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@gabelevi gabelevi released this 13 Apr 22:31
v0.23.0
baa38ff

Likely to cause new Flow errors:

  • When you refine a mixed variable with typeof myVar === 'object', we used to refine the type of myVar to null | Object. Now it is refined to null | {[key: string]: mixed}. This means myVar.prop has the type mixed rather than any.
  • Removed non-standard Promise methods. Previous versions of Flow specified the type of Promise.prototype.done and Promise.cast, which are not standard or implemented in browsers. If you rely on a polyfill that does provide these methods, you can redeclare the Promise class in your project's local libs folder. Note that you need to copy the entire class declaration from lib/core.js in order to add methods and properties. It's not currently possible to extend the builtin declarations, but it is possible to redefine them.

New features:

  • Errors involving union or intersection types now include more information about why the various branches failed
  • flow init now has more command line flags to specify what should be in the created .flowconfig
  • flow ast now can parse JSON files
  • Comments are now supported in .flowconfig files. Lines starting with # or ; are ignored
  • In the [ignore] section of a .flowconfig you can now ignore a relative path with <PROJECT_ROOT>/path/to/ignored
  • Most flow commands have an --ignore-version flag to skip the version check specified in the .flowconfig.
  • Added a module.use_strict option to the .flowconfig. When it is true, Flow will treat every file as if it has the "use strict"; directive.
  • Using strict equality, you can now refine the number type into number literal types. (e.g. after x === 0 Flow now knows that x has the type 0)
  • Flow no longer requires return type annotations for exported functions if Flow can fully infer the type.
  • flow force-recheck FILE1 FILE2 command tells the flow server that FILE1 and FILE2 have changed and that it should recheck. This is intended for tooling that might be racing the file system notifications.
  • Flow is smarter about what !x evaluates to for various types of x.
  • <Foo /> is now allowed when Foo is a string. If $JSXIntrinsics is defined, Foo must be a subtype of $Keys<$JSXIntrinsics>
  • Support for class decorators in addition to property decorators (also gated behind the esproposal.decorators config option). Thanks @marudor!

Notable bug fixes:

  • Disallow (obj: SomeClass) except for when obj instanceof SomeClass
  • Fixed setting temp dir via the .flowconfig
  • Added missing all flag to the .flowconfig
  • Fixed a bug when destructuring a non-literal object type using a pattern with defaults
  • Fixed the --strip-root flag for displaying errors
  • Classes can now have properties named async
  • Fixed refinements like if (foo[0]) { ... }, which should work like if (foo["prop"]) { ... } does. That is, Flow should remember that foo[0] exists and is truthy.
  • Fixed parsing docblocks with CRLF line endings
  • Fixed autocomplete within if statements

Misc:

  • Added more info and structure to JSON output, without removing or existing fields
  • Loads of improvements to the builtin libraries
  • Bunch of perf improvements
  • Clarified some errors messages and error locations
  • flow start --json will start a server and output a JSON blob with info about the new server
  • Slowly improving tracking side effects in switch statements
  • Some improvements to pretty printing errors
  • Object.values() and Object.entries return Array<mixed> and Array<[string, mixed]> respectively, since Flow currently is never sure that it knows about every property in an object.
Assets 4