fix back-reference of dynamically created route for service by pyramihook

[fmigneault]

Using config.route_prefix and the add_cornice_service directive, I am able to register services that are used as decorators on pyramid view functions, with the appropriate prefix applied. So far, everything is ok.

However, I am also using at the same time the https://github.com/Cornices/cornice.ext.swagger package, with the help of multiple extended definitions/converters in https://github.com/crim-ca/weaver/blob/master/weaver/wps_restapi/colander_extras.py + Cornices/cornice.ext.swagger@main...fmigneault:cornice.ext.swagger:openapi-3, to auto-generate the OpenAPI 3.x definition represented by all the service paths, bodies, responses, etc. (relates to Cornices/cornice.ext.swagger#133).

When running the Swagger/OpenAPI generator, the service paths are resolved using the Service.path property. Since the services are configured with the non-prefixed path, and that prefixes are applied on the fly by add_cornice_service, I end up with incorrect paths whenever config.route_prefix is set to anything. Looking deeper into the cornice-swagger code (i.e.: https://github.com/Cornices/cornice.ext.swagger/blob/609f923784d935ba5f497e9ebb87b8e5a21747a6/src/cornice_swagger/swagger.py#L571-L593), I find that the route-builder looks for Service.pyramid_route instead of using Service.path if it is defined, in case it could extract a predefined route (aka the name definition referenced by config.add_route).

Similarly, the pyramid add_cornice_service directive looks for that Service.pyramid_route in case it already exists to use it:

cornice/src/cornice/pyramidhook.py

Lines 169 to 183 in 677aa40

	def register_service_views(config, service):
	"""Register the routes of the given service into the pyramid router.
	:param config: the pyramid configuration object that will be populated.
	:param service: the service object containing the definitions
	"""
	route_name = service.name
	existing_route = service.pyramid_route
	prefix = config.route_prefix or ""
	services = config.registry.cornice_services
	if existing_route:
	route_name = existing_route
	services["__cornice" + existing_route] = service
	else:
	services[prefix + service.path] = service

Now, the issue is that, when using add_cornice_service WITHOUT a predefined route, it creates one dynamically, but does not back-propagate this route reference onto the service. In order words, services[prefix + service.path] = service is set with the appropriate prefix, but the linked service in that dictionary still only has the Service.path reference without prefix.

This PR applies the route_name that is expected to be created just a few lines after onto the service.pyramid_route property.
This way, cornice-swagger is able to correctly resolve the prefixed path of the service.

cornice/src/cornice/pyramidhook.py

Lines 224 to 226 in 677aa40

	# register route when not using exiting pyramid routes
	if not existing_route:
	config.add_route(route_name, service.path, **route_args)

[fmigneault]

@leplatrem FYI

[leplatrem]

Thanks @fmigneault for this detailed explanation, it looks like you went deep into the implementation.

I haven't touched this code base for a long time, and I'm wondering whether this change could have side-effects. I believe that Cornice users appreciate the very low level of activity and thus high stability. And I wouldn't want to disturb that :)
Excuse me if this sounds stupid, but wouldn't it be safer to fix cornice swagger?

If you are sure about the approach, would you mind adding a unit test to reproduce the issue you describe?

Thank you, hope that you understand my "conservatism" :)

[fmigneault]

Unfortunately, the CorniceSwagger.service references are obtained from cornice.service.get_services(). It is a List[cornice.service.Service], so the prefix + service.path used as dict key in register_service_views are not making their way to the step inferring the API paths in CorniceSwagger. I think it would need important refactors to make it work from the cornice-swagger side.

Since the condition if not existing_route creates the route a bit later, I would be surprised that setting service.pyramid_route would have a side effect in this case, since it basically sets the value in the same way as if the route was provided explicitly in advance. I couldn't find any other place where service.pyramid_route is used then inside register_service_views.

[fmigneault]

Well, I think I have found one uncommon side-effect with the proposed change after all.

When running a test suite with webtest for example, that employs multiple webtest.TestApp instances created for different combinations of pyramid configurations, the fact that service.pyramid_route = route_name gets defined can lead to a situation were the add_route is called only the first time the configuration went over config.add_cornice_service, but any subsequent webtest application re-including the configuration will raise a "not route named ...". This is due to a test suite using the same imported modules and cornice.Service definitions remaining in memory between test suites. Therefore, the route does not get recreated because service.pyramid_route precheck thinks it was already defined.

I have tried calling cornice.service.clear_services() before recreating the config, but that doesn't seem to be enough. The services remain in memory somewhere.

Do you have any idea how this kind of problem could be resolved?