create and updateRecord throw exception when there is generated column

[pmtsoftware]

Let's consider blog posts as an example. In order to enable full text search on post body new column bodyIndexCol is created :

ALTER TABLE posts
    ADD COLUMN body_index_col tsvector
               GENERATED ALWAYS AS (to_tsvector('english', coalesce(body, ''))) STORED;
               
-- creating GIN index skipped due to irrelevance

After migration the Post constructor is extended with new bodyIndexCol as expected:

data Post'  = Post 
    { id :: (Id' "posts")
    , title :: Text
    , body :: Text
    , bodyIndexCol :: (Maybe TSVector) 
    , meta :: MetaBag
    } deriving (Eq, Show)

Now either creating new or updating any existing post crashes with error:

ConversionFailed 
  { errSQLType = "3 values: [\"uuid\",\"text\",\"text\"]"
  , errSQLTableOid = Nothing
  , errSQLField = ""
  , errHaskellType = "at least 4 slots in target type"
  , errMessage = "mismatch between number of columns to convert and number in target type"
  }

If we look into generated CanCreate instance for Post type:

instance CanCreate Post where
    ...
    create model = do
        List.head <$> sqlQuery "INSERT INTO posts (id, title, body) VALUES (?, ?, ?) RETURNING id, title, body" ((fieldWithDefault #id model, model.title, model.body))
    ...

we see that RETURNING clause of generated SQL insert statement contains only writeable fields (without new bodyIndexCol column) so Post constructor cannot be satisfied and leads to above error.
From db level new post was created indeed. Similar problem with createMany and update.