ADD: Optional choice to add a limit to requests

lizmap_server/expression_service.py

@@ -782,6 +782,7 @@ def virtualFields(params: Dict[str, str], response: QgsServerResponse, project:
             FILTER=An expression to filter layer
             FIELDS=list of requested field separated by comma
             WITH_GEOMETRY=False
+            LIMIT=number of features to return or nothing to return all
         """
         logger = Logger()
         layer_name = params.get('LAYER', '')
@@ -865,6 +866,16 @@ def virtualFields(params: Dict[str, str], response: QgsServerResponse, project:
 
         req = QgsFeatureRequest()
 
+        # set limit
+        req_limit = params.get('LIMIT', '-1')
+        try:
+            req.setLimit(int(req_limit))
+        except ValueError:
+            raise ExpressionServiceError(
+                "Bad request error",
+                f"Invalid LIMIT for 'VirtualFields': \"{req_limit}\"",
+                400)
+
         # get filter
         req_filter = params.get('FILTER', '')
         if req_filter:

test/test_expression_service_virtualfields.py

@@ -204,3 +204,39 @@ def test_request_with_filter_fields_geometry(client):
     assert b['features'][0]['properties']['a'] == 1
     assert 'b' in b['features'][0]['properties']
     assert b['features'][0]['properties']['b'] == 2
+
+def test_request_limit(client):
+    """  Test Expression VirtualFields request
+    """
+    projectfile = "france_parts.qgs"
+
+    # Make a request
+    qs = "?SERVICE=EXPRESSION&REQUEST=VirtualFields&MAP=france_parts.qgs&LAYER=france_parts"
+    qs += "&VIRTUALS={\"a\":\"%s\", \"b\":\"%s\"}" % (
+        quote('1', safe=''), quote('1 + 1', safe=''))
+    qs += "&LIMIT=2"
+    rv = client.get(qs, projectfile)
+    assert rv.status_code == 200
+    assert rv.headers.get('Content-Type', '').find('application/json') == 0
+
+    b = json.loads(rv.content.decode('utf-8'))
+    assert 'type' in b
+    assert b['type'] == 'FeatureCollection'
+
+    assert 'features' in b
+    assert len(b['features']) == 2
+
+    assert 'type' in b['features'][0]
+    assert b['features'][0]['type'] == 'Feature'
+
+    assert 'geometry' in b['features'][0]
+    assert b['features'][0]['geometry'] is None
+
+    assert 'properties' in b['features'][0]
+    assert 'NAME_1' in b['features'][0]['properties']
+    assert 'Region' in b['features'][0]['properties']
+
+    assert 'a' in b['features'][0]['properties']
+    assert b['features'][0]['properties']['a'] == 1
+    assert 'b' in b['features'][0]['properties']
+    assert b['features'][0]['properties']['b'] == 2