Lazy evaluation of RecordList[...] slicing

Author: florentx

CHANGES.rst

@@ -17,6 +17,11 @@ Changelog
   are read or methods are called.  It will use `search_read` API method
   when it's adequate.
 
+* New: extracting a part of a lazy :class:`RecordList` will not call
+  API method, for simple use cases like
+  ``env['account.move'].search([])[10:90]``.  It will set
+  ``offset`` and ``limit`` on the prepared search instead.
+
 * Retrieve models when user does not have access to ``ir.model``.
   Only for Odoo 15 there's no workaround.  For Odoo >= 16 a
   method ``get_available_models`` is available to all users.

odooly.py

@@ -2162,6 +2162,26 @@ def fetch(self):
         """Execute prepared search query."""
         return (self.id or True) and self
 
+    def __getitem__(self, key):
+        if 'id' in self.__dict__ or (getattr(key, 'start', -1) or 0) < 0:
+            return super().__getitem__(key)
+        is_stop_positive = key.stop is not None and key.stop >= 0
+        search_args = {**self._search_args}
+        new_offset, new_stop = key.start or 0, search_args.get('limit', None)
+        if is_stop_positive:
+            new_stop = key.stop if new_stop is None else min(new_stop, key.stop)
+        if new_stop is not None:
+            search_args['limit'] = limit = new_stop - new_offset
+            if limit <= 0:
+                return RecordList(self._model, [])
+        if new_offset:
+            search_args['offset'] = (search_args.get('offset') or 0) + new_offset
+        result = RecordList(self._model, None, search=search_args)
+        if (is_stop_positive or key.stop is None) and key.step in (1, None):
+            return result
+        key = slice(None, limit if is_stop_positive else key.stop, key.step)
+        return super(RecordList, result).__getitem__(key)
+
     def with_env(self, env):
         if 'id' in self.__dict__:
             return super().with_env(env)

tests/test_model.py

@@ -187,7 +187,11 @@ def test_search(self):
         self.assertIsInstance(FooBar.search([searchterm]), odooly.RecordList)
         FooBar.search([searchterm], limit=2)
         FooBar.search([searchterm], offset=80, limit=99)
+        FooBar.search([searchterm], offset=80, limit=99)[100:400:3]
         FooBar.search([searchterm], order='name ASC')
+        FooBar.search([searchterm], order='name ASC')[:3]
+        FooBar.search([searchterm], order='name ASC')[40:]
+        FooBar.search([searchterm], order='name ASC')[40:99]
         FooBar.search(['name = mushroom', 'state != draft'])
         FooBar.search([('name', 'like', 'Morice')])
         FooBar.search([])
@@ -199,15 +203,14 @@ def test_search(self):
 
         FooBar.search([searchterm], limit=2).ids
         FooBar.search([searchterm], offset=80, limit=99).id
-        FooBar.search([searchterm], order='name ASC')[:3]
         FooBar.search(['name = mushroom', 'state != draft']) or 42
         FooBar.search([('name', 'like', 'Morice')]).ids
         FooBar._execute('search', [('name like Morice')])[0]
         FooBar.search([]).ids
+
         self.assertCalls(
             OBJ('foo.bar', 'search', domain, 0, 2, None),
             OBJ('foo.bar', 'search', domain, 80, 99, None),
-            OBJ('foo.bar', 'search', domain, 0, None, 'name ASC'),
             OBJ('foo.bar', 'search', domain2),
             OBJ('foo.bar', 'search', domain),
             OBJ('foo.bar', 'search', domain),
@@ -276,6 +279,25 @@ def test_search_count(self):
         self.assertCalls()
         self.assertOutput('')
 
+    def test_search_read(self):
+        FooBar = self.env['foo.bar']
+        searchterm = 'name like Morice'
+        domain = [('name', 'like', 'Morice')]
+
+        FooBar.search([searchterm], order='name ASC')[:3].name
+
+        expected_calls = [
+            OBJ('foo.bar', 'fields_get'),
+            OBJ('foo.bar', 'search_read', domain, ['name'], order='name ASC', limit=3),
+        ]
+        if float(self.server_version) < 8.0:
+            expected_calls[1:2] = [
+                OBJ('foo.bar', 'search', domain, 0, 3, 'name ASC'),
+                OBJ('foo.bar', 'read', [1001, 1002], ['name']),
+            ]
+        self.assertCalls(*expected_calls)
+        self.assertOutput('')
+
     def test_read(self):
         FooBar = self.env['foo.bar']