feat(order): add support for order by NULLS LAST and NULLS FIRST

related: #301

cubicweb/server/sources/rql2sql.py

@@ -895,7 +895,7 @@ class SQLGenerator(object):
                 for sortterm in sorts:
                     _term = self._sortterm_sql(sortterm, selectidx)
                     if _term is not None:
-                        sqlsortterms.append(_term)
+                        sqlsortterms.append((_term, sortterm.asc, sortterm.nulls_sort))
                 if sqlsortterms:
                     sql = self.dbhelper.sql_add_order_by(
                         sql, sqlsortterms, origselection, fneedwrap,
@@ -982,10 +982,7 @@ class SQLGenerator(object):
             sqlterm = term.accept(self)
             if sqlterm is None:
                 return None
-        if sortterm.asc:
-            return str(sqlterm)
-        else:
-            return '%s DESC' % sqlterm
+        return str(sqlterm)
 
     def visit_and(self, et):
         """generate SQL for a AND subtree"""

cubicweb/server/test/unittest_rql2sql.py

@@ -1440,6 +1440,26 @@ FROM cw_CWUser AS _X
 WHERE _X.cw_login ~ [0-9].*
 ''')
 
+    def test_order_by_nulls_first_and_last(self):
+        for rql, sql in [
+            (
+                    'Any N ORDERBY 1 NULLSFIRST WHERE X name N, X is State',
+                    '''
+SELECT _X.cw_name
+FROM cw_State AS _X
+ORDER BY 1 NULLS FIRST'''
+            ),
+            (
+                    'Any N ORDERBY 1 NULLSLAST WHERE X name N, X is State',
+                    '''
+SELECT _X.cw_name
+FROM cw_State AS _X
+ORDER BY 1 NULLS LAST'''
+            ),
+        ]:
+            with self.subTest(rql=rql):
+                self._check(rql, sql)
+
     def test_aggregate_in_orderby(self):
         self._check("Any X GROUPBY X ORDERBY ABS(COUNT(Y)) WHERE"
                     "X is CWGROUP, Y is CWUSER, Y in_group X",
@@ -1862,6 +1882,26 @@ FROM cw_CWUser AS _X
 WHERE _X.cw_login REGEXP [0-9].*
 ''')
 
+    def test_order_by_nulls_first_and_last(self):
+        for rql, sql in [
+            (
+                    'Any N ORDERBY 1 NULLSFIRST WHERE X name N, X is State',
+                    '''
+SELECT _X.cw_name
+FROM cw_State AS _X
+ORDER BY 1 is NULL DESC, 1'''
+            ),
+            (
+                    'Any N ORDERBY 1 NULLSLAST WHERE X name N, X is State',
+                    '''
+SELECT _X.cw_name
+FROM cw_State AS _X
+ORDER BY 1 is NULL, 1'''
+            ),
+        ]:
+            with self.subTest(rql=rql):
+                self._check(rql, sql)
+
     def test_union(self):
         for rql, sql in [
             ('(Any N ORDERBY 1 WHERE X name N, X is State)'

doc/book/annexes/rql/language.rst

@@ -13,8 +13,8 @@ Reserved keywords
 ::
 
   AND, ASC, BEING, DELETE, DESC, DISTINCT, EXISTS, FALSE, GROUPBY,
-  HAVING, ILIKE, INSERT, LIKE, LIMIT, NOT, NOW, NULL, OFFSET,
-  OR, ORDERBY, SET, TODAY, TRUE, UNION, WHERE, WITH
+  HAVING, ILIKE, INSERT, LIKE, LIMIT, NOT, NOW, NULL, NULLSFIRST, NULLSLAST,
+  OFFSET, OR, ORDERBY, SET, TODAY, TRUE, UNION, WHERE, WITH
 
 The keywords are not case sensitive. You should not use them when defining your
 schema, or as RQL variable names.
@@ -288,6 +288,18 @@ order: variable or column number followed by sorting method (``ASC``,
 ``DESC``), ``ASC`` being the default. If the sorting method is not
 specified, then the sorting is ascendant (`ASC`).
 
+It is also possible to precise a specific ordering for `NULL` values.
+The NULLSFIRST and NULLSLAST options can be used to determine whether
+nulls appear before or after non-null values in the sort ordering.
+By default, null values sort as if larger than any non-null value;
+that is, NULLSFIRST is the default for DESC order, and NULLSLAST otherwise.
+These options are written after the sorting method when it is specified.
+For instance, this request will return all projects ordered by creation date
+in descending order, with projects with no date in last position.
+
+.. sourcecode:: sql
+
+    Any X ORDERBY Y DESC NULLSLAST WHERE X creation_date Y
 
 Pagination
 ``````````

requirements/from-forge.txt

@@ -4,4 +4,4 @@ hg+https://forge.extranet.logilab.fr/open-source/logilab-constraint/
 hg+https://forge.extranet.logilab.fr/open-source/logilab-mtconverter/
 hg+https://forge.extranet.logilab.fr/open-source/yams/
 hg+https://forge.extranet.logilab.fr/CubicWeb/RQL/
-https://github.com/logilab/yapps/tarball/master#egg=yapps
+https://github.com/logilab/yapps/tarball/master#egg=yapps2

setup.py

@@ -65,10 +65,10 @@ setup(
     install_requires=[
         'logilab-common >= 1.8.0',
         'logilab-mtconverter >= 0.9.2',
-        'rql >= 0.36.1',
+        'rql >= 0.37.0, < 1.0.0',
         'yams >= 0.45.3',
         'lxml',
-        'logilab-database >= 1.17.2',
+        'logilab-database >= 1.18.0, < 2.0.0',
         'passlib >= 1.7',
         'pytz',
         'Markdown',