Provide a link to existing domain block when trying to block an already-blocked domain (#10663)

* When trying to block an already-blocked domain, provide a link to the block

* Fix styling for links in flash messages

* Allow blocks to be upgraded but not downgraded

app/controllers/admin/domain_blocks_controller.rb

@@ -13,7 +13,18 @@ module Admin
       authorize :domain_block, :create?
 
       @domain_block = DomainBlock.new(resource_params)
+      existing_domain_block = resource_params[:domain].present? ? DomainBlock.find_by(domain: resource_params[:domain]) : nil
 
+      if existing_domain_block.present? && !@domain_block.stricter_than?(existing_domain_block)
+        @domain_block.save
+        flash[:alert] = I18n.t('admin.domain_blocks.existing_domain_block_html', name: existing_domain_block.domain, unblock_url: admin_domain_block_path(existing_domain_block)).html_safe # rubocop:disable Rails/OutputSafety
+        @domain_block.errors[:domain].clear
+        render :new
+      else
+        if existing_domain_block.present?
+          @domain_block = existing_domain_block
+          @domain_block.update(resource_params)
+        end
         if @domain_block.save
           DomainBlockWorker.perform_async(@domain_block.id)
           log_action :create, @domain_block
@@ -22,6 +33,7 @@ module Admin
           render :new
         end
       end
+    end
 
     def show
       authorize @domain_block, :show?

app/javascript/styles/mastodon/forms.scss

@@ -533,6 +533,17 @@ code {
     color: $error-value-color;
   }
 
+  a {
+    display: inline-block;
+    color: $darker-text-color;
+    text-decoration: none;
+
+    &:hover {
+      color: $primary-text-color;
+      text-decoration: underline;
+    }
+  }
+
   p {
     margin-bottom: 15px;
   }

app/models/domain_block.rb

@@ -29,4 +29,11 @@ class DomainBlock < ApplicationRecord
   def self.blocked?(domain)
     where(domain: domain, severity: :suspend).exists?
   end
+
+  def stricter_than?(other_block)
+    return true if suspend?
+    return false if other_block.suspend? && (silence? || noop?)
+    return false if other_block.silence? && noop?
+    (reject_media || !other_block.reject_media) && (reject_reports || !other_block.reject_reports)
+  end
 end

config/locales/en.yml

@@ -269,6 +269,7 @@ en:
       created_msg: Domain block is now being processed
       destroyed_msg: Domain block has been undone
       domain: Domain
+      existing_domain_block_html: You have already imposed stricter limits on %{name}, you need to <a href="%{unblock_url}">unblock it</a> first.
       new:
         create: Create block
         hint: The domain block will not prevent creation of account entries in the database, but will retroactively and automatically apply specific moderation methods on those accounts.

spec/controllers/admin/domain_blocks_controller_spec.rb

@@ -37,7 +37,7 @@ RSpec.describe Admin::DomainBlocksController, type: :controller do
     end
 
     it 'renders new when failed to save' do
-      Fabricate(:domain_block, domain: 'example.com')
+      Fabricate(:domain_block, domain: 'example.com', severity: 'suspend')
       allow(DomainBlockWorker).to receive(:perform_async).and_return(true)
 
       post :create, params: { domain_block: { domain: 'example.com', severity: 'silence' } }
@@ -45,6 +45,17 @@ RSpec.describe Admin::DomainBlocksController, type: :controller do
       expect(DomainBlockWorker).not_to have_received(:perform_async)
       expect(response).to render_template :new
     end
+
+    it 'allows upgrading a block' do
+      Fabricate(:domain_block, domain: 'example.com', severity: 'silence')
+      allow(DomainBlockWorker).to receive(:perform_async).and_return(true)
+
+      post :create, params: { domain_block: { domain: 'example.com', severity: 'silence', reject_media: true, reject_reports: true } }
+
+      expect(DomainBlockWorker).to have_received(:perform_async)
+      expect(flash[:notice]).to eq I18n.t('admin.domain_blocks.created_msg')
+      expect(response).to redirect_to(admin_instances_path(limited: '1'))
+    end
   end
 
   describe 'DELETE #destroy' do

spec/models/domain_block_spec.rb

@@ -36,4 +36,35 @@ RSpec.describe DomainBlock, type: :model do
       expect(DomainBlock.blocked?('domain')).to eq false
     end
   end
+
+  describe 'stricter_than?' do
+    it 'returns true if the new block has suspend severity while the old has lower severity' do
+      suspend = DomainBlock.new(domain: 'domain', severity: :suspend)
+      silence = DomainBlock.new(domain: 'domain', severity: :silence)
+      noop = DomainBlock.new(domain: 'domain', severity: :noop)
+      expect(suspend.stricter_than?(silence)).to be true
+      expect(suspend.stricter_than?(noop)).to be true
+    end
+
+    it 'returns false if the new block has lower severity than the old one' do
+      suspend = DomainBlock.new(domain: 'domain', severity: :suspend)
+      silence = DomainBlock.new(domain: 'domain', severity: :silence)
+      noop = DomainBlock.new(domain: 'domain', severity: :noop)
+      expect(silence.stricter_than?(suspend)).to be false
+      expect(noop.stricter_than?(suspend)).to be false
+      expect(noop.stricter_than?(silence)).to be false
+    end
+
+    it 'returns false if the new block does is less strict regarding reports' do
+      older = DomainBlock.new(domain: 'domain', severity: :silence, reject_reports: true)
+      newer = DomainBlock.new(domain: 'domain', severity: :silence, reject_reports: false)
+      expect(newer.stricter_than?(older)).to be false
+    end
+
+    it 'returns false if the new block does is less strict regarding media' do
+      older = DomainBlock.new(domain: 'domain', severity: :silence, reject_media: true)
+      newer = DomainBlock.new(domain: 'domain', severity: :silence, reject_media: false)
+      expect(newer.stricter_than?(older)).to be false
+    end
+  end
 end