Allow selecting rules with severity `warning` in preview by dylwil3 · Pull Request #23846 · astral-sh/ruff

dylwil3 · 2026-03-09T20:31:21Z

This PR allows users to specify a set of rules to enable with severity level warning (in preview).

They may do so in the CLI using --warn and --extend-warn or in a configuration file via

[lint]
warn = [ ... ]

Closes #1256

Details on Resolving the Configuration

The precedence between select and ignore, within a configuration file, is as follows:

More specific designations take precedence over less specific, e.g. --warn F --select F401 will give all Pyflakes diagnostics except F401 a severity of warning, and give F401 a severity of error.
Between designations of equal specificity, warn takes precedence over select, e.g. --select F401 --warn F401 will resolve to --warn F401.

As in the case of select vs extend-select, specifying warn = [...] will overwrite any inherited configuration for warn. However, it will not overwrite an inherited configuration for select.

For example,

ruff check --warn ARG ex.py

will return diagnostics for all default rules with error severity and then also the ARG rules with severity warning.

In order to warn on a single rule, the user has to do something like this:

ruff check --select ARG --warn ARG ex.py

which looks a bit funny.

astral-sh-bot · 2026-03-09T20:43:28Z

`ruff-ecosystem` results

Linter (stable)

✅ ecosystem check detected no linter changes.

Linter (preview)

✅ ecosystem check detected no linter changes.

This is just the "aesthetic" part of implementing `warning` severities. Configuration changes are in #23846 It's expected that the `preview` ecosystem check times out here.

dylwil3 · 2026-03-13T20:57:00Z

crates/ruff/src/lib.rs

+    {
+        warn_user_once!(
+            "Enabling rules with severity 'warning' requires preview mode, otherwise all rules are interpreted with severity 'error'."
+        );
+    }


I'd love feedback on whether or not this should be the behavior when preview is not enabled. Another option would be to interpret everything "correctly" but just warn the user that severities are in preview and experimental.

If we do like the idea of interpreting these as error there's some other design questions... for example, at the moment with preview disabled it will still "correctly" populate lint.warn if you do --show-settings. Is that we want?

dylwil3 · 2026-03-13T21:03:13Z

crates/ruff_linter/src/settings/rule_table.rs

    /// Maps rule codes to a boolean indicating if the rule should be fixed.
    enabled: RuleSet,
+    warn: RuleSet,
    should_fix: RuleSet,


I think I'm implicitly assuming that warn is a subset of enabled. I believe this invariant is ensured because the public methods that mess with these fields do the right thing (e.g. RuleTable::warn below). But let me know if there's a better way to enforce this / organize this...

This makes sense to me.

dylwil3 · 2026-03-13T21:04:03Z

crates/ruff_workspace/src/configuration.rs

+                        // Override warnings of weaker specificity
+                        // For example:
+                        // ```
+                        // select = ["F401"]
+                        // warn = ["F"]
+                        // ```
+                        // should warn on all Pyflakes rules
+                        // except for `F401` where it should error.
+                        warn_map_updates.insert(rule, false);


This prevents a bunch of the strange behavior we brought up in design discussions.

dylwil3 · 2026-03-13T21:16:54Z

I think this is ready for the first round of review. Probably most important is to see:

If we want any behavior changes compared to what you see in the CLI snapshots, and
If we want to modify how this is gated behind preview.
If there are any scenarios we want to add tests for.

Of course suggestions on improving the actual implementation are also welcome!

crates/ruff/tests/cli/lint.rs

MichaReiser

I skimmed over the CLI tests and most output does make sense. I do think that the schema overall is a bit complicated to grasp what's going on, especially if nested configurations come into play. It's also easier to accidentially list a rule twice.

I wonder if we should take a step back and discuss how we want to role out human-readable names. For example, we could use the absence of select, extend-select, ignore and extend-ignore as opt-in to human readable names so that Ruff keeps using rule-codes in its output unless a user opted in to the new configuration (because they don't have a configuration or don't select any rules or use the new configuration schema).

What would be interesting to understand is if there are cases where we think a rule-table is less intuitive than todays select/warn/ignore.

MichaReiser · 2026-03-16T08:55:27Z

crates/ruff/tests/cli/lint.rs

+    success: false
+    exit_code: 1
+    ----- stdout -----
+    try.py:1:8: error[F401] [*] `os` imported but unused


We should also test that some other F rule now has warning severity

MichaReiser · 2026-03-16T08:59:25Z

crates/ruff/tests/cli/lint.rs

+    ----- stderr -----
+    "###
+    );
+    Ok(())


Can you add some more tests demonstrating:

extend-* combinations. Especially combinations of extend- and non-extend configurations

How select behaves when there are rules that default to warning severity.

MichaReiser · 2026-03-16T09:00:45Z

crates/ruff_linter/src/settings/rule_table.rs

    /// Maps rule codes to a boolean indicating if the rule should be fixed.
    enabled: RuleSet,
+    warn: RuleSet,
    should_fix: RuleSet,


This makes sense to me.

MichaReiser · 2026-03-16T09:06:44Z

crates/ruff/tests/cli/lint.rs

+        r#"
+[lint]
+preview = true
+select = ["F401"]


Can you add a test that demonstrates the opposite: The outer configuration warning about F401 and the nested configuration selecting F401

MichaReiser · 2026-03-26T07:42:48Z

I hope it's okay if I put this back to draft or is there something you want feedback on?

dylwil3 added configuration Related to settings and configuration cli Related to the command-line interface preview Related to preview mode features labels Mar 9, 2026

dylwil3 mentioned this pull request Mar 10, 2026

Display output severity in preview #23845

Merged

dylwil3 force-pushed the dylan/warnings branch 2 times, most recently from 7e2e587 to 7c9514a Compare March 13, 2026 14:17

dylwil3 force-pushed the dylan/output-severity branch from 33fdbb8 to cb221a4 Compare March 13, 2026 14:18

dylwil3 force-pushed the dylan/warnings branch 2 times, most recently from fd38c83 to 42d047a Compare March 13, 2026 14:27

dylwil3 force-pushed the dylan/output-severity branch from cb221a4 to e11289c Compare March 13, 2026 14:43

dylwil3 force-pushed the dylan/warnings branch from 42d047a to 3d9da14 Compare March 13, 2026 14:46

Base automatically changed from dylan/output-severity to main March 13, 2026 14:56

dylwil3 force-pushed the dylan/warnings branch 8 times, most recently from 16f5460 to cd03169 Compare March 13, 2026 21:14

dylwil3 commented Mar 13, 2026

View reviewed changes

dylwil3 changed the title ~~[WIP] Allow selecting rules with severity warning in preview~~ Allow selecting rules with severity warning in preview Mar 13, 2026

dylwil3 requested review from MichaReiser, amyreese and ntBre March 13, 2026 21:17

dylwil3 marked this pull request as ready for review March 13, 2026 21:19

astral-sh-bot bot assigned amyreese Mar 13, 2026

dylwil3 commented Mar 13, 2026

View reviewed changes

crates/ruff/tests/cli/lint.rs Outdated Show resolved Hide resolved

MichaReiser reviewed Mar 16, 2026

View reviewed changes

dylwil3 added 10 commits March 25, 2026 15:37

add warn and extend-warn to options

e56d435

add warn and extend-warn to configuration

3080790

add warn to rule table

91844f8

specify severity in diagnostics

5f728d7

hook into CLI

5ecc138

properly gate with preview

95e16c1

update schema and docs

0fc9bb1

snapshots

49e2aff

use "diagnostic" instead of "error" in summary text

372bf5f

snapshots for new summary noun

3701786

dylwil3 force-pushed the dylan/warnings branch from 879195a to 3701786 Compare March 25, 2026 20:37

MichaReiser marked this pull request as draft March 26, 2026 07:42

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Allow selecting rules with severity `warning` in preview#23846

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