facebook/flow

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Adds static typing to JavaScript to improve developer productivity and code quality.

Stars: 22.3k
Forks: 1.9k
Open beginner issues: 0
Indexed issues: 510

Dominant language: Rust
License: MIT
Last GitHub push: Sep 15, 2026
Latest indexed: Sep 15, 2026
Contributing guide: Contributing guide
Code of conduct: Code of conduct
Beginner labels: good first issue help wanted
PR merge metrics: No merged PRs in 30d

Open All

510 issues indexed so far

@@-prefixed methods should be allowed only in declarations Open

bug parsing

facebook/flow#2730 · 1 comment · 0 reactions · 0 assignees · Indexed Sep 15, 2026
Type check class that extends class from build in module Open

declarations

facebook/flow#2753 · 0 comments · 1 reaction · 0 assignees · Indexed Sep 15, 2026
Flow declarations requires server restart to fix library parse errors Open

declarations

facebook/flow#2789 · 3 comments · 2 reactions · 0 assignees · Indexed Sep 15, 2026
String substr/substring first argument should be optional Open

Library definitions

facebook/flow#2802 · 0 comments · 0 reactions · 0 assignees · Indexed Sep 15, 2026
Consider more conservative usage of resources Open

enhancement

facebook/flow#2828 · 5 comments · 4 reactions · 0 assignees · Indexed Sep 15, 2026
support symlinks / npm link Open

feature request

facebook/flow#2884 · 4 comments · 29 reactions · 0 assignees · Indexed Sep 15, 2026
How to extract interface from class, exact match Open

feature request Typing: destructors

facebook/flow#2908 · 0 comments · 0 reactions · 0 assignees · Indexed Sep 15, 2026
Flow not checking `new C` when `C` is type `Class<...>` Open

Typing: destructors

facebook/flow#2930 · 4 comments · 0 reactions · 0 assignees · Indexed Sep 15, 2026
Command line option to also check implicit type casting in `number + string` Open

feature request Typing: other

facebook/flow#2941 · 0 comments · 0 reactions · 0 assignees · Indexed Sep 15, 2026
Returning an instance of callee's class with different generic constraint fails Open

feature request

facebook/flow#2959 · 1 comment · 0 reactions · 0 assignees · Indexed Sep 15, 2026
Abstract methods Open

feature request

facebook/flow#2961 · 1 comment · 10 reactions · 0 assignees · Indexed Sep 15, 2026
Should [ignore] apply to name_mapper aliases? Open

facebook/flow#2973 · 0 comments · 0 reactions · 0 assignees · Indexed Sep 15, 2026
bad property not found error related to spread props, object intersections, and import type order Open

Typing: unions/intersections

facebook/flow#2975 · 0 comments · 3 reactions · 0 assignees · Indexed Sep 15, 2026
`PROJECT_ROOT` not supported in .flowconfig -> [libs] Open

bug feature request

facebook/flow#2989 · 5 comments · 3 reactions · 0 assignees · Indexed Sep 15, 2026
Flow should force overriding if a method returns this Open

bug

facebook/flow#2998 · 2 comments · 0 reactions · 0 assignees · Indexed Sep 15, 2026
Possible to create type declarations for extended methods? (i.e., chai plugins) Open

facebook/flow#3018 · 2 comments · 0 reactions · 0 assignees · Indexed Sep 15, 2026
Flow does not accept intersection function types even with disjoint unions Open

feature request Typing: unions/intersections

facebook/flow#3021 · 12 comments · 3 reactions · 0 assignees · Indexed Sep 15, 2026
Type hole with compatibility between optional parameters/extra parameters Open

bug Typing: soundness

facebook/flow#3049 · 4 comments · 2 reactions · 0 assignees · Indexed Sep 15, 2026
Refinement should be lost after function call in loop Open

bug Typing: refinements

facebook/flow#3054 · 0 comments · 2 reactions · 0 assignees · Indexed Sep 15, 2026
--one-line does not work in combination with --from Open

facebook/flow#3068 · 0 comments · 0 reactions · 0 assignees · Indexed Sep 15, 2026
Array destructuring and assignment Open

destructuring enhancement incompleteness

facebook/flow#3073 · 5 comments · 12 reactions · 0 assignees · Indexed Sep 15, 2026
Endless iterator Open

iterators

facebook/flow#3085 · 1 comment · 0 reactions · 0 assignees · Indexed Sep 15, 2026
[libdef] declare module auto-export is too much magic Open

declarations

facebook/flow#3119 · 3 comments · 3 reactions · 0 assignees · Indexed Sep 15, 2026
[Feature request] Allow type imports in module declaration files from user land files Open

feature request

facebook/flow#3122 · 1 comment · 0 reactions · 0 assignees · Indexed Sep 15, 2026
Case sensitivity mismatch leads to "Required module not found" errors Open

bug Windows support

facebook/flow#3125 · 3 comments · 0 reactions · 0 assignees · Indexed Sep 15, 2026
Intersection with disjoint unions generates incorrect invalid access errors Open

needs triage Typing: unions/intersections

facebook/flow#3136 · 0 comments · 0 reactions · 0 assignees · Indexed Sep 15, 2026
Map over an object and using/retaining the type of its properties Open

question

facebook/flow#3140 · 0 comments · 0 reactions · 0 assignees · Indexed Sep 15, 2026
Unexpected error on object intersection Open

facebook/flow#3148 · 0 comments · 0 reactions · 0 assignees · Indexed Sep 15, 2026
Is there any documentation for the JSON API? Open

Needs docs

facebook/flow#3160 · 3 comments · 0 reactions · 0 assignees · Indexed Sep 15, 2026
It doesn't ignore subfolders that contains .flowconfig inside including files. Open

facebook/flow#3161 · 0 comments · 3 reactions · 0 assignees · Indexed Sep 15, 2026
Exact object types shouldn't allow indexer properties Open

Typing: object model

facebook/flow#3162 · 5 comments · 16 reactions · 1 assignee · Indexed Sep 15, 2026
Lower bound of type parameter Open

feature request

facebook/flow#3175 · 1 comment · 0 reactions · 0 assignees · Indexed Sep 15, 2026
Flow Try silently ignores URL when it can't be decoded Open

feature request flow.org

facebook/flow#3182 · 0 comments · 1 reaction · 0 assignees · Indexed Sep 15, 2026
Can't use a class's type as an `extends` Open

facebook/flow#3186 · 1 comment · 3 reactions · 0 assignees · Indexed Sep 15, 2026
module.name_mapper to map absolute import paths no longer works Open

module resolution

facebook/flow#3189 · 5 comments · 7 reactions · 0 assignees · Indexed Sep 15, 2026
Opting in to getter/setter usage still fails with 'Contravariant property incompatible with covariant use' Open

facebook/flow#3191 · 2 comments · 0 reactions · 0 assignees · Indexed Sep 15, 2026
Reuse flow class declaration for class definition Open

facebook/flow#3193 · 8 comments · 2 reactions · 0 assignees · Indexed Sep 15, 2026
`Class` should be invariant Open

Typing: object model

facebook/flow#3201 · 4 comments · 0 reactions · 0 assignees · Indexed Sep 15, 2026
Suppress unused suppression errors after a library parse error. Open

facebook/flow#3210 · 1 comment · 6 reactions · 0 assignees · Indexed Sep 15, 2026
get [Symbol.toStringTag]() : string and Object.prototype.toString.apply Open

facebook/flow#3212 · 0 comments · 2 reactions · 0 assignees · Indexed Sep 15, 2026
Weird grammar with function types and intersections Open

parsing

facebook/flow#3256 · 0 comments · 0 reactions · 0 assignees · Indexed Sep 15, 2026
Flow doesn't like Symbols as object keys Open

feature request incompleteness Typing: object model

facebook/flow#3258 · 25 comments · 49 reactions · 0 assignees · Indexed Sep 15, 2026
Parser recovers badly when function declaration is missing identifier Open

parsing

facebook/flow#3300 · 0 comments · 0 reactions · 0 assignees · Indexed Sep 15, 2026
`Function` has no callable signature Open

enhancement Typing: completeness

facebook/flow#3317 · 3 comments · 3 reactions · 0 assignees · Indexed Sep 15, 2026
EventEmitter when inherited deeply does not respect parent type Open

facebook/flow#3329 · 0 comments · 2 reactions · 0 assignees · Indexed Sep 15, 2026
Inline if ignores object types Open

facebook/flow#3338 · 3 comments · 2 reactions · 0 assignees · Indexed Sep 15, 2026
How to properly reference flow-typed in custom type declarations? Open

facebook/flow#3339 · 1 comment · 0 reactions · 0 assignees · Indexed Sep 15, 2026
Please consider running tryFlow code in web worker Open

feature request flow.org

facebook/flow#3362 · 3 comments · 2 reactions · 0 assignees · Indexed Sep 15, 2026
Intersection type incompatible with equivalent type Open

facebook/flow#3363 · 1 comment · 0 reactions · 0 assignees · Indexed Sep 15, 2026
Flow reports implicitly returned undefined even when not possible Open

bug

facebook/flow#3366 · 2 comments · 8 reactions · 0 assignees · Indexed Sep 15, 2026

facebook/flow

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