tseruga opened a new issue, #28218:
URL: https://github.com/apache/superset/issues/28218

   ### Bug description
   
   Unsure of when this regression happened, but it likely happened part of 
#26476 or #27470 
   
   Within the `BaseTemplateProcessor` base class, we have the following method 
interface for `process_template()`:
   
   
https://github.com/apache/superset/blob/52f8734662cdeadba1a4ae80be3e2c74ad8f85a9/superset/jinja_context.py#L493-L504
   
   Specifically, the type of `sql` should be a `str`.
   
   It appears that this contract is being broken after one or more of the above 
changes. Instead, this method (when implemented and assigned to an engine) will 
sometimes be passed a `jinja2.nodes.Template` type object.
   
   One example of this is here:
   
https://github.com/apache/superset/blob/52f8734662cdeadba1a4ae80be3e2c74ad8f85a9/superset/sql_parse.py#L1524-L1579
   
   We see that we grab the template processor, then convert the raw `str` to a 
`Template` object:
   ```
       processor = get_template_processor(database)
       template = processor.env.parse(sql)
   ```
   
   This `Template` object is then passed to the `process_template()` method:
   
   ```
   
       return (
           tables
           | ParsedQuery(
               sql_statement=processor.process_template(template),
               engine=database.db_engine_spec.engine,
           ).tables
       )
   ```
   
   Which breaks the contract set by the `BaseTemplateProcessor` interface.
   
   The example implementation of a custom template processor also makes the 
assumption that the argument will always be a string as shown here:
   
   
https://github.com/apache/superset/blob/master/docs/docs/configuration/sql-templating.mdx?plain=1#L123-L149
   
   I believe this example implementation will also break upon receiving a 
`Template` object instead of a string.
   
   ### How to reproduce the bug
   
   1. Enable `ENABLE_TEMPLATE_PROCESSING` in `config.py`
   2. Implement a custom template processor extending the 
`BaseTemplateProcessor`
   3. Within `process_template()` perform a string operation
   Ex:
   ```
   class ExampleTemplateProcessor(BaseTemplateProcessor):
       def process_template(self, sql: str, **kwargs: Any) -> str:
           return sql.upper()
   ```
   4. Wire up the new template processor an engine that you can query (I used 
`sqllite` since that's what the example data uses)
   ```
   DEFAULT_PROCESSORS = {
       "presto": PrestoTemplateProcessor,
       "hive": HiveTemplateProcessor,
       "trino": TrinoTemplateProcessor,
       "sqlite": ExampleTemplateProcessor,
   }
   ```
   I added this to the list of `DEFAULT_PROCESSORS` for testing, but this also 
happens when using `CUSTOM_TEMPLATE_PROCESSORS` via the config.
   5. Attempt to query in sql labs - this should work as expected:
   6. Go to Sql Labs -> Query History
   7. Observe that the template processor now fails since it is passed a 
`Template` object
   
   ```
   2024-04-25 11:22:34,467:ERROR:superset.views.base:'Template' object has no 
attribute 'upper'
   Traceback (most recent call last):
   ...
     File "...superset/sql_parse.py", line 1576, in 
extract_tables_from_jinja_sql
       sql_statement=processor.process_template(template),
     File "...superset/jinja_context.py", line 665, in process_template
       return sql.upper()
   AttributeError: 'Template' object has no attribute 'upper'
   ```
   
   
   ### Screenshots/recordings
   
   _No response_
   
   ### Superset version
   
   master / latest-dev
   
   ### Python version
   
   3.10
   
   ### Node version
   
   16
   
   ### Browser
   
   Firefox
   
   ### Additional context
   
   Feature flag: `ENABLE_TEMPLATE_PROCESSING`
   
   ### Checklist
   
   - [X] I have searched Superset docs and Slack and didn't find a solution to 
my problem.
   - [X] I have searched the GitHub issue tracker and didn't find a similar bug 
report.
   - [X] I have checked Superset's logs for errors and if I found a relevant 
Python stacktrace, I included it here as text in the "additional context" 
section.


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