Adding Custom Rules to the SQL Lint Tool SQLFluff
databaseThe SQL lint tool sqlfluff has a mechanism to add custom rules via plugins.
Create a plugin by referring to the example plugin.
Implement _eval() that evaluates rules and returns a LintResult in a Rule_XXXX class that inherits from BaseRule.
# my_custom_rules/rules.py
from sqlfluff.core.rules import (
BaseRule,
LintResult,
RuleContext,
)
from sqlfluff.core.rules.crawlers import SegmentSeekerCrawler
class Rule_Example_L001(BaseRule):
'''
test rule
'''
groups = ("all",)
config_keywords = ["aaa"]
crawl_behaviour = SegmentSeekerCrawler({"select_clause"})
is_fix_compatible = True
def __init__(self, *args, **kwargs):
super().__init__(*args, **kwargs)
print("---- init ----")
print(f"parameter: aaa={self.aaa}")
def _eval(self, context: RuleContext):
print("---- eval ----")
for seg in context.segment.segments:
print(seg.get_type(), seg.raw.lower())
if seg.get_type() == 'select_clause_element' and seg.raw.lower() == 'b':
return LintResult(
anchor=seg,
description=f"Don't select b!",
)
Return this class in get_rules() in __init__.py.
# my_custom_rules/__init__.py
from typing import Any, Dict, List, Type
from sqlfluff.core.config import load_config_resource
from sqlfluff.core.plugin import hookimpl
from sqlfluff.core.rules import BaseRule
@hookimpl
def get_rules() -> List[Type[BaseRule]]:
from my_custom_rules.rules import Rule_Example_L001
return [Rule_Example_L001]
@hookimpl
def load_default_config() -> Dict[str, Any]:
"""Loads the default configuration for the plugin."""
return load_config_resource(
package="my_custom_rules",
file_name="plugin_default_config.cfg",
)
@hookimpl
def get_configs_info() -> Dict[str, Dict[str, Any]]:
"""Get rule config validations and descriptions."""
return {
"aaa": {"definition": "aaaa"},
}
After placing pyproject.toml and running pip install, SQLFluff will recognize and apply the lint.
$ cat pyproject.toml
[build-system]
requires = ["setuptools>=40.8.0", "wheel"]
build-backend = "setuptools.build_meta"
[project]
name = "sqlfluff-my-custom-rules"
version = "1.0.0"
requires-python = ">=3.8"
dependencies = [
"sqlfluff>=2.2.2"
]
[project.entry-points.sqlfluff]
my_custom_rules = "my_custom_rules"
$ pip install -e .
$ cat test.sql
SELECT
a,
b
FROM table
ORDER BY bar;
$ sqlfluff lint --dialect ansi test.sql
---- init ----
parameter: aaa=bbb
rule Example_L001: 0%| | 0/68 [00:00<?, ?it/s]
---- eval ----
keyword select
indent
newline
whitespace
select_clause_element a
comma ,
newline
whitespace
select_clause_element b
== [test.sql] FAIL
L: 3 | P: 5 | Example_L001 | Don't select b!
All Finished 📜 🎉!