Allow reshares with no root

docs/_entities/reshare.md

@@ -7,6 +7,10 @@ This entity represents a reshare of a [StatusMessage][status_message]. It inheri
 The recipient must [fetch][fetching] the root from `root_author` if the post is not already known.
 When the `root_guid` is already available locally, the recipient must validate that it's from `root_author`.
 
+A special case when the entity doesn't include `root_author` and `root_guid` is allowed. This case represents
+a reshare for a deleted post. If there is only one of `root_author` and `root_guid` is present, then the entity
+is not valid.
+
 ## Properties
 
 | Property      | Type                         | Description                                                   |

lib/diaspora_federation/entities/reshare.rb

@@ -31,6 +31,11 @@ module DiasporaFederation
       # Fetch and receive root post from remote, if not available locally
       # and validates if it's from the correct author
       def validate_root
+        return if root_author.nil? && root_guid.nil?
+
+        raise Entity::ValidationError, "#{self}: root_guid can't be nil if root_author is present" if root_guid.nil?
+        raise Entity::ValidationError, "#{self}: root_author can't be nil if root_guid is present" if root_author.nil?
+
         root = RelatedEntity.fetch(root_author, "Post", root_guid)
 
         return if root_author == root.author

lib/diaspora_federation/validators/reshare_validator.rb

@@ -4,9 +4,9 @@ module DiasporaFederation
     class ReshareValidator < Validation::Validator
       include Validation
 
-      rule :root_author, %i[not_empty diaspora_id]
+      rule :root_author, :diaspora_id
 
-      rule :root_guid, :guid
+      rule :root_guid, guid: {nilable: true}
 
       rule :author, %i[not_empty diaspora_id]
 

spec/lib/diaspora_federation/entities/reshare_spec.rb

@@ -74,6 +74,31 @@ XML
             Entities::Reshare.from_xml(Nokogiri::XML(xml).root)
           }.to raise_error Entity::ValidationError
         end
+
+        it "validates a reshare with no root" do
+          data[:root_author] = nil
+          data[:root_guid] = nil
+
+          reshare = Entities::Reshare.from_xml(Nokogiri::XML(xml).root)
+          expect(reshare.root_author).to be_nil
+          expect(reshare.root_guid).to be_nil
+        end
+
+        it "disallows root_author without root_guid" do
+          data[:root_guid] = nil
+
+          expect {
+            Entities::Reshare.from_xml(Nokogiri::XML(xml).root)
+          }.to raise_error Entity::ValidationError
+        end
+
+        it "disallows root_guid without root_author" do
+          data[:root_author] = nil
+
+          expect {
+            Entities::Reshare.from_xml(Nokogiri::XML(xml).root)
+          }.to raise_error Entity::ValidationError
+        end
       end
     end
   end

spec/lib/diaspora_federation/validators/reshare_validator_spec.rb

@@ -3,20 +3,29 @@ module DiasporaFederation
     let(:entity) { :reshare_entity }
     it_behaves_like "a common validator"
 
-    %i[root_author author].each do |prop|
-      describe "##{prop}" do
-        it_behaves_like "a diaspora* ID validator" do
-          let(:property) { prop }
-          let(:mandatory) { true }
-        end
+    describe "#author" do
+      it_behaves_like "a diaspora* ID validator" do
+        let(:property) { :author }
+        let(:mandatory) { true }
       end
     end
 
-    %i[root_guid guid].each do |prop|
-      describe "##{prop}" do
-        it_behaves_like "a guid validator" do
-          let(:property) { prop }
-        end
+    describe "#guid" do
+      it_behaves_like "a guid validator" do
+        let(:property) { :guid }
+      end
+    end
+
+    describe "#root_guid" do
+      it_behaves_like "a nilable guid validator" do
+        let(:property) { :root_guid }
+      end
+    end
+
+    describe "#root_author" do
+      it_behaves_like "a diaspora* ID validator" do
+        let(:property) { :root_author }
+        let(:mandatory) { false }
       end
     end
 

spec/support/shared_validator_specs.rb

@@ -92,7 +92,7 @@ shared_examples "a diaspora* ID validator" do
   end
 end
 
-shared_examples "a guid validator" do
+shared_examples "common guid validator" do
   it "validates a well-formed guid from redmatrix" do
     validator = described_class.new(entity_stub(entity, property => "1234567890ABCDefgh_ijkl-mnopQR@example.com:3000"))
 
@@ -113,6 +113,10 @@ shared_examples "a guid validator" do
     expect(validator).not_to be_valid
     expect(validator.errors).to include(property)
   end
+end
+
+shared_examples "a guid validator" do
+  include_examples "common guid validator"
 
   it "must not be nil or empty" do
     [nil, ""].each do |val|
@@ -124,6 +128,17 @@ shared_examples "a guid validator" do
   end
 end
 
+shared_examples "a nilable guid validator" do
+  include_examples "common guid validator"
+
+  it "can be nil" do
+    validator = described_class.new(entity_stub(entity, property => nil))
+
+    expect(validator).to be_valid
+    expect(validator.errors).to be_empty
+  end
+end
+
 shared_examples "a boolean validator" do
   it "validates a well-formed boolean" do
     [true, "true", false, "false"].each do |val|