Support Markdown rendering using multiple projects

This refactors the Markdown pipeline so it supports the rendering of
multiple documents that may belong to different projects. An example of
where this happens is when displaying the event feed of a group. In this
case we retrieve events for all projects in the group. Previously we
would group events per project and render these chunks separately, but
this would result in many SQL queries being executed. By extending the
Markdown pipeline to support this out of the box we can drastically
reduce the number of SQL queries.

To achieve this we introduce a new object to the pipeline:
Banzai::RenderContext. This object simply wraps two other objects: an
optional Project instance, and an optional User instance. On its own
this wouldn't be very helpful, but a RenderContext can also be used to
associate HTML documents with specific Project instances. This work is
done in Banzai::ObjectRenderer and allows us to reuse as many queries
(and results) as possible.

10 files changed, 25 insertions, 11 deletions

diff --git a/spec/lib/banzai/reference_parser/base_parser_spec.rb b/spec/lib/banzai/reference_parser/base_parser_spec.rb
index 6175d4c4ca9..4e6e8eca38a 100644
--- a/spec/lib/banzai/reference_parser/base_parser_spec.rb
+++ b/spec/lib/banzai/reference_parser/base_parser_spec.rb
@@ -5,13 +5,14 @@ describe Banzai::ReferenceParser::BaseParser do
 
   let(:user) { create(:user) }
   let(:project) { create(:project, :public) }
+  let(:context) { Banzai::RenderContext.new(project, user) }
 
   subject do
     klass = Class.new(described_class) do
       self.reference_type = :foo
     end
 
-    klass.new(project, user)
+    klass.new(context)
   end
 
   describe '.reference_type=' do
@@ -23,6 +24,19 @@ describe Banzai::ReferenceParser::BaseParser do
     end
   end
 
+  describe '#project_for_node' do
+    it 'returns the Project for a node' do
+      document = instance_double('document', fragment?: false)
+      project = instance_double('project')
+      object = instance_double('object', project: project)
+      node = instance_double('node', document: document)
+
+      context.associate_document(document, object)
+
+      expect(subject.project_for_node(node)).to eq(project)
+    end
+  end
+
   describe '#nodes_visible_to_user' do
     let(:link) { empty_html_link }
 
@@ -164,7 +178,7 @@ describe Banzai::ReferenceParser::BaseParser do
         self.reference_type = :test
       end
 
-      instance = dummy.new(project, user)
+      instance = dummy.new(Banzai::RenderContext.new(project, user))
       document = Nokogiri::HTML.fragment('<a class="gfm"></a><a class="gfm" data-reference-type="test"></a>')
 
       expect(instance).to receive(:gather_references)
diff --git a/spec/lib/banzai/reference_parser/commit_parser_spec.rb b/spec/lib/banzai/reference_parser/commit_parser_spec.rb
index 3505659c2c3..cca53a8b9b9 100644
--- a/spec/lib/banzai/reference_parser/commit_parser_spec.rb
+++ b/spec/lib/banzai/reference_parser/commit_parser_spec.rb
@@ -5,7 +5,7 @@ describe Banzai::ReferenceParser::CommitParser do
 
   let(:project) { create(:project, :public) }
   let(:user) { create(:user) }
-  subject { described_class.new(project, user) }
+  subject { described_class.new(Banzai::RenderContext.new(project, user)) }
   let(:link) { empty_html_link }
 
   describe '#nodes_visible_to_user' do
diff --git a/spec/lib/banzai/reference_parser/commit_range_parser_spec.rb b/spec/lib/banzai/reference_parser/commit_range_parser_spec.rb
index 21813177deb..23e16fe0213 100644
--- a/spec/lib/banzai/reference_parser/commit_range_parser_spec.rb
+++ b/spec/lib/banzai/reference_parser/commit_range_parser_spec.rb
@@ -5,7 +5,7 @@ describe Banzai::ReferenceParser::CommitRangeParser do
 
   let(:project) { create(:project, :public) }
   let(:user) { create(:user) }
-  subject { described_class.new(project, user) }
+  subject { described_class.new(Banzai::RenderContext.new(project, user)) }
   let(:link) { empty_html_link }
 
   describe '#nodes_visible_to_user' do
diff --git a/spec/lib/banzai/reference_parser/external_issue_parser_spec.rb b/spec/lib/banzai/reference_parser/external_issue_parser_spec.rb
index 25969b65168..1cb31e57114 100644
--- a/spec/lib/banzai/reference_parser/external_issue_parser_spec.rb
+++ b/spec/lib/banzai/reference_parser/external_issue_parser_spec.rb
@@ -5,7 +5,7 @@ describe Banzai::ReferenceParser::ExternalIssueParser do
 
   let(:project) { create(:project, :public) }
   let(:user) { create(:user) }
-  subject { described_class.new(project, user) }
+  subject { described_class.new(Banzai::RenderContext.new(project, user)) }
   let(:link) { empty_html_link }
 
   describe '#nodes_visible_to_user' do
diff --git a/spec/lib/banzai/reference_parser/issue_parser_spec.rb b/spec/lib/banzai/reference_parser/issue_parser_spec.rb
index cb7f8b20dda..77c2064caba 100644
--- a/spec/lib/banzai/reference_parser/issue_parser_spec.rb
+++ b/spec/lib/banzai/reference_parser/issue_parser_spec.rb
@@ -7,7 +7,7 @@ describe Banzai::ReferenceParser::IssueParser do
   let(:user)    { create(:user) }
   let(:issue)   { create(:issue, project: project) }
   let(:link)    { empty_html_link }
-  subject       { described_class.new(project, user) }
+  subject       { described_class.new(Banzai::RenderContext.new(project, user)) }
 
   describe '#nodes_visible_to_user' do
     context 'when the link has a data-issue attribute' do
diff --git a/spec/lib/banzai/reference_parser/label_parser_spec.rb b/spec/lib/banzai/reference_parser/label_parser_spec.rb
index b700161d6c2..e4df2533821 100644
--- a/spec/lib/banzai/reference_parser/label_parser_spec.rb
+++ b/spec/lib/banzai/reference_parser/label_parser_spec.rb
@@ -6,7 +6,7 @@ describe Banzai::ReferenceParser::LabelParser do
   let(:project) { create(:project, :public) }
   let(:user) { create(:user) }
   let(:label) { create(:label, project: project) }
-  subject { described_class.new(project, user) }
+  subject { described_class.new(Banzai::RenderContext.new(project, user)) }
   let(:link) { empty_html_link }
 
   describe '#nodes_visible_to_user' do
diff --git a/spec/lib/banzai/reference_parser/merge_request_parser_spec.rb b/spec/lib/banzai/reference_parser/merge_request_parser_spec.rb
index 14542342cf6..5417b1f00be 100644
--- a/spec/lib/banzai/reference_parser/merge_request_parser_spec.rb
+++ b/spec/lib/banzai/reference_parser/merge_request_parser_spec.rb
@@ -6,7 +6,7 @@ describe Banzai::ReferenceParser::MergeRequestParser do
   let(:user) { create(:user) }
   let(:project) { create(:project, :public) }
   let(:merge_request) { create(:merge_request, source_project: project) }
-  subject { described_class.new(project, user) }
+  subject { described_class.new(Banzai::RenderContext.new(merge_request.target_project, user)) }
   let(:link) { empty_html_link }
 
   describe '#nodes_visible_to_user' do
diff --git a/spec/lib/banzai/reference_parser/milestone_parser_spec.rb b/spec/lib/banzai/reference_parser/milestone_parser_spec.rb
index 7dacdf8d629..751d042ffde 100644
--- a/spec/lib/banzai/reference_parser/milestone_parser_spec.rb
+++ b/spec/lib/banzai/reference_parser/milestone_parser_spec.rb
@@ -6,7 +6,7 @@ describe Banzai::ReferenceParser::MilestoneParser do
   let(:project) { create(:project, :public) }
   let(:user) { create(:user) }
   let(:milestone) { create(:milestone, project: project) }
-  subject { described_class.new(project, user) }
+  subject { described_class.new(Banzai::RenderContext.new(project, user)) }
   let(:link) { empty_html_link }
 
   describe '#nodes_visible_to_user' do
diff --git a/spec/lib/banzai/reference_parser/snippet_parser_spec.rb b/spec/lib/banzai/reference_parser/snippet_parser_spec.rb
index 69ec3f66aa8..d410bd4c164 100644
--- a/spec/lib/banzai/reference_parser/snippet_parser_spec.rb
+++ b/spec/lib/banzai/reference_parser/snippet_parser_spec.rb
@@ -9,7 +9,7 @@ describe Banzai::ReferenceParser::SnippetParser do
   let(:external_user) { create(:user, :external) }
   let(:project_member) { create(:user) }
 
-  subject { described_class.new(project, user) }
+  subject { described_class.new(Banzai::RenderContext.new(project, user)) }
   let(:link) { empty_html_link }
 
   def visible_references(snippet_visibility, user = nil)
diff --git a/spec/lib/banzai/reference_parser/user_parser_spec.rb b/spec/lib/banzai/reference_parser/user_parser_spec.rb
index b079a3be029..112447f098e 100644
--- a/spec/lib/banzai/reference_parser/user_parser_spec.rb
+++ b/spec/lib/banzai/reference_parser/user_parser_spec.rb
@@ -6,7 +6,7 @@ describe Banzai::ReferenceParser::UserParser do
   let(:group) { create(:group) }
   let(:user) { create(:user) }
   let(:project) { create(:project, :public, group: group, creator: user) }
-  subject { described_class.new(project, user) }
+  subject { described_class.new(Banzai::RenderContext.new(project, user)) }
   let(:link) { empty_html_link }
 
   describe '#referenced_by' do