Add pre-commit.

Author: lohedges

.pre-commit-config.yaml

@@ -0,0 +1,23 @@
+files: ^(src|tests)/
+exclude: ^tests/(input|output)/
+
+repos:
+  # General file quality checks
+  - repo: https://github.com/pre-commit/pre-commit-hooks
+    rev: v5.0.0
+    hooks:
+      - id: trailing-whitespace
+      - id: end-of-file-fixer
+      - id: check-added-large-files
+        args: [--maxkb=1000]  # Prevent files larger than 1MB
+      - id: check-merge-conflict
+
+  # Python formatting and linting
+  - repo: https://github.com/astral-sh/ruff-pre-commit
+    rev: v0.8.4
+    hooks:
+      # Run the formatter
+      - id: ruff-format
+      # Run the linter (optional - remove if too strict)
+      - id: ruff
+        args: [--fix, --exit-zero]  # Auto-fix but don't block commits

README.md

@@ -72,6 +72,24 @@ Then install `loch` into the environment:
 pip install -e .
 ```
 
+## Development
+
+Pre-commit hooks are used to ensure consistent code formatting and linting.
+To set up pre-commit in your development environment:
+
+```
+pixi shell -e dev
+pre-commit install
+```
+
+This will run [ruff](https://docs.astral.sh/ruff/) formatting and linting
+checks automatically on each commit. To run the checks manually against all
+files:
+
+```
+pre-commit run --all-files
+```
+
 ## How does it work?
 
 Instead of computing the energy change for each trial insertion/deletion with

pyproject.toml

@@ -29,3 +29,9 @@ distance-dirty = "{base_version}+{distance}.{vcs}{rev}.dirty"
 
 [tool.versioningit.write]
 file = "src/loch/_version.py"
+
+[tool.ruff.lint]
+ignore = ["E402"]
+
+[tool.ruff.lint.per-file-ignores]
+"tests/**" = ["F841"]

src/loch/_sampler.py

@@ -2394,7 +2394,6 @@ def _set_water_state(self, context, indices=None, states=None, force=False):
 
         # Loop over the indices and states.
         for idx, state in zip(indices, states):
-
             # Skip if the state is unchanged.
             if not force and self._water_state[idx] == state:
                 continue