Python templater

Uses native Python f-strings. As described in Generic Templating, an example usage would look be configured as follows:

If passed the following .sql file:

SELECT * FROM {tbl_name}

...and the following configuration in .sqlfluff in the same directory:

[sqlfluff]
templater = python

[sqlfluff:templater:python:context]
tbl_name = my_table

...then before parsing, the sql will be transformed to:

SELECT * FROM my_table

Complex Python Variable Templating

Python string formatting supports accessing object attributes via dot notation (e.g. {foo.bar}). However, since we cannot create Python objects within configuration files, we need a workaround in order to provide dummy values to render templates containing these values. The SQLFluff python templater will interpret any variable containing a "." as a dictionary lookup on the magic fixed context key sqlfluff.

-- this SQL
SELECT * FROM {foo.bar}

-- becomes this
SELECT * FROM {sqlfluff["foo.bar"]}

..which can be populated using the following configuration:

[sqlfluff:templater:python:context]
sqlfluff = {"foo.bar": "abc"}