1 files changed, 126 insertions, 0 deletions
diff --git a/lib/gitlab/asciidoc/include_processor.rb b/lib/gitlab/asciidoc/include_processor.rb
new file mode 100644
index 00000000000..c6fbf540e9c
--- /dev/null
+++ b/lib/gitlab/asciidoc/include_processor.rb
@@ -0,0 +1,126 @@
+# frozen_string_literal: true
+
+require 'asciidoctor/include_ext/include_processor'
+
+module Gitlab
+  module Asciidoc
+    # Asciidoctor extension for processing includes (macro include::[]) within
+    # documents inside the same repository.
+    class IncludeProcessor < Asciidoctor::IncludeExt::IncludeProcessor
+      extend ::Gitlab::Utils::Override
+
+      def initialize(context)
+        super(logger: Gitlab::AppLogger)
+
+        @context = context
+        @repository = context[:project].try(:repository)
+
+        # Note: Asciidoctor calls #freeze on extensions, so we can't set new
+        # instance variables after initialization.
+        @cache = {
+            uri_types: {}
+        }
+      end
+
+      protected
+
+      override :include_allowed?
+      def include_allowed?(target, reader)
+        doc = reader.document
+
+        return false if doc.attributes.fetch('max-include-depth').to_i < 1
+        return false if target_uri?(target)
+
+        true
+      end
+
+      override :resolve_target_path
+      def resolve_target_path(target, reader)
+        return unless repository.try(:exists?)
+
+        base_path = reader.include_stack.empty? ? requested_path : reader.file
+        path = resolve_relative_path(target, base_path)
+
+        path if Gitlab::Git::Blob.find(repository, ref, path)
+      end
+
+      override :read_lines
+      def read_lines(filename, selector)
+        blob = read_blob(ref, filename)
+
+        if selector
+          blob.data.each_line.select.with_index(1, &selector)
+        else
+          blob.data
+        end
+      end
+
+      override :unresolved_include!
+      def unresolved_include!(target, reader)
+        reader.unshift_line("*[ERROR: include::#{target}[] - unresolved directive]*")
+      end
+
+      private
+
+      attr_accessor :context, :repository, :cache
+
+      # Gets a Blob at a path for a specific revision.
+      # This method will check that the Blob exists and contains readable text.
+      #
+      # revision - The String SHA1.
+      # path     - The String file path.
+      #
+      # Returns a Blob
+      def read_blob(ref, filename)
+        blob = repository&.blob_at(ref, filename)
+
+        raise 'Blob not found' unless blob
+        raise 'File is not readable' unless blob.readable_text?
+
+        blob
+      end
+
+      # Resolves the given relative path of file in repository into canonical
+      # path based on the specified base_path.
+      #
+      # Examples:
+      #
+      #   # File in the same directory as the current path
+      #   resolve_relative_path("users.adoc", "doc/api/README.adoc")
+      #   # => "doc/api/users.adoc"
+      #
+      #   # File in the same directory, which is also the current path
+      #   resolve_relative_path("users.adoc", "doc/api")
+      #   # => "doc/api/users.adoc"
+      #
+      #   # Going up one level to a different directory
+      #   resolve_relative_path("../update/7.14-to-8.0.adoc", "doc/api/README.adoc")
+      #   # => "doc/update/7.14-to-8.0.adoc"
+      #
+      # Returns a String
+      def resolve_relative_path(path, base_path)
+        p = Pathname(base_path)
+        p = p.dirname unless p.extname.empty?
+        p += path
+
+        p.cleanpath.to_s
+      end
+
+      def current_commit
+        cache[:current_commit] ||= context[:commit] || repository&.commit(ref)
+      end
+
+      def ref
+        context[:ref] || context[:project].default_branch
+      end
+
+      def requested_path
+        cache[:requested_path] ||= Addressable::URI.unescape(context[:requested_path])
+      end
+
+      def uri_type(path)
+        cache[:uri_types][path] ||= current_commit&.uri_type(path)
+      end
+    end
+  end
+end