JSON has_key causes 'TypeError: can only concatenate tuple (not "list") to tuple' in Django 2.2.6

[Shaheed Haque]

In Django 2.2.6, but not in Django 2.2.5, this query causes the exception shown:

>>> models.PayRun.objects.filter(snapshot__employee__has_key='6')
Traceback (most recent call last):
  File "/usr/lib/python3.6/code.py", line 91, in runcode
    exec(code, self.locals)
  File "<console>", line 1, in <module>
  File "/usr/local/lib/python3.6/dist-packages/django/db/models/query.py", line 250, in __repr__
    data = list(self[:REPR_OUTPUT_SIZE + 1])
  File "/usr/local/lib/python3.6/dist-packages/django/db/models/query.py", line 274, in __iter__
    self._fetch_all()
  File "/usr/local/lib/python3.6/dist-packages/django/db/models/query.py", line 1242, in _fetch_all
    self._result_cache = list(self._iterable_class(self))
  File "/usr/local/lib/python3.6/dist-packages/viewflow/managers.py", line 87, in __iter__
    for process in base_iterator:
  File "/usr/local/lib/python3.6/dist-packages/django/db/models/query.py", line 55, in __iter__
    results = compiler.execute_sql(chunked_fetch=self.chunked_fetch, chunk_size=self.chunk_size)
  File "/usr/local/lib/python3.6/dist-packages/django/db/models/sql/compiler.py", line 1087, in execute_sql
    sql, params = self.as_sql()
  File "/usr/local/lib/python3.6/dist-packages/django/db/models/sql/compiler.py", line 489, in as_sql
    where, w_params = self.compile(self.where) if self.where is not None else ("", [])
  File "/usr/local/lib/python3.6/dist-packages/django/db/models/sql/compiler.py", line 405, in compile
    sql, params = node.as_sql(self, self.connection)
  File "/usr/local/lib/python3.6/dist-packages/django/db/models/sql/where.py", line 81, in as_sql
    sql, params = compiler.compile(child)
  File "/usr/local/lib/python3.6/dist-packages/django/db/models/sql/compiler.py", line 405, in compile
    sql, params = node.as_sql(self, self.connection)
  File "/usr/local/lib/python3.6/dist-packages/django/contrib/postgres/lookups.py", line 11, in as_sql
    params = lhs_params + rhs_params
TypeError: can only concatenate tuple (not "list") to tuple

The model field in question looks like this:

    snapshot = JSONField(encoder=DjangoJSONEncoder, default=dict, blank=True)

The code and variables ​at the point of failure look like this:

(Pdb) list
  6  
  7     class PostgresSimpleLookup(Lookup):
  8         def as_sql(self, qn, connection):
  9             lhs, lhs_params = self.process_lhs(qn, connection)
 10             rhs, rhs_params = self.process_rhs(qn, connection)
 11 B->         params = lhs_params + rhs_params
 12             return '%s %s %s' % (lhs, self.operator, rhs), params
 13  
 14  
 15     class DataContains(PostgresSimpleLookup):
 16         lookup_name = 'contains'
(Pdb) lhs
'("paiyroll_payrun"."snapshot" -> %s)'
(Pdb) lhs_params
('employee',)
(Pdb) rhs
'%s'
(Pdb) rhs_params
['6']

Thus, process_lhs() and process_rhs() are producing results which cannot be combined.

[Mariusz Felisiak]

Thanks for this report, we're going to fix this in Django 2.2.7.

Duplicate of #30826.

[Claude Paroz]

Maybe we should release 2.2.7 ASAP?

[Carlton Gibson]

Hmmm. Personally, I don't think it's an emergency. v2.2.7 (&co) will already be the third pass at catching the regression(s) introduced by the security patch for v2.2.4. I'd rather hold the schedule to give us the best chance at making sure we won't need a forth. But happy if you want to raise it on the list for discussion Claude. :)

[Claude Paroz]

I'm fully trusting your judgment!