Friday, May 18, 2018

Diving into Lino’s URL design

I opened #2392 : Lino’s URL design has grown historically, it is full of dragons, poorly documented, based on the ExtJS way of doing things, and probably a full chaos.

Here is the code (from lino.modlib.extjs.Plugin ) that defines Lino’s URL patterns:

urlpatterns = [
    url(rx + '$', views.AdminIndex.as_view()),
    url(rx + r'api/main_html$', views.MainHtml.as_view()),
    url(rx + r'grid_config/(?P<app_label>\w+)/(?P<actor>\w+)$',
    url(rx + r'api/(?P<app_label>\w+)/(?P<actor>\w+)$',
    url(rx + r'api/(?P<app_label>\w+)/(?P<actor>\w+)/(?P<pk>.+)$',
    url(rx + r'restful/(?P<app_label>\w+)/(?P<actor>\w+)$',
    url(rx + r'restful/(?P<app_label>\w+)/(?P<actor>\w+)/(?P<pk>.+)$',
    url(rx + r'choices/(?P<app_label>\w+)/(?P<rptname>\w+)$',
    url(rx + r'choices/(?P<app_label>\w+)/(?P<rptname>\w+)/'
    url(rx + r'apchoices/(?P<app_label>\w+)/(?P<actor>\w+)/'
    # the thread_id can be a negative number:
    url(rx + r'callbacks/(?P<thread_id>[\-0-9a-zA-Z]+)/'

Summary of above code in English:

  • / returns the index page which does an AJAX call to /api/main_html.
  • /api/main_html returns the dashboard or more precisely the “inner html” to be rendered in the body of the main window.
  • /api/app_label/actor_name and /api/app_label/actor_name/pk do almost everything.
  • /restful/app_label/actor_name and /restful/app_label/actor_name/pk are like /api with some subtile differences. Used only by lino_xl.lib.extensible.CalendarPanel.
  • /choices/app_label/actor_name : show the choices of a foreignkey field
  • /apchoices/app_label/actor_name : same as choices but for action parameters
  • /grid_config : not used
  • /callbacks/thread_id : used by Lino’s unique action callback system.

How should a good system look like? First thoughts…

First of all make it resource-centric: every actor is a “resource”.

Actions that open a window:

  • ShowTable : GET /contacts/Persons/grid –> { “eval_js”: “Lino.contacts.Persons.open_grid(…)”}
  • ShowDetail : GET /contacts/Persons/detail?pk=1 –> { “eval_js”: “Lino.contacts.Persons.open_detail(…)”}.
  • ShowInsert : GET /contacts/Persons/insert –> { “eval_js”: “Lino.contacts.Persons.open_grid(…)”}.
  • ShowEmptyTable : GET /courses/StatusReport/show –> { “eval_js”: “…)”}.
  • ShowSlaveTable : GET /checkdata/ProblemsByOwner/show –> { “eval_js”: “…)”}.

Submit actions from a grid

  • SaveRow : PUT /contacts/Persons/grid_put –> { success:…}
  • CreateRow : POST /contacts/Persons/

Submit actions from a form

  • SubmitDetail : PUT /contacts/Persons/submit_detail –> {success:…}
  • SubmitInsert : POST /contacts/Persons/

Row actions:

  • DeleteSelected : DELETE /contacts/Persons/?sr=1

Custom actions:

  • users.AssignToMe : POST /users/User/assign_to_me?sr=1

Observation: Currently many buttons in the ExtJS interface don’t do an AJAX request, they are defined to directly call a Javascript function.

For example the Contacts ‣ Person menu item is defined with this handler:

"handler": function() {}

Or the Insert button on a grid will directly call

This approach has the advantage of reducing network traffic, but it’s not RESTful.

API change in Actor.get_actions()

I have been thinking about is_callable_from. This method should be renamed to is_available_from or sth similar to express better what it does. For example the ShowTable action (“open a grid window”) exists on all table actors, but it should not appear in the toolbar of its own grid or detail. Most toolbar actions should show both in a grid and in a detail window, but not in an insert window.

API change : Actor.get_actions() no longer has an optional argument called_from but always returns all actions. The few places where we called it with an argument must now call the new method get_button_actions.

That method now raises an exception “20180518 {} is not a windows action” because it makes no sense to ask for available buttons when you don’t specify which type of window. This exception unveiled one such nonsense call

SubmitInsert is not a window action but calls which wants to know the disabled fields, and for this it ultimately calls lino.core.dbtables.Table.make_disabled_fields(). This method now no longer disables actions when the parent is not a window action.

Miscellaneous code changes

  • I removed RedirectAction because it is not being used.

Removed some uselessly generated JS code

Side effect: I noticed that Lino generated a lot of useless functions into the lino_900_en.js file. For example this one:

Lino.contacts.Persons.grid_put = function(rp, is_main, pk, params) {
  var h = function() {
    Lino.run_row_action(rp, is_main, "/contacts/Persons", "GET", pk, "grid_put", params, null);
  var panel = Ext.getCmp(rp);
  if(panel) panel.do_when_clean(true, h); else h();

I fixed this problem by extending the test whether we need to call js_render_custom_action.

The lino_900_en.js for team had 48711 lines. After fixing the problem, it’s only 44392 lines. We saved more than 4000 useless lines of JS code.

There is more useless JS code in the lino_XXX_yy.js file : for example it generates a GridPanel and related functions for Lino.countries.PlaceTypes. This table is never used because there is no menu item for it. We might extend the code which decides whether js_render_GridPanel_class() must be called or not. The condition would be: if it is a master table but does not have any menu item. But that might be dangerous (cause uncovered regressions), so I prefer to leave this for another time.

Wrong error message when no eid card found

When a user invokes the FindByBeIdAction while there is no card in the read, Lino says “AttributeError: AttrDict instance has no key ‘national_number’ (keys are success, eidreader_version)” instead of “No card data found”.

That’s because the value of data.success in the following code is "False" (a non-empty string) and not False (a boolean):

data = load_card_data(ar.request.POST['uuid'])
data = AttrDict(data)
if not data.success:
    raise Warning(_("No card data found."))

Indeed, the test files used by lino_book.projects.adg.tests.test_beid don’t simulate exactly what happens in reality.

>>> import json
>>> d = {'eidreader_version': '0.0.8', 'success': False}
>>> json.dumps(d)
>>> data = "{'eidreader_version': '0.0.8', 'success': False}"
>>> # data = '{"success": "False", "eidreader_version": "0.0.8"}'
>>> json.loads(data)