Topic/default/rql schema holder

Add two views that can serve the schema or it hash to a cwclientlib client.

The schema and the hash are stored in a cached property for optimisation.

cubicweb_rqlcontroller/views.py

@@ -33,6 +33,7 @@ from cubicweb.web import RemoteCallFailed, DirectResponse
 from cubicweb.web.controller import Controller
 from cubicweb.web.views.urlrewrite import rgx_action, SchemaBasedRewriter
 from cubicweb import Binary
+from cubicweb_rqlcontroller.rql_schema_holder import RqlIOSchemaHolder
 
 
 ARGRE = re.compile(r'__r(?P<ref>\d+)$')
@@ -74,6 +75,28 @@ class match_request_content_type(ExpectedValuePredicate):
         return header
 
 
+class RqlIOSchemaController(Controller, RqlIOSchemaHolder):
+    __regid__ = 'rqlio_schema'
+    __select__ = match_http_method('GET')
+
+    def publish(self, rset=None):
+        self._cw.set_content_type('application/json')
+        return json.dumps(
+            self.get_schema
+        ).encode(self._cw.encoding)
+
+
+class RqlIOHashController(Controller, RqlIOSchemaHolder):
+    __regid__ = 'rqlio_schema_hash'
+    __select__ = match_http_method('GET')
+
+    def publish(self, rset=None):
+        self._cw.set_content_type('application/json')
+        return json.dumps(
+            self.get_schema_hash
+        ).encode(self._cw.encoding)
+
+
 class RqlIOController(Controller):
     """posted rql queries and arguments use the following pattern:
 
@@ -167,6 +190,10 @@ class RqlIOController(Controller):
 
 class RQLIORewriter(SchemaBasedRewriter):
     rules = [
+        (re.compile('/rqlio/schema'),
+         rgx_action(controller='rqlio_schema')),
+        (re.compile('/rqlio/hash'),
+         rgx_action(controller='rqlio_schema_hash')),
         (re.compile('/rqlio/(?P<version>.+)$'),
-         rgx_action(controller='rqlio', formgroups=('version',))),
+         rgx_action(controller='rqlio', formgroups=('version',)))
     ]

[Fabien Amarger]

I would like an information about "schema" in this route. Something like

-        (re.compile('/rqlio/hash'),
+        (re.compile('/rqlio/schema/hash'),

Because for now we do not know from what this hash come.

[Frank Bessou]

I propose to not add a different route and add a header to the /rqlio/schema response:

ETag: <schema hash>

If we need to get the hash without transferring the schema, we could then use a HEAD request.

[Fabien Amarger]

That a marvellous idea! :D +1 !