Clean Up Old noqa Comments

Your project has collected # noqa comments over two years. A # noqa comment at the end of a line tells Ruff to hide findings on that line. # noqa: T201 hides only rule T201. A bare # noqa, with no codes, hides findings of every rule. When someone fixes the code and leaves the comment behind, it hides nothing today. It will hide the next finding of that rule on that line.

To see what each comment hides, run Ruff with --ignore-noqa, which ignores the comments. --quiet drops the summary at the end, so every line of output is a finding:

ruff check --ignore-noqa --output-format concise --quiet app.py

Each output line gives the file, the line, the column, the rule code and a message:

app.py:3:1: T201 `print` found

Write code that works out which codes each comment still needs:

source = "import os  # noqa: F401\n\nprint(os.getcwd())  # noqa: T201, E722\n"
needed_codes(source, ["app.py:3:1: T201 `print` found"])
# {1: [], 3: ["T201"]}

The code uses os, so the comment on line 1 hides nothing. On line 3, Ruff found only T201, so E722 can go.

What to write

Fill in parse_finding and needed_codes.

• parse_finding(output_line) returns a Finding with the line number and the rule code. An output line looks like path:line:column: CODE message. Paths contain no colons.
• needed_codes(source, output) returns a dict with one entry for each line of source that contains # noqa. Lines count from 1.
• A colon and one or more codes can follow # noqa. Commas, spaces or both separate the codes. The first code can come right after the colon.
• Text after a second # is a note. Ignore it.
• For a comment that lists codes, keep each code that a finding on the same line has. Keep them in the comment's order.
• For a bare # noqa, list the codes of the findings on its line, sorted, each once. Listing the codes lets Ruff still report every other rule on that line.

Edge cases

• An empty list means the comment hides nothing.
• One line can have the same code twice, such as two print calls. List it once.
• output can be empty, and so can source.

What the driver reports

Keep solve as it is. It returns comments, one string per # noqa comment, in line order. "line 3: # noqa: T201" shows how the comment should read, and "line 1: delete" means it hides nothing.

Going further

Ruff can run this check for you. Rule RUF100 reports codes that hide nothing. Select it, and ruff check --fix removes them. Rule PGH004 reports every bare # noqa.