Fix proposal presenter #author method for private user proposals

app/presenters/concerns/decidim/privacy/proposal_presenter_extensions.rb

@@ -0,0 +1,20 @@
+# frozen_string_literal: true
+
+module Decidim
+  module Privacy
+    module ProposalPresenterExtensions
+      extend ActiveSupport::Concern
+
+      included do
+        def author
+          @author ||= if official?
+                        Decidim::Proposals::OfficialAuthorPresenter.new
+                      else
+                        coauthorship = coauthorships.includes(:author, :user_group).first
+                        coauthorship.user_group&.presenter || coauthorship.author&.presenter
+                      end
+        end
+      end
+    end
+  end
+end

lib/decidim/privacy/engine.rb

@@ -224,6 +224,9 @@ class Engine < ::Rails::Engine
             Decidim::Proposals::Permissions.include(
               Decidim::Privacy::PermissionsExtensions
             )
+
+            # presenters
+            Decidim::Proposals::ProposalPresenter.include(Decidim::Privacy::ProposalPresenterExtensions)
           end
 
           if Decidim.module_installed? :comments

spec/presenters/decidim/proposals/proposal_presenter_spec.rb

@@ -0,0 +1,18 @@
+# frozen_string_literal: true
+
+require "spec_helper"
+
+describe Decidim::Proposals::ProposalPresenter, type: :helper do
+  let(:component) { create(:proposal_component) }
+  let(:proposal) { create(:proposal, component: component, users: [author]) }
+  let(:author) { create(:user, :confirmed, organization: component.organization) }
+  let(:presenter) { described_class.new(proposal) }
+
+  describe "#author" do
+    subject { presenter.author }
+
+    context "when the author is private (default)" do
+      it { is_expected.to be_nil }
+    end
+  end
+end