v0.14.0

Likely to cause new Flow errors:

• Assignment now triggers a refinement. If you have a variable that is a ?string and you assign 'hello' to it, Flow refines its type to 'string'.

Likely to fix old Flow errors:

• We now treat missing type parameters as any. For example, previously ReactElement was treated as ReactElement<*, *, *>. Now it's treated as ReactElement<any, any, any>.

Misc:

• Basic unsafe support for getters & setters, gated behind the config option unsafe.enable_getters_and_setters
• Support for block comments inside of Flow's comment syntax
• Disable by default munging of class property names that start with an underscore, with an option to enable it
• Lots of small internal fixes and merged PRs
• Basic semver support for the .flowconfig version
• Support for declare type in lib files
• Type annotations are now opaque - other types will not flow through them
• You can configure the tmp dir that Flow uses

v0.13.1

Likely to cause new Flow errors:

• Restricted + and += to only allow strings and numbers, and no longer implicitly cast objects, booleans, null or undefined. Use String(x) to explicitly cast these values.
• Fixed a few bugs where types shared between modules may have lost precision or weren't enforced.

Misc:

• Added import typeof feature that allows you to import the type of a value export from another module. It is sugar for: import MyThing_tmp from "MyModule"; type MyThing = typeof MyThing_tmp; (except it removes the need for the intermediate MyThing_tmp variable)
• Added flow ast command to print a serialized JSON ESTree AST. (Note that this AST does not include types, just syntactic structure for now)
• Added support for class expressions
• Added support for following symlinks
• Added support for number-literal and boolean-literal annotations. (useful for things like enum types and refinements based on tests of equivalence between two variables)
• Added support for ES6 binary and octal integer literals
• Added support for export type within a CommonJS module that also uses the module.exports = ... pattern
• Added support for refining some union types down to their disjoint members
• Added support for covariant Promise type parameters
• Added improved support for understanding ES5-style imperative class definitions (i.e. via functions + prototypes)
• Fixed passing undefined to optional parameters
• Fixed return-type tracking for tagged template usage
• Fixed an issue where library parse errors would cause the flow server to continuously restart upon initialization without giving an error

v0.12.0

Likely to cause new Flow errors:

• Fixed a bug where declarations from libraries which are exported from one module are not checked properly in the module into which that module is imported (e.g. if A.foo() returns a Promise, and module B requires A and calls A.foo(), the return type of A.foo() was not being checked properly)
• Fixed enforcement of Object and Function type annotation arity, so that Object<K, V> errors
• Restricted valid computed properties, such that only strings and numbers are allowed (notably, disallows null and undefined)

New features:

• Added support for for-of and support for Iterable interface(s)
• Added support for async/await
• Added structural subtyping for interfaces -- anything can be an instance of an interface as long as it looks right
• Added support for type annotations of the form typeof x, where x is the name of an in-scope variable
• Added a new config option suppress_comment, a regexp which matches against comments and causes any Flow error on the next line to be suppressed. For example, suppress_comment=.*\$FlowFixMe.* will cause /* $FlowFixMe */\nvar x : number = "oops"; to not raise an error.
• Added a new config option module.name_mapper, a regexp -> replacement template tuple to be applied to any matching module names before the Flow system resolves the name and looks it up
• Added a --color=always|never|auto CLI option, useful when piping to less -R
• Added a --one-line CLI option which replaces \n with \\n in multiline error messages, useful when piping to grep

Misc:

• Many improvements to library files, especially node and ES6 APIs
• Improved warnings on unsupported class members [PR #461]
• Added support for export default class
• Fixed if (x instanceof Array)
• Fixed the type of x && y when x is an array, object or function
• Fixed the flow get-def command, especially around imported types
• Fixed a bug with == and improved comparison-related error messages
• Fixed file watching for individual files included via .flowconfig [includes]
• Fixed the build ID, so that the server restarts when accessed from a mismatched client version
• Added a new config option log.file which overrides the default log file path

v0.11.0

• We are now syncing Flow's commit history to GitHub. No more huge updating diffs. We'll also filter the changelog to the most important things.
• Big React refactoring to support ES6 React classes
• Do you use any to workaround things that you want to fix later? Well, now you can use $FixMe instead of any and easily grep for these workarounds later.
• We now report parsing errors in non-@flow files that you are require()'ing/import'ing
• Better error messages and better error message positions
• Better error traces, with flow check --traces N, where N is the trace depth
• Basic support for Object.freeze()
• Assorted fixes and updates to the flow libs
• We're trying to be better about commenting the code

v0.10.0

• Support import/export type
• [PR #412] More fs implementation
• Support for static overloads
• Fix order of args matched with overloads
• Allow methods to have properties
• [PR #405] Make interface-defined modules work with CommonJS/ES6Module interop
• Refine mixed
• Fix typeof null === "object" refinement
• [PR #397] Facilitate debug builds
• [PR #401] Improve error message clarity in a few places
• Remove 'everything is a bool' implicit cast
• Fix issues with optional properties during InstanceT ~> ObjT
• Fix abnormals in catch blocks

v0.9.2

• Fix lowercasing issue where "flow Path/To/Root" became "flow path/to/root"
• Fix "My Path/To Flow/flow path/to/root" not autostarting server due to spaces

v0.9.1

• Unbreak the command line for "flow path/to/root" (thanks @samwgoldman for the report!)

v0.9.0

• Add Video-, Audio and TextTrackList (+ dependencies)
• Refine switch cases
• Better Not_found error
• [PR #333] Partial fs module implementation
• Update parser to match esprima-fb
• [PR #370] Dom canvas context
• [PR #393] Symbol should be called statically. Fix #391
• Fix havoc_env to copy the for_type value
• add bash completion
• rewrite all the commands to use CommandSpec
• json_of_t
• [PR #384] Env printer
• [PR #383] Add some build/test artifacts to .gitignore
• [PR #377] Add missing HTMLImageElement properties
• [PR #367] Re-add merged out oneOfType proptype implementation
• Allow users to pin their .flowconfig to a specific version
• colorize test failure diffs
• Object spread fix
• [PR #322] Add type signature for node "url", "querystring" and "path" modules
• command parsing library
• look for package.json in include paths
• clear module errors properly
• add verbose mode

v0.8.0

• [PR #356] Add React.version to lib/react.js
• [PR #331] node http.get() implementation
• Fixes for indexers in object types and objects used as dictionaries
• Flow server speedup
• Support both commas and semicolons in object type patterns
• Fix object assign for unresolved objects
• Add prerr_endlinef
• Fix support for the mixin pattern of specifying super
• Incremental typechecking fix
• Fix up promises interface definition + more tests
• Perf win by loading master_cx once per job
• Support for-in of null and undefined
• Support typeof x === 'boolean'
• Refine true and false literals
• Fix refinement unit test
• Type declarations for Geolocation interface
• [PR #321] Support for React.cloneElement in 0.13
• Refine simple assignments (things like while (x = x.parent) { x.doStuff(); })

v0.7.0

• Initial support for ES6 import/export (with CommonJS interop)
• Updates to CSS/CSSOM interface definitions
• propTypes in React components now dictate the concrete type signature for this.props
• Show errors in type-at-pos output
• Flow now watches include paths specified in .flowconfig for file changes
• Interpret x != undefined and x != null as the same refinement
• Use Object.prototype.hasOwnProperty() calls as a refinement
• Updates to Element and HTMLElement interface definitions