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Ruff uses a custom versioning scheme that uses the minor version number for breaking changes and the patch version number for bug fixes. Ruff does not yet have a stable API; once Ruff's API is stable, the major version number and semantic versioning will be used.

Version changes#

Minor version increases will occur when:

  • A deprecated option or feature is removed
  • Configuration changes in a backwards incompatible way
    • This may occur in minor version changes until 1.0.0, however, it should generally be avoided.
  • Support for a new file type is promoted to stable
  • Support for an end-of-life Python version is dropped
  • Linter:
    • A rule is promoted to stable
    • The behavior of a stable rule is changed
      • The scope of a stable rule is significantly increased
      • The intent of the rule changes
      • Does not include bug fixes that follow the original intent of the rule
    • Stable rules are added to the default set
    • Stable rules are removed from the default set
    • A safe fix for a rule is promoted to stable
  • Formatter:
    • The stable style changed

Patch version increases will occur when:

  • Bugs are fixed, including behavior changes that fix bugs
  • A new configuration option is added in a backwards compatible way (no formatting changes or new lint errors)
  • Support for a new Python version is added
  • Support for a new file type is added in preview
  • An option or feature is deprecated
  • Linter:
    • An unsafe fix for a rule is added
    • A safe fix for a rule is added in preview
    • The scope of a rule is increased in preview
    • A fix’s applicability is demoted
    • A rule is added in preview
    • The behavior of a preview rule is changed
  • Formatter:
    • The stable style changed to prevent invalid syntax, changes to the program's semantics, or removal of comments
    • The preview style changed

Preview mode#

A preview mode is available to enable new, unstable rules and features, e.g., support for a new file type.

The preview mode is intended to help us collect community feedback and gain confidence that changes are a net-benefit.

The preview mode is not intended to gate access to work that is incomplete or features that we are likely to remove. However, we reserve the right to make changes to any behavior gated by the mode including the removal of preview features or rules.

Rule stabilization#

When modifying or adding rules, we use the following guidelines:

  • New rules should always be added in preview mode
  • New rules will remain in preview mode for at least one minor release before being promoted to stable
    • If added in a patch release i.e. 0.6.1 then a rule will not be eligible for stability until 0.8.0
  • Stable rule behaviors are not changed significantly in patch versions
  • Promotion of rules to stable may be delayed in order to “batch” them into a single minor release
  • Not all rules in preview need to be promoted in a given minor release

Fix stabilization#

Fixes have three applicability levels:

  • Display: Never applied, just displayed.
  • Unsafe: Can be applied with explicit opt-in.
  • Safe: Can be applied automatically.

Fixes for rules may be introduced at a lower applicability, then promoted to a higher applicability. Reducing the applicability of a fix is not a breaking change. The applicability of a given fix may change when the preview mode is enabled.