misc: don't break on incomplete ezt "for" expression (#20721)

tests/api/test_all.py

@@ -100,6 +100,12 @@ def test_validate_expression(pub):
     resp = get_app(pub).get('/api/validate-expression?expression={{hello+%C3%A9l%C3%A9phant}}')
     assert resp.json['klass'] == 'error'
     assert resp.json['msg'].startswith('syntax error in Django template: Could not parse the remainder')
+    # broken ezt
+    resp = get_app(pub).get('/api/validate-expression?expression=[for]')
+    assert resp.json == {
+        'klass': 'error',
+        'msg': 'syntax error in ezt template: wrong number of arguments at line 1 and column 1',
+    }
 
 
 def test_validate_condition(pub):

wcs/qommon/ezt.py

@@ -413,6 +413,8 @@ class Template:
                         raise ArgCountSyntaxError(str(args[1:]), line, column)
                     # this assumes arg1 is always a ref unless cmd is 'define'
                     if cmd != 'define':
+                        if len(args) < 2:
+                            raise ArgCountSyntaxError(str(args), line, column)
                         args[1] = _prepare_ref(args[1], for_names, file_args)
 
                     # handle arg2 for the 'is' command