Handle missing instance domain outside production (#405)

web/lib/potato_mesh/application/federation.rb

@@ -15,10 +15,25 @@
 module PotatoMesh
   module App
     module Federation
+      # Resolve the canonical domain for the running instance.
+      #
+      # @return [String, nil] sanitized instance domain or nil outside production.
+      # @raise [RuntimeError] when the domain cannot be determined in production.
       def self_instance_domain
         sanitized = sanitize_instance_domain(app_constant(:INSTANCE_DOMAIN))
         return sanitized if sanitized
 
+        unless production_environment?
+          debug_log(
+            "INSTANCE_DOMAIN unavailable; skipping self instance domain",
+            context: "federation.instances",
+            app_env: string_or_nil(ENV["APP_ENV"]),
+            rack_env: string_or_nil(ENV["RACK_ENV"]),
+            source: app_constant(:INSTANCE_DOMAIN_SOURCE),
+          )
+          return nil
+        end
+
         raise "INSTANCE_DOMAIN could not be determined"
       end
 

web/lib/potato_mesh/application/helpers.rb

@@ -334,6 +334,16 @@ module PotatoMesh
         ENV["RACK_ENV"] == "test"
       end
 
+      # Determine whether the application is running in a production environment.
+      #
+      # @return [Boolean] true when APP_ENV or RACK_ENV resolves to "production".
+      def production_environment?
+        app_env = string_or_nil(ENV["APP_ENV"])&.downcase
+        rack_env = string_or_nil(ENV["RACK_ENV"])&.downcase
+
+        app_env == "production" || rack_env == "production"
+      end
+
       # Determine whether federation features should be active.
       #
       # @return [Boolean] true when federation configuration allows it.

web/spec/app_spec.rb

@@ -813,6 +813,52 @@ RSpec.describe "Potato Mesh Sinatra app" do
       end
     end
 
+    describe ".self_instance_domain" do
+      around do |example|
+        original_app_env = ENV["APP_ENV"]
+        original_rack_env = ENV["RACK_ENV"]
+        begin
+          example.run
+        ensure
+          if original_app_env
+            ENV["APP_ENV"] = original_app_env
+          else
+            ENV.delete("APP_ENV")
+          end
+
+          if original_rack_env
+            ENV["RACK_ENV"] = original_rack_env
+          else
+            ENV.delete("RACK_ENV")
+          end
+        end
+      end
+
+      it "returns the sanitized domain when configuration is present" do
+        ENV.delete("APP_ENV")
+        stub_const("PotatoMesh::Application::INSTANCE_DOMAIN", " Example.Org ") do
+          expect(application_class.self_instance_domain).to eq("example.org")
+        end
+      end
+
+      it "returns nil when the domain is unavailable outside production" do
+        ENV["APP_ENV"] = "development"
+        stub_const("PotatoMesh::Application::INSTANCE_DOMAIN", nil) do
+          expect(application_class.self_instance_domain).to be_nil
+        end
+      end
+
+      it "raises when the domain is unavailable in production" do
+        ENV["APP_ENV"] = "production"
+        stub_const("PotatoMesh::Application::INSTANCE_DOMAIN", nil) do
+          expect { application_class.self_instance_domain }.to raise_error(
+            RuntimeError,
+            "INSTANCE_DOMAIN could not be determined",
+          )
+        end
+      end
+    end
+
     describe ".self_instance_registration_decision" do
       let(:domain) { "spec.mesh.test" }