renag

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Short for Regex (re) Nag (like “one who complains”).

Now also PEGs (Parsing Expression Grammars) compatible with pyparsing!

A Regex based linter tool that works for any language and works exclusively with custom linting rules.

Complainers

renag is based on the concept of Complainers. See renag/complainer.py for the interface to create your own Complainer and examples for some prebuilt examples.

Complainers can be as simple as the following:

class PrintComplainer(Complainer):
    """Print statements can slow down code."""

    capture = r"print\(.*\)"
    severity = Severity.WARNING
    glob = ["*.py"]

This has 4 fundamental parts:

  • docstring - The docstring of the class automatically becomes the description of the error.

  • capture - A regex statement that, if matched, will raise the complaint.

  • severity - Either WARNING which will return exit code 0, or CRITICAL which will return exit code 1.

  • glob - A list of glob wildcards that define what files to run the Complainer on.

Next you can add a check method to your Complainer if you would like something more complicated than simple regex.

class PrintComplainer(Complainer):
    """Print statements can slow down code."""
    ...

    def check(self, txt: str, path: Path, capture_span: Span) -> List[Complaint]:
          """Check that the print statement is not commented out before complaining."""
          # Get the line number
          lines, line_numbers = get_lines_and_numbers(txt, capture_span)

          # Check on the first line of the capture_span that the capture is not preceded by a '#'
          # In such a case, the print has been commented out
          if lines[0].count("#") > 0 and lines[0].index("#") < capture_span[0]:

              # If it is the case that the print was commented out, we do not need to complain
              # So we will return an empty list of complaints
              return []

          # Otherwise we will do as normal
          return super().check(txt=txt, path=path, capture_span=capture_span)

Adding to your project

Simply put this complainer in a python module in your project like so:

root/
  complainers_dir_name/
    __init__.py
    custom_complainer1.py
    custom_complainer2.py
    ...
  the-rest-of-your-project
  ...

Import each complainer inside __init__.py so it can be imported via from .{complainers_dir_name} import *.

Then add the following to your .pre-commit-hooks.yaml file:

- repo: https://github.com/ryanpeach/renag
  rev: "0.3.3"
  hooks:
    - id: renag
      args:
        - "--load_module"
        - "{complainers_dir_name}"
        - "--staged"

Run renag --help to see a list of command line arguments you can add to the hook.

Output

Complaint printout modeled after rust error reporting. Example of a Complaint:

Severity.WARNING - EasyPrintComplainer: Print statements can slow down code.
  --> renag/__main__.py
   147|                                 )
   148|                                 print()
   149|
   150|     # End by exiting the program
   151|     if N == 0:
   152|         print(color_txt("No complaints. Enjoy the rest of your day!", BColors.OKGREEN))
   152|         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   153|         exit(0)
   154|     if N_WARNINGS > 0 and N_CRITICAL == 0:
   155|         print(
   156|             color_txt(
   157|                 f"{N} Complaints found: {N_WARNINGS} Warnings, {N_CRITICAL} Critical.",

iregex

All regex captures in this module default to using iregex. iregex can help make your regex more understandable to readers, and allow you to compose large regex statements (see examples/regex.py for examples).