chore(deps-dev): bump ruff from 0.15.21 to 0.16.0 in the python-minor-patch group across 1 directory

.github/workflows/lint.yml

@@ -39,7 +39,7 @@ jobs:
         with:
           python-version: '3.14'
       - name: Install pinned linters (keep in sync with pyproject [dev])
-        run: pip install ruff==0.15.21 black==26.5.1
+        run: pip install ruff==0.16.0 black==26.5.1
       - name: Ruff
         run: ruff check diff_diff tests
       - name: Black

CHANGELOG.md

@@ -56,6 +56,17 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   three modes now dispatch, and `"error"` raises naming the skipped pairs.
 
 ### Changed
+- **Internal: `ruff` dev-tooling pin bumped `0.15.21` -> `0.16.0`** (Dependabot +
+  manual `lint.yml` sync). 0.16.0 expands ruff's *default* rule selection from
+  59 rules across 2 linter families to **413 across 38** (`B`, `PL*`, `PYI`,
+  `RUF`, `SIM`, `UP`, ...). This repo is insulated because
+  `[tool.ruff.lint] select = ["E", "F", "I", "W"]` is explicit: the resolved set
+  is the same **68 rules** under both pins (17 `E`, 43 `F`, 2 `I`, 6 `W`, per
+  `ruff check --show-settings`), and 0.16.0's three preview-to-stable promotions
+  (`FURB164`, `FURB192`, `ISC004`) fall outside those families.
+  `ruff check diff_diff tests` and `black --check` are clean on both pins.
+  **That explicit `select` is load-bearing** - dropping it to inherit ruff's
+  defaults would now enable ~7x more rules.
 - **`WooldridgeDiD` now raises when rank reduction removes any requested
   cohort×time cell**, instead of reporting the survivors under their original
   `ATT(g,t)` labels. Once a cell is dropped, the remaining coefficients

CONTRIBUTING.md

@@ -19,6 +19,12 @@ mypy diff_diff
   Refresh with `pip install -e ".[dev]"`. The pinned tools require
   Python >= 3.10 (dev tooling only; the library itself still supports
   Python 3.9).
+- `[tool.ruff.lint] select = ["E", "F", "I", "W"]` is deliberately explicit and
+  is **load-bearing**, not a restatement of ruff's defaults. Ruff 0.16.0 expanded
+  its default selection from 59 rules to 413 across 38 linter families; the
+  explicit `select` is what keeps a ruff upgrade from silently enabling hundreds
+  of new rules. Do not drop it to inherit the defaults. Widening the rule set is
+  a deliberate PR of its own.
 - `[tool.ruff.lint.per-file-ignores]` entries are deliberate (trop
   logger-before-imports E402, honest_did math-notation `l` E741, `__init__`
   re-export F401, conftest import ordering E402). Do not "fix" those patterns

pyproject.toml

@@ -65,7 +65,7 @@ dev = [
     # NOTE: black/mypy require Python >= 3.10 (dev tooling only; the library
     # floor stays 3.9).
     "black==26.5.1",
-    "ruff==0.15.21",
+    "ruff==0.16.0",
     "mypy==2.3.0",
     "maturin>=1.4,<2.0",
     "matplotlib>=3.5",