Add indication for closed or merged issuables in GFM

Example: for issues that are closed, the links will now show '[closed]'
following the issue number. This is done as post-process after the markdown has
been loaded from the cache as the status of the issue may change between
the cache being populated and the content being displayed.

In order to avoid N+1 queries problem when rendering notes ObjectRenderer
populates the cache of referenced issuables for all notes at once,
before the post processing phase.

As a part of this change, the Banzai BaseParser#grouped_objects_for_nodes
method has been refactored to return a Hash utilising the node itself as the
key, since this was a common pattern of usage for this method.

1 files changed, 36 insertions, 0 deletions

diff --git a/lib/banzai/issuable_extractor.rb b/lib/banzai/issuable_extractor.rb
new file mode 100644
index 00000000000..c5ce360e172
--- /dev/null
+++ b/lib/banzai/issuable_extractor.rb
@@ -0,0 +1,36 @@
+module Banzai
+  # Extract references to issuables from multiple documents
+
+  # This populates RequestStore cache used in Banzai::ReferenceParser::IssueParser
+  # and Banzai::ReferenceParser::MergeRequestParser
+  # Populating the cache should happen before processing documents one-by-one
+  # so we can avoid N+1 queries problem
+
+  class IssuableExtractor
+    QUERY = %q(
+      descendant-or-self::a[contains(concat(" ", @class, " "), " gfm ")]
+      [@data-reference-type="issue" or @data-reference-type="merge_request"]
+    ).freeze
+
+    attr_reader :project, :user
+
+    def initialize(project, user)
+      @project = project
+      @user = user
+    end
+
+    # Returns Hash in the form { node => issuable_instance }
+    def extract(documents)
+      nodes = documents.flat_map do |document|
+        document.xpath(QUERY)
+      end
+
+      issue_parser = Banzai::ReferenceParser::IssueParser.new(project, user)
+      merge_request_parser = Banzai::ReferenceParser::MergeRequestParser.new(project, user)
+
+      issue_parser.issues_for_nodes(nodes).merge(
+        merge_request_parser.merge_requests_for_nodes(nodes)
+      )
+    end
+  end
+end