Breaking

• The command line syntax has slightly changed due to migrating from the Commandant command line parsing library to swift-argument-parser. For the most part the breaking changes are all to make the syntax more unix compliant and intuitive to use. For example, commands such as swiftlint --help or swiftlint -h now work as expected. The help output from various commands has greatly improved as well. Notably: swiftlint autocorrect was removed in favor of swiftlint --fix. Previous commands should continue to work temporarily to help with the transition. Please let us know if there's a command that no longer works and we'll attempt to add a bridge to help with its transition.
  JP Simard

• Configuration files now consistently have their included/excluded relative file paths applied relative to their location in the file system. Previously the root configuration file applied these relative to the current working directory, but nested configurations applied these to their location in the file system.
  Frederick Pietschmann JP Simard

• The discarded_notification_center_observer is now opt-in due to some difficult to resolve false positives, such as #3498.
  JP Simard

Experimental

• None.

Enhancements

• Added allows_single_line option in multiline_parameters rule configuration. Defaults to true. This enforces parameters in a method with multiple parameters to always be in different lines.
  Otavio Cordeiro

• Support relative paths in compilation databases for SwiftLint analyzer rules.
  JP Simard

• Add opt-in rule discouraged_assert to encourage the use of assertionFailure() and/or preconditionFailure() over assert(false).
  Otavio Cordeiro

• Adds balanced_xctest_lifecycle opt-in rule to enforce balanced setUp and tearDown methods in a test class.
  Otavio Cordeiro #3452

• Tweak the auto-correction result console output for clarity.
  mokagio #3522

• Allow configuring related USRs to skip in UnusedDeclarationRule by specifying a list of USRs in the related_usrs_to_skip key. For example you might have custom source tooling that does something with types conforming to a procotol even if that type is never explicitly referenced by other code.
  JP Simard

• Make strong_iboutlet rule correctable.
  MaxHaertwig

• Add legacy_objc_type opt-in rule to warn against using bridged Objective-C reference types instead of Swift value types.
  Blake #2758

• Support Swift Playground control comments in the comment_spacing rule.
  Thomas Goyne

• [Internal] Integrate OS Signposts to help profile SwiftLint performance.
  jpsim

• Update CodeClimateReporter to produce relative paths.
  bmwalters

• Add Bool violation reporting in redundant_type_annotation.
  Artem Garmash #3423

• Add a new capture_variable analyzer rule to warn about listing a non-constant (var) variable in a closure's capture list. This captures the variable's value at closure creation time instead of closure call time, which may be unexpected.
  Laszlo Kustra

• Log references to a specified module when running the unused_import by setting the SWIFTLINT_LOG_MODULE_USAGE=<module-name> environment variable when running analyze.
  jpsim

• Add opt-in rule private_subject rule which warns against public Combine subjects.
  Otavio Cordeiro

Bug Fixes

• Fix custom_rules merging when the parent configuration is based on only_rules.
  Frederick Pietschmann #3468

• Fix misleading warnings about rules defined in the custom_rules not being available (when using multiple configurations).
  Frederick Pietschmann #3472

• Fix bug that prevented the reconfiguration of a custom rule in a child config.
  Frederick Pietschmann #3477

• Fix typos in configuration options for file_name rule.
  advantis

• Fix issue that prevented the inclusion of a configuration file from a parent folder.
  Frederick Pietschmann #3485

• Fix violation location and misplaced corrections for some function references in explicit_self rule.
  JP Simard

• Fix false positives with result builders in unused_declaration.
  JP Simard

• Find more unused declarations in unused_declaration.
  JP Simard

• Fix parsing xcode logs for analyzer rules for target names with spaces.
  JP Simard #3021