Consider the current tenant in email URLs

app/mailers/application_mailer.rb

@@ -6,7 +6,25 @@ class ApplicationMailer < ActionMailer::Base
   layout "mailer"
   before_action :set_asset_host
 
+  def default_url_options
+    if Tenant.default?
+      super
+    else
+      super.merge(host: host_with_subdomain_for(super[:host]))
+    end
+  end
+
   def set_asset_host
     self.asset_host ||= root_url.delete_suffix("/")
   end
+
+  private
+
+    def host_with_subdomain_for(host)
+      if host == "localhost"
+        "#{Tenant.current_schema}.lvh.me"
+      else
+        "#{Tenant.current_schema}.#{host}"
+      end
+    end
 end

app/models/tenant.rb

@@ -31,6 +31,14 @@ class Tenant < ApplicationRecord
     ActionMailer::Base.default_url_options[:host]
   end
 
+  def self.current_schema
+    Apartment::Tenant.current
+  end
+
+  def self.default?
+    current_schema == "public"
+  end
+
   def self.switch(...)
     Apartment::Tenant.switch(...)
   end

spec/mailers/application_mailer_spec.rb

@@ -1,6 +1,28 @@
 require "rails_helper"
 
 describe ApplicationMailer do
+  describe "#default_url_options" do
+    it "returns the same options on the default tenant" do
+      allow(ActionMailer::Base).to receive(:default_url_options).and_return({ host: "consul.dev" })
+
+      expect(ApplicationMailer.new.default_url_options).to eq({ host: "consul.dev" })
+    end
+
+    it "returns the host with a subdomain on other tenants" do
+      allow(ActionMailer::Base).to receive(:default_url_options).and_return({ host: "consul.dev" })
+      allow(Tenant).to receive(:current_schema).and_return("my")
+
+      expect(ApplicationMailer.new.default_url_options).to eq({ host: "my.consul.dev" })
+    end
+
+    it "uses lvh.me for subdomains when the host is localhost" do
+      allow(ActionMailer::Base).to receive(:default_url_options).and_return({ host: "localhost", port: 3000 })
+      allow(Tenant).to receive(:current_schema).and_return("dev")
+
+      expect(ApplicationMailer.new.default_url_options).to eq({ host: "dev.lvh.me", port: 3000 })
+    end
+  end
+
   describe "#set_asset_host" do
     let(:mailer) { ApplicationMailer.new }
 
@@ -24,6 +46,24 @@ describe ApplicationMailer do
       expect(mailer.asset_host).to eq "https://localhost:3000"
     end
 
+    it "returns the host with a subdomain on other tenants" do
+      allow(ActionMailer::Base).to receive(:default_url_options).and_return(host: "consul.dev")
+      allow(Tenant).to receive(:current_schema).and_return("my")
+
+      mailer.set_asset_host
+
+      expect(mailer.asset_host).to eq "http://my.consul.dev"
+    end
+
+    it "uses lvh.me for subdomains when the host is localhost" do
+      allow(ActionMailer::Base).to receive(:default_url_options).and_return(host: "localhost", port: 3000)
+      allow(Tenant).to receive(:current_schema).and_return("dev")
+
+      mailer.set_asset_host
+
+      expect(mailer.asset_host).to eq "http://dev.lvh.me:3000"
+    end
+
     it "returns the asset host when set manually" do
       default_asset_host = ActionMailer::Base.asset_host