache)
       expect(MergeWorker).to receive(:perform_async).with(merge_request.id, user_id, params) do
         merge_jid
       end
@@ -2011,6 +2012,7 @@ describe MergeRequest do
         .with(merge_request.id, user_id)
         .and_return(rebase_jid)
 
+      expect(merge_request).to receive(:expire_etag_cache)
       expect(merge_request).to receive(:lock!).and_call_original
 
       execute