Don't store host to stay stateless

openfisca_web_api_preview/app.py

@@ -59,20 +59,12 @@ def create_app(tax_benefit_system,
 
     data = build_data(tax_benefit_system)
 
-    def resolve_host(request):
-        if data['host'] is not None:
-            return data['host']
-        host = request.host_url
-        data['host'] = host
-        data['openAPI_spec']['host'] = host
-        return host
-
     DEFAULT_WELCOME_MESSAGE = "This is the root of an OpenFisca Web API. To learn how to use it, check the general documentation (https://openfisca.org/doc/api) and the OpenAPI specification of this instance ({}spec)."
 
     @app.route('/')
     def get_root():
         return jsonify({
-            'welcome': welcome_message or DEFAULT_WELCOME_MESSAGE.format(resolve_host(request))
+            'welcome': welcome_message or DEFAULT_WELCOME_MESSAGE.format(request.host_url)
             }), 300
 
     @app.route('/parameters')
@@ -103,9 +95,15 @@ def get_variable(id):
 
     @app.route('/spec')
     def get_spec():
-        if data['host'] is None:
-            resolve_host(request)
-        return jsonify(data['openAPI_spec'])
+
+        # Ugly Python2-compatible way
+        response = {}
+        response.update(data['openAPI_spec'])
+        response.update({'host': request.host_url})
+        return jsonify(response)
+
+        # Nice Python3 syntax, but doesn't work in Python 2
+        # return jsonify({**data['openAPI_spec'], **{'host': request.host_url}})
 
     def handle_invalid_json(error):
         json_response = jsonify({

openfisca_web_api_preview/loader/__init__.py

@@ -26,5 +26,5 @@ def build_data(tax_benefit_system):
         'parameters_description': extract_description(parameters),
         'variables': variables,
         'variables_description': extract_description(variables),
-        'host': None  # Will be set at first request
+        'host': None  # Will be set by mirroring requests
         }