handle exceptions that occur inside of jinja

[drewbanin]

Issue

Issue description

Given sql with invalid jinja like:

{{ config(
    materialized = "table",
    schema = 'custom_schema' -- render this in a custom schema
) }}

dbt will throw a very unhelpful error that looks like:

  File "/usr/local/Cellar/dbt/0.10.2/libexec/lib/python3.7/site-packages/dbt/parser/base_sql.py", line 95, in parse_sql_nodes
    macros=macros)
  File "/usr/local/Cellar/dbt/0.10.2/libexec/lib/python3.7/site-packages/dbt/parser/base.py", line 105, in parse_node
    capture_macros=True)
  File "/usr/local/Cellar/dbt/0.10.2/libexec/lib/python3.7/site-packages/dbt/clients/jinja.py", line 198, in get_rendered
    return render_template(template, ctx, node)
  File "/usr/local/Cellar/dbt/0.10.2/libexec/lib/python3.7/site-packages/dbt/clients/jinja.py", line 185, in render_template
    return template.render(ctx)
  File "/usr/local/Cellar/dbt/0.10.2/libexec/lib/python3.7/site-packages/jinja2/asyncsupport.py", line 76, in render
    return original_render(self, *args, **kwargs)
  File "/usr/local/Cellar/dbt/0.10.2/libexec/lib/python3.7/site-packages/jinja2/environment.py", line 1008, in render
    return self.environment.handle_exception(exc_info, True)
  File "/usr/local/Cellar/dbt/0.10.2/libexec/lib/python3.7/site-packages/jinja2/environment.py", line 780, in handle_exception
    reraise(exc_type, exc_value, tb)
  File "/usr/local/Cellar/dbt/0.10.2/libexec/lib/python3.7/site-packages/jinja2/_compat.py", line 37, in reraise
    raise value.with_traceback(tb)
  File "<template>", line 1, in top-level template code
TypeError: exceptions must derive from BaseException

It will likely be difficult to pinpoint the exact error, but it should ideally be able to throw some sort of human-readable parsing error, indicating the model where the syntax error occurred.

[beckjake]

I can't reproduce this on any dbt versions, going back as far as 0.10.2. I consistently get this message:

Encountered an error:
Compilation Error in model bad (models/bad.sql)
  expected token ',', got 'this'
    line 3
      schema = 'custom_schema' -- render this in a custom schema

Which definitely isn't perfect, but seems pretty helpful to me. Is it possible this was fixed by a jinja update, or something like that?

I do recognize that stack trace as something I've seen in the past, and it's definitely unhelpful.

[drewbanin]

Are you #wontfix-ing me???

Agreed, I just gave this a spin and couldn't reproduce it either. I didn't see anything in the Jinja changelog that seemed germane to this issue either. Going to close this, but will keep an eye out for this behavior in the wild.

[beckjake]

Found a way to trigger this error! In a model that does not define thing: select * from {{ ref(thing + 'a') }}.
Python version 3.6 for this, I think 2.7 won't have the same issue.