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d7144d6d8e
## Summary
The ruff configuration section is called "format", rather than
"preview". Using the configuration as it was written in the docs gives
an error:
```
$ ruff format --check .
ruff failed
Cause: TOML parse error at line 143, column 1
|
143 | [tool.ruff.preview]
| ^^^^^^^^^^^^^^^^^^^
invalid type: map, expected a boolean
```
## Test Plan
Tested running `ruff format` with the following in my `pyproject.toml`:
```toml
[tool.ruff.format]
preview = true
```
and it worked properly (using preview rules for formatting).
154 lines
3.6 KiB
Markdown
154 lines
3.6 KiB
Markdown
# Preview
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Ruff includes an opt-in preview mode to provide an opportunity for community feedback and increase confidence that
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changes are a net-benefit before enabling them for everyone.
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Preview mode enables a collection of newer lint rules, fixes, and formatter style changes that are
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considered experimental or unstable,.
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## Enabling preview mode
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Preview mode can be enabled with the `--preview` flag on the CLI or by setting `preview = true` in your Ruff
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configuration file.
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Preview mode can be configured separately for linting and formatting (requires Ruff v0.1.1+). To enable preview lint rules without preview style formatting:
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=== "pyproject.toml"
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```toml
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[tool.ruff.lint]
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preview = true
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```
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=== "ruff.toml"
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```toml
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[lint]
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preview = true
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```
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To enable preview style formatting without enabling any preview lint rules:
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=== "pyproject.toml"
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```toml
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[tool.ruff.format]
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preview = true
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```
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=== "ruff.toml"
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```toml
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[format]
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preview = true
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```
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## Using rules that are in preview
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If a rule is marked as preview, it can only be selected if preview mode is enabled. For example, consider a
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hypothetical rule, `HYP001`. If `HYP001` were in preview, it would _not_ be enabled by adding following to your
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config file:
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=== "pyproject.toml"
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```toml
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[tool.ruff.lint]
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extend-select = ["HYP001"]
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```
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=== "ruff.toml"
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```toml
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[lint]
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extend-select = ["HYP001"]
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```
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It also would _not_ be enabled by selecting the `HYP` category, like so:
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=== "pyproject.toml"
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```toml
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[tool.ruff.lint]
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extend-select = ["HYP"]
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```
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=== "ruff.toml"
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```toml
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[lint]
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extend-select = ["HYP"]
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```
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Similarly, it would _not_ be enabled via the `ALL` selector:
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=== "pyproject.toml"
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```toml
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[tool.ruff.lint]
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select = ["ALL"]
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```
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=== "ruff.toml"
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```toml
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[lint]
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select = ["ALL"]
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```
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However, it would be enabled in any of the above cases if you enabled preview in your configuration file:
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=== "pyproject.toml"
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```toml
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[tool.ruff.lint]
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extend-select = ["HYP"]
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preview = true
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```
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=== "ruff.toml"
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```toml
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[lint]
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extend-select = ["HYP"]
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preview = true
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```
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Or, if you provided the `--preview` CLI flag.
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To see which rules are currently in preview, visit the [rules reference](rules.md).
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## Selecting single preview rules
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When preview mode is enabled, selecting rule categories or prefixes will include all preview rules that match.
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If you'd prefer to opt-in to each preview rule individually, you can toggle the `explicit-preview-rules`
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setting in your configuration file:
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=== "pyproject.toml"
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```toml
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[tool.ruff.lint]
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preview = true
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explicit-preview-rules = true
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```
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=== "ruff.toml"
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```toml
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[lint]
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preview = true
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explicit-preview-rules = true
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```
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In our previous example, `--select` with `ALL` `HYP`, `HYP0`, or `HYP00` would not enable `HYP001`. Each preview
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rule will need to be selected with its exact code, e.g. `--select ALL,HYP001`.
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If preview mode is not enabled, this setting has no effect.
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## Legacy behavior
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Before the preview mode was introduced, new rules were added in a "nursery" category that required selection of
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rules with their exact codes — similar to if `explicit-preview-rules` is enabled.
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The nursery category has been deprecated and all rules in the nursery are now considered to be in preview.
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For backwards compatibility, nursery rules are selectable with their exact codes without enabling preview mode.
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However, this behavior will display a warning and support will be removed in a future release.
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